GE Industrial Solutions ML-18, ML-18H User Manual
GEK-86132G Instructions
g
PowerVac
®
Vacuum Circuit Breaker
with ML-18 or ML-18H Mechanism
_______________________________________________________________________________
1
PowerVac ® Vacuum Circuit Breaker
With ML-18 or ML-18H Mechanism
Table of Contents
Description Page
Description Page
SECTION 1 Introduction.............................................. 4
1.1 Safety .............................................................................. 4
1.2 Maintenance ................................................................... 4
SECTION 2 Description................................................ 5
2.1 General............................................................................ 5
2.2 Summary Description ...................................................... 5
SECTION 3 Receiving, Handling and
Storage...................................................... 5
3.1 Receiving ........................................................................ 5
A. Equipment Packages................................................. 5
B. Inspecting for Damage .............................................. 5
C. Filing a Claim............................................................. 5
3.2 Handling .......................................................................... 5
3.3 Storage............................................................................ 5
SECTION 4 Features....................................................... 6
4.1 Safety Precautions........................................................... 6
4.2 Interlocks......................................................................... 6
4.2.1 Rating Interference Plate................................................. 6
4.2.2 Closing Spring Interlock ................................................... 7
4.2.3 Negative Interlock............................................................ 7
4.2.4 Positive Interlock Bar....................................................... 7
4.2.5 Closing Spring Gag Interlock............................................ 7
SECTION 5 Operation ................................................... 8
5.1 General............................................................................ 8
5.2 Close Spring Charging ..................................................... 8
5.3 Closing Operation............................................................ 8
5.4 Opening Operation.......................................................... 9
5.5 Trip-free Operation.......................................................... 9
SECTION 6 Control Circuit........................................ 9
SECTION 7 Mechanical Checking and
Slow Closing......................................... 9
7.1 Visual Inspection.............................................................. 9
7.2 Closing Spring Charging ..................................................10
7.3 Closing Spring Gag ..........................................................10
7.4 Slow Closing....................................................................10
7.5 Gag Plate Removal..........................................................10
SECTION 8 Dimensional Checks..........................11
8.1 Primary Contact Erosion ..................................................11
8.2 ML-18 Wipe Spring Compression....................................11
8.3 ML-18H Wipe Spring Compression .................................11
8.4 Contact Gap ....................................................................11
8.5 Coil Plunger Gap..............................................................11
8.6 Control Switch Adjustment..............................................12
8.6.1 LCS and SM/LS Switch Adjustment.................................12
8.6.2 CL/MS Switch Adjustment ..............................................12
8.6.3 IL/MS Switch Adjustment................................................13
SECTION 9 Electrical Checks .................................. 14
9.1 Electrical Operation......................................................... 14
9.2 High Potential Test.......................................................... 14
9.2.1 Primary Circuit................................................................. 14
9.2.2 Secondary Circuit ............................................................ 14
9.3 Primary Circuit Resistance ..............................................14
9.4 Vacuum Interrupter Integrity Test.................................... 14
9.5 Insulation Test.................................................................15
SECTION 10 Checking and Installing
Breakers.................................................16
SECTION 11 Maintenance......................................... 17
11.1 General ...........................................................................17
11.1.1 PowerVac Interrupter ...................................................... 17
11.1.2 Trouble Reporting ........................................................... 17
11.2 Service Conditions ..........................................................17
11.3 Fault Interruptions ........................................................... 17
11.4 Contact Erosion...............................................................17
11.5 Transfer Finger Wear ...................................................... 17
11.6 Mechanism ..................................................................... 17
11.7 Primary Insulation Parts................................................... 17
11.8 Lubrication ...................................................................... 18
11.9 Recommended Maintenance.......................................... 18
SECTION 12 Timing........................................................ 19
SECTION 13 Opening and Closing Speed ... 20
SECTION 14 Repair and Replacement ............ 21
14.1 General ...........................................................................21
14.2 Replacement of Interrupter Assemblies .........................21
14.3 Primary Disconnect Fingers ............................................ 21
14.4 Mechanism ..................................................................... 21
14.5 Control Switches............................................................. 21
14.6 Trip Coil Replacement..................................................... 21
14.7 Closing Coil Replacement............................................... 22
14.8 Auxiliary Switch Replacement......................................... 22
14.9 Motor Replacement........................................................ 22
14.10 “Y” Relay Replacement ................................................... 22
SECTION 15 Renewal Parts ..................................... 23
15.1 Ordering Instructions....................................................... 23
SECTION 16 Mechanical Adjustment.............. 23
16.1 General ...........................................................................23
16.2 Wipe Adjustment ............................................................ 23
16.3 Contact Gap Adjustment................................................. 23
16.4 Trip Coil Plunger.............................................................. 24
16.5 Close Coil Plunger........................................................... 24
16.6 Close Latch Stop Bolt......................................................24
16.7 Closing Spring Discharge Interlock.................................. 24
16.8 Negative Interlock ........................................................... 24
INDEX ........................................................................................ 37
Trouble Reporting Form................................................................ 39
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List of Illustrations
Figure Page
1 Front view of PowerVac® breaker with front cover ................... 6
2 Rating interference plate........................................................... 6
3 Front view of PowerVac breaker without front cover ................ 8
4 Manual charging........................................................................ 9
5 Gag plate installation .................................................................10
6 Operating rod assembly ............................................................10
7 Contact gap...............................................................................11
8 Breaker turned on right side......................................................11
9 Close coil plunger gap ...............................................................12
10 Trip coil plunger gap..................................................................12
11 Control switches .......................................................................13
12 Sample operating speed graphs................................................19
13 Contact gap adjustment ............................................................20
14 Auxiliary switch position............................................................22
15 Spring discharge interlock .........................................................24
16 Toggle linkage positions of the ML-18 mechanism ...................25
17 Schematic of ML-18 mechanism...............................................27
18 Typical wiring diagram for ML-18 mechanism...........................29
19 PowerVac® breaker left-front view ............................................30
20 PowerVac® breaker right-rear view ...........................................30
21 Trip coil and linkage...................................................................31
22 Close coil linkage.......................................................................32
23 Bottom view of the ML-18 mechanism.....................................33
24 Flex cable connections..............................................................34
25 Negative interlock .....................................................................34
26 Close latch stop.........................................................................35
27 Wipe spring...............................................................................35
THESE INSTRUCTIONS ARE INTENDED FOR USE BY QUALIFIED PERSONNEL FOR INSTRUCTION AND MAINTENANCE PURPOSES.
REPRODUCTION IN WHOLE OR IN PART IS NOT PERMITTED WITHOUT THE EXPRESS PERMISSION OF GENERAL ELECTRIC.
Table Page
1 Control Device and Voltage..................................................... 18
2 Measurements ....................................................................... 36
3 Adjustments............................................................................ 36
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PowerVac ® Vacuum Circuit Breaker
With ML-18 or ML-18H Mechanism
SECTION 1—Introduction
This manual provides the information needed by the user to
properly install, operate and maintain the ML-18 or ML-18H
PowerVac® Breaker.
The PowerVac® vacuum breaker is a horizontal drawout,
removable and interchangeable interrupting element for use
in metalclad switchgear to provide protection and control of
electrical apparatus and power systems. To the extent
required applicable ANSI, IEEE and NEMA Standards are met.
No such assurances are given with respect to local codes and
ordinances, as they vary greatly.
1.1—Safety
Each user must maintain a safety program for the protection
of personnel, as well as other equipment, from the potential
hazards associated with electrical equipment.
The following requirements are intended to augment the
user's safety program, but NOT supplant the user's
responsibility for devising a complete safety program. The
following basic industry practiced safety requirements are
applicable to all major electrical equipment such as switchgear
or switchboards. GE neither condones nor assumes any
responsibility for practices which deviate from the following:
1. ALL CONDUCTORS MUST BE ASSUMED TO BE
ENERGIZED UNLESS THEIR POTENTIAL HAS BEEN
MEASURED AS GROUND AND ADEQUATE CAPACITY
GROUNDING ASSEMBLIES HAVE BEEN APPLIED TO
PREVENT ENERGIZING. Many accidents have been
caused by unplanned energization from non-recognized
back feeds, equipment malfunctions, and from a wide
variety of sources.
2. VACUUM CIRCUIT BREAKERS ARE NOT TO BE
CONSIDERED AS AN ISOLATING MEANS FOR
PROVIDING SAFETY TO PERSONEL UNLESS
WITHDRAWN TO FULLY “DISCONNECTED/TEST”
POSITION. In the “CONNECTED” position with the
interrupter contacts separated (breaker open), small
leakage current with high voltages can flow across the
gap. In addition, leakage current can flow across the
bottle or interrupter assembly if dirty or high humidity is
providing a path for tracking.
3. It is strongly recommended that all equipment be
completely de-energized, verified to be “dead”, then
grounded with adequate capacity grounding assemblies
prior to any maintenance. The grounding cable
assemblies must be able to withstand energizing fault
levels so that protective equipment may clear the circuit
safely. Additional discussion on this concept is covered in
Chapter 20 of ANSI/NFPA 70B, Electrical Equipment
Maintenance.
4. Although interlocks to reduce some of the risks are
provided, the individual's actions while performing service
or maintenance are essential to prevent accidents. Each
person's knowledge; mental awareness; and planned and
executed actions often determine if an accident will
occur. The most important method of avoiding accidents
All personnel associated with installation, operation and
maintenance of electrical equipment, such as power circuit
breakers and other power handling equipment, must be
thoroughly instructed, with periodic retraining, regarding
power equipment in general as well as the particular model of
equipment with which they are working.
Instruction books, actual devices and appropriate safety and
maintenance practices such as OSHA publications, National
Electric Safety Code (ANSI C2), National Electric Code, and
National Fire Protection Association (NFPA) 70B Electrical
Equipment Maintenance must be closely studied and
followed. During actual work, supervision should audit
practices to assure conformance.
1.2—Maintenance
Excellent maintenance is essential for reliability and safety of
any electrical equipment. Maintenance programs must be
tuned to the specific application, well planned and carried out
consistent with both industry experience and manufacturer's
recommendations. Local environment must always be
considered in such programs, including such variables as
ambient temperatures, extreme moisture, number of
operations, corrosive atmosphere or major insect problems
and any other unusual or abusive condition of the application.
One of the critical service activities, sometimes neglected,
involves the calibration of various control devices. These
monitored conditions in the primary and secondary circuits,
sometimes initiating emergency corrective action such as
opening or closing circuit breakers. In view of the vital role of
these devices, it is important that a periodic test program be
followed. As was outlined above, it is recognized that the
interval between periodic checks will vary depending upon
environment, the type of device and the user's experience.
It is the GE recommendation that, until the user has
accumulated enough experience to select a test interval
better suited to the individual requirements, all significant
calibrations be checked at an interval of one to two years.
To accomplish this, some devices can be adequately tested
using test sets. Specific calibration instructions on particular
devices typically are provided by supplied instruction books.
Instruction books supplied by manufacturers address
components that would normally require service or
maintenance during the useful life of the equipment.
However, they can not include every possible part that could
under adverse environments. Maintenance personnel must
be alert to deterioration of any part of the supplied
switchgear, taking actions, as necessary to restore it to
serviceable status.
Industry publications of recommended maintenance practices
such as ANSI/NFPA 70B, Electrical Equipment Maintenance,
is for all associated personnel to carefully apply a
thorough under-standing of the specific equipment from
the viewpoints of its purpose, its construction, its
operation and the situations which could be hazardous.
4
should be carefully studied and applied in each user's
formation of planned maintenance.
Some users may require additional assistance from GE in the
planning and performance of maintenance. Local GE Sales
can be contracted to either undertake maintenance or to
provide technical assistance such as the latest publications.
SECTION 2—Description
2.1—General
This section contains a description of the PowerVac® vacuum
circuit breaker. It also describes the functions of the electrical
and mechanical systems.
2.2—Summary Description
The PowerVac
power interrupters to establish and interrupt a primary circuit.
Primary connections to the associated metalclad switchgear
are made by horizontal bars and disconnect fingers,
electrically and mechanically connected to the vacuum
interrupters. Molded interrupter supports, one per phase on a
three-phase circuit breaker, provide mountings for the primary
bars, interrupters, current transfer fingers, and heat
dissipation fins (where used). The operating mechanism
provides direct motion at each phase location in order to
move the movable contact of the vacuum interrupters from an
open position to a spring-loaded closed position and then back
to the open position on command.
®
vacuum circuit breaker uses sealed vacuum
The performance and safety of all equipment may be
compromised by the modification of supplied parts or their
replacement by non-identical substitutes. All such design
changes must be qualified to the original manufacturers
specifications.
The user should methodically keep written maintenance
records as an aid in future service planning and equipment
reliability improvement. Unusual experiences should be
promptly communicated to G.E.
The ML-18 and ML-18H mechanisms are of the stored-energy
type and use a gear motor to charge a closing spring. During a
closing operation, the energy stored in the closing spring is
used to close the vacuum interrupter contacts, compress the
wipe springs which load the contacts, charge the opening
spring, and overcome bearing and other friction forces, The
energy then stored in the wipe springs and opening spring will
open the contacts during an opening operation.
Closing and opening operations are controlled electrically by
the metalclad switchgear or remote relaying. Mechanical
control is provided by manual close and trip buttons on the
circuit breaker. The closing spring may be manually charged,
and a method for slow-closing the primary contacts is
available. The mechanism will operate at the ac or dc voltage
indicated on the circuit breaker nameplate.
Mechanical and electrical interlocks are provided and are
described in Section 4.2, Interlock.
SECTION 3—Receiving, Handling and Storage
3.1—Receiving
A. Equipment Packages
Every package leaving the factory is plainly marked with the
case number, requisition number, and customer’s order
number. If the equipment has been split for shipment, the
section numbers of the equipment enclosed in each shipping
package are identified.
NOTE: To avoid loss of any parts when unpacking, the
contents of each container should be carefully checked
against the packing list before discarding the packing material.
Contents of each shipping package are listed on the Master
Packing List. In addition, this list includes the number of the
shipping crate in which miscellaneous parts needed to install
and operate equipment (such as hardware, contact lubricant,
touch-up paint, breaker closing devices, etc.) are located.
Normally, such devices are packed in a cardboard carton and
the carton secured in an empty switchgear compartment. If
such items are packed in a switchgear section instead of a
separate crate, the list will indicate appropriate section
number in which they are stored. Large items (such as
breaker lift trucks used with indoor and outdoor equipment)
will always be shipped in separate crates or cartons.
B. Inspecting for Damage
All equipment leaving the factory is carefully inspected and
packed by personnel experienced in the proper handling and
packing of electrical equipment. Upon receipt of any
equipment, immediately perform a visual inspection to
ascertain if any damage has been sustained in shipping or if
there are any loose parts.
C. Filing a Claim
If any damage is evident, or indication of rough handling is
visible, file a claim for damage at once with the transportation
company and notify the nearest General Electric Company
Sales Office immediately. Information on damaged parts, part
number, case number, requisition number, etc., should
accompany the claim.
3.2—Handling
When lifting the breaker, use of the specially designed lift
truck is recommended. It is necessary to use the lift truck
when placing a breaker into or removing it from the metalclad
switchgear unless the breaker is equipped with a roll-in
undercarriage (bottom only) . If it is necessary to lift the
breaker with a hoist use four 1/2 inch diameter hooks rated at
least 500 pounds each. Lifting locations are provided in the
side frame members. Use a spreader wider than the breaker
to prevent slings from contacting the interrupter supports.
3.3—Storage
It is recommended that the breaker be put immediately in its
permanent location. If this is not possible, the following
precautions must be taken to assure proper breaker storage.
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1. The breaker should be protected against condensation,
preferably by storing it in a warm dry room of moderate
temperature such as 40° - 100°F. Circuit breakers for
outdoor metalclad switchgear should be stored in the
equipment only when power is available and the heaters
are in operation to prevent condensation.
2. The breaker should be stored in a clean location, free
from corrosive gases or fumes; particular care, for
example, should be taken to protect the equipment from
moisture and cement dust, as this combination is present
SECTION 4—Features
4.1—Safety Precautions
This circuit breaker uses powerful springs for energy storage.
WARNING: DO NOT WORK ON THE INTERRUPTERS OR THE
MECHANISM UNLESS THE CIRCUIT BREAKER IS IN THE
“OPEN” POSITION AND BOTH THE CLOSING AND OPENING
SPRINGS ARE EITHER “DISCHARGED” OR GAGGED AND ALL
ELECTRICAL POWER IS REMOVED.
These precautions are required to prevent accidental operation.
Anyone working on the circuit breaker should be familiar with
the contents of this instruction book.
2 2
3
2
5
9
Figure 1 Front view of PowerVac breaker
with front cover
1. Front cover 6. Manual charge lever
2. Cover mounting bolts 7. Counter
3. Manual trip button 8. Spring charge indication
4. Manual close button 9. Closing spring gag access
5. Nameplate 10. Open/Close indicator
The circuit breaker has been shipped in the “CLOSED” position.
After removing packing material, open the breaker by pushing in
firmly on the manual trip button (item 3, Figure 1), while
keeping hands away from moving parts, and verify that the
operation counter advances one count.
Closing and opening springs are now in their discharged
positions. Check this by first pressing the manual close button,
then the manual trip button. The indicator flags on the front of
the breaker should show “OPEN” and “DISCHGD”. All
mechanical and electrical checks should be completed before
putting breakers in service.
4.2—Interlocks
Each PowerVac® vacuum circuit breaker is provided with the
following interlocks:
4.2.1 Rating Interference Plate
This interlock (item1, Figure 2) permits only a breaker with a
matching continuous current, voltage and interrupting rating to
be inserted into a metalclad compartment of identical rating.
1
10
7
2
1. Rating interference plate
2. Lifting locations (3/4” dia. hole at all four corners)
An option available is the combination 1200/2000 ampere
breaker, which can be used in either a 1200 or 2000 ampere
compartment. The rating interference plate must be adjusted to
match the current rating of the compartment. This adjustment is
done by positioning the outer interference plate so that the
edge of the plate lines up with the current indicated on the label
attached to the breaker just above the rating interference plate.
at construction sites and has a very corrosive effect on
many parts.
3. Rollers, latches, etc., of the operating mechanism should
be coated with 0282A2048P009 grease to prevent
rusting.
If the breaker is stored for any length of time, it should be
inspected periodically to see that rusting has not started and
to ensure good mechanical condition. Should the breaker be
stored under unfavorable atmospheric conditions, it should be
cleaned and dried out before being placed in service.
2
1
Figure 2 Rating interference plate
6
4.2.2 Closing spring interlock
This racking-track operated interlock (item 4, Figure 20)
prevents racking into or out of the metalclad compartment a
breaker that has the closing spring charged. This action is
accomplished by a roller on the right side of the breaker.
Mechanism, which contacts the racking mechanism and
discharges the closing spring, unless the breaker is in the
“DISCONNECT/TEST” position or the “CONNECT” position in
the metalclad compartment. This interlock also opens the
CL/MS switch in the motor circuit to prevent electrical
charging of the closing spring when the breaker is between
the “DISCONNECT/TEST” and “CONNECT” position in the
metalclad compartment.
4.2.3 Negative Interlock
The function of this racking-track operated interlock (item5,
Figure 19) is to remove the trip latch from the trip roller
thereby preventing a closing operation. The interlock also
opens the LCS switch in the closing circuit thereby removing
the close circuit power. The negative trip interlock is
functional while the beaker is being moved between the
“DISCONNECT/TEST” and “CONNECT” position and upon
withdrawal from the metalclad compartment.
4.2.4 Positive Interlock Bar
This interlock will prevent the racking of a closed breaker into
or out of a metalclad compartment. A linkage connected to
the cross shaft extends a détente angle (item 3, Figure 19)
out through the left side of the mechanism frame when the
breaker contacts are in the closed position. If the breaker is in
the “CONNECT” or “DISCONNECT/TEST” position in the
metalclad the détente angle locks into the racking mechanism
to prevent access to the hex section of the racking screw.
4.2.5 Closing Spring Gag Interlock
The interlock is provided to prevent a breaker that has a
gagged closing spring from entering a metalclad unit. This
function is accomplished by projecting an angle (item1, Figure
19) out of the left front side of the mechanism when the
closing spring is gagged. This angle will interfere with the
racking mechanism and block entry into the metalclad unit
when the Closing Spring Gag Access Door is open.
7
4
7
9
13
SECTION 5—Operation
5.1—General
The PowerVac
power interrupters to establish and interrupt a primary circuit.
Primary connections to the associated metalclad switchgear are
made by horizontal bars and disconnect fingers, electrically and
mechanically connected to the vacuum interrupters. Molded
interrupter supports, one per phase on a three-phase circuit
breaker, provide mountings for the primary bars, interrupters,
current transfer fingers, and heat dissipation fins (where used).
The operating mechanism provides direct motion at each phase
location in order to move the lower contact of the vacuum
interrupters from an open position to a spring-loaded closed
position and then back to the open position on command.
The ML-18/18H mechanism (Figure 17) is of the stored-energy
type and uses a gearmotor to charge a closing spring. During a
closing operation, the energy stored in the closing spring is used
to close the vacuum interrupter contacts, compress the wipe
springs which load the contacts, charge the opening spring, and
overcome bearing and other friction forces, The energy then
stored in the wipe springs and opening spring will open the
contacts during an opening operation.
Closing and opening operations are controlled electrically by the
metalclad switchgear or remote relaying. Mechanical control is
provided by manual close and trip buttons on the circuit breaker.
The closing spring may be manually charged, and a method for
slow-closing the primary contacts is available. The mechanism
will operate at the ac or dc voltage indicated on the circuit
breaker nameplate.
5.2—Close Spring Charging
Figure 17 shows a front view of the ML-18 in a schematic form.
The primary contacts are open and the closing spring is charged.
The closing spring charging system consists of a closing spring
(item 1, view B) mounted on the left side of the breaker and the
electrical charging system mounted on the right side of the
breaker. Both components are fastened to the cam shaft (item
2, view B). A manual charging system (item 3, view A) is
provided so that the mechanism can be slow closed and the
closing spring can be charged if there is a loss of electrical
control power.
Spring charging is accomplished electrically by a rotating
eccentric on the output shaft of the gear motor driving pivoted
charging arms (item 4, view C) which oscillate about the
centerline of a ratchet wheel (item 5, view C). A driving pawl
(item 6, view C), mounted within the charging arms, oscillates
with the charging arms. Starting from its rear-most position, as
the charging arms rotate forward, a spring forces engagement
of the driving pawl with a tooth of the ratchet wheel. The
ratchet wheel is advanced by the rotating charging arms and
pawl assembly. Advancement of one tooth spacing is provided
for each oscillation of the system. The ratchet motion is
restricted to one direction by a spring-loaded holding pawl that
prevents the ratchet wheel from going backwards as the
charging arms oscillate back to pick up the next tooth. Thirteen
complete cycles of the charging arms are needed for a full
charge of the closing spring. The efficient, compact gear motor
accomplishes this action in about two seconds. When the
charging cycle is complete, the ratchet wheel is positioned so
®
vacuum circuit breaker uses sealed vacuum
that a missing tooth is adjacent to the driving pawl and any
motor over spin will not drive the ratchet wheel, thus preventing
damage to the system.
When the spring is completely charged, the assembly is
retained in that position by the close latch, until it is desired
to close the circuit breaker.
The closing coil cannot be electrically energized unless the
closing spring is completely charged. This action is prevented by
the 52/CHG switch in the closing circuit.
The manual charging system (item 3, view A) works directly on
the cam shaft where a one-way clutch (item 7, view A), driven
by a manual handle, provides rotation of the ratchet wheel.
Manual pumping of the handle advances the ratchet wheel and
the holding pawl prevents counter-rotation while the handle is
returning for another stroke. Approximately eight complete
strokes of the manual handle are required for one complete
spring-charging operation. When the spring charge indicator
(item 9, Figure 3) shows “CHARGED”, MANUAL CHARGING
MUST BE DISCONTINUED TO AVOID MECHANISM DAMAGE.
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1
2
12
3
4
5
8
11
10
Figure 3 Front view of PowerVac breaker
without front cover
1. Upper interrupt connection 8. Counter
2. Interrupter support 9. Spring charge indication
3. Operating rod 10. Manual charge lever
4. Racking arm 11. Manual close button
5. Compartment track rollers 12. Secondary disconnect
6. Manual trip button handle
7. Open/Close indicator 13. Closing spring gag access
5.3—Closing Operation (Refer to Figure 17)
By either energizing the close solenoid or depressing the
manual close button, the close latch (item 8, view C) is rotated,
releasing the closing spring (item 1, view B). This
action releases the energy in the closing spring and transmits it
to the closing cam (item 9, view D) and closing roller (item 10,
view D) and causes the linkage to rise until the prop (item 11,
view D) can slip under the close roller (item 10, view D) and
hold the linkage in place. As the linkage moves, the output crank
(item 12, view D) rotates the cross shaft (item 13, view D)
which in turn rotates the phase bell cranks and compresses the
two opening springs (item 15, view E) on poles 1 and 3, this
closes the vacuum interrupters, and compresses the wipe
springs (item 16, view E) on each pole.
The rotation of the cross shaft (item 13, view D) also changes
the auxiliary switch (item 7, view D) position. The position flag
on the front panel will then indicate “CLOSED”. After the breaker
8
is closed, the charging motor is again energized and the closing
spring is charged as described under “CLOSED SPRING
CHARGING”. Spring charging is possible when the breaker is in
the closed position because the linkage is held in place by the
prop.
5.4—Opening Operation (refer to Figure 17)
By either energizing the trip solenoid or depressing the manual
trip button (item 23, view B), the trip latch (item 19, view D) is
rotated, permitting the linkage to collapse and the vacuum
interrupter contacts to open under the force of the wipe springs
(item 16, view E) and opening springs (item 15, view E). At the
end of the opening stroke, the center phase wipe spring
assembly hits a stop block on the frame that limits overtravel
and rebound. Rotation of the cross shaft from the closed to the
open position operates the auxiliary switch (item 17, view D)
which opens the trip coil circuit. If the closing spring has been
recharged, the linkage will be reset and the trip latch will be in
place on the trip roller, ready for another closing operation.
5.5—Trip-free Operation
The linkage is mechanically trip free in any location on the
closing stroke. Electrically energizing the trip coil while closing
will, after the auxiliary switch contacts change position, rotate
the trip latch and permit the circuit breaker to open fully.
The linkage will reset as in a normal open operation, and the
closing spring will recharge as described under SPRING
CHARGING.
SECTION 6—Electric Control circuit
A typical PowerVac® circuit breaker ML-18 or ML-18H mechanism
wiring diagram is shown in Figure 16. Check the wiring diagram
supplied with the actual circuit breaker for its wiring.
The close spring-charging motor circuit is established through
the CL/MS (close latch monitor switch) switch if the close latch
is reset and the SM/LS (spring motor limit switch) if the closing
spring is discharged. When the closing spring is charged, the
SM/LS interrupts the circuit.
The IL/MS switch is connected to sense position of negative
interlock. When the breaker is racked between the connect and
disconnect position, the negative interlock roller is depressed as
a result the IL/MS switch is open and does not allow the motor
to charge the closing spring. Once the breaker is rack in the
switch closes allowing the spring charge motor to charge the
closing spring.
The close coil circuit is established through two normally closed
52Y relay contacts, and the latch-checking switch LCS, if the trip
latch is reset. An auxiliary switch contact 52b is also in series
with the close coil and closes when the breaker is
open and opens when the breaker is closed. During a close
operation, cam rotation closes the SM/LS contact allowing the
52Y relay to be energized; opening its contacts in the close coil
circuit and sealing itself in through one of its own contacts to
the close signal. This seal-in action prevents re-closing on a
sustained close command as the close signal must be removed
to drop out the Y relay, and reestablish the close circuit, thereby
providing an anti-pump feature.
Circuit breaker mounted auxiliary switch contacts not used in
the control circuit are bought out for control and indication
functions. The metalclad equipment may provide a breaker
operated stationary auxiliary switch for additional contacts
(3, 6 or 10 stages are available.
SECTION 7—Mechanical Checking and Slow Closing
7.1—Visual Inspection
Visually inspect the circuit breaker for any signs of damage or
loose hardware.
7.2—Closing Spring Charging
Manually charge the breaker closing spring using the charging
handle provided (item 1, Figure 4). The closing spring is charged
by a ratcheting mechanism that advances by one ratchet tooth
at a time. When the spring is fully charged and the spring load is
held by the closing latch, the spring indicator (item 3, Figure 1)
will change from “DISCHGD” to “CHARGED”, and a positive snap
will be heard as the spring travels over center.
CAUTION: AFTER THE SPRING IS COMPLETELY CHARGED,
AS INDICATED IN FIGURE 4, FURTHER FORCING CHARGING
HANDLE MAY CAUSE DAMAGE TO THE CLOSING LATCH AND
ITS ASSOCIATED PARTS.
1. Manual charging handle
2. Close spring gag hole
(Shown in closed position)
3. Spring charge indication
Figure 4 Manual charging
3
2
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Figure 5 Gag plate
2
1
1 -- Closing spring gag plate
2 -- Manual charging lever
7.3—Closing Spring Gag
Insert the closing spring gag plate (item1, Figure 5) by opening
the closing spring gag hole cover and inserting the tip of the gag
plate between the end of the spring and the spring guide and
engaging the détentes on the gag plate into the slots in the
closing spring guide. Note that when the closing spring guide is
charged for gagging, an interference angle is exposed on the
left side of the breaker (item 3, Figure 19). With the closing
spring in the gagged position, this angle will provide
interference preventing use of the lift truck and racking of the
breaker element. No attempt should be
made to alter, modify or otherwise make inoperative this safety
feature. With the gag plate in position, depress the manual
close button. This action will partially discharge the closing
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5
11
1
spring and also partially close the vacuum interrupter contacts.
Do not energize the secondary control circuit at this time.
7.4—Slow Closing
To manually slow close the breaker contacts, install the closing
spring gag, as described above, and push the manual close
button (item 11, Figure 3).
CAUTION: FAILURE TO PUSH THE CLOSE BUTTON BEFORE
CONTINUING THE SLOW CLOSE PROCEDURE WILL CAUSE
DAMAGE TO THE MECHANISM.
After pushing the manual closing button, put the manual charge
handle on the manual charge lever and move the handle up and
down. The breaker will be fully closed when the spring charge
indicator shows “CHARGED”.
CAUTION: WITH THE GAG PLATE INSTALLED, THE BREAKER
CLOSED, AND OPENING SPRINGS CHARGED, THE BREAKER
CAN BE TRIPPED AT FULL SPEED.
7.5—Gag Plate Removal
To remove the gag plate, the closing spring must be fully
charged. If the spring charge indicator does not show
“CHARGED” in the window, manually charge the spring until
it does. Lift up and push in on the gag plate to clear the
détentes on the gag plate from the slots in the closing spring
guide. While holding the gag plate up, remove it from the
opening. Close the gag hole cover. For safety, first close the
breaker by depressing the manual “CLOSE” button and then
depress the manual “TRIP” button. All stored energy is now
removed from the breaker.
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8
7
6
4
3
2
Figure 6 Operating rod assembly
1. Wipe spring 5. Lock washer 9. Clamp screws
2. Wipe indicator (ML 18 only) 6. Hexagon projection 10. Interrupter movable contact rod
3. Erosion disk 7. Operating rod insulator 11. Reference arm
4. Lock nut 8. Coupling clamp
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SECTION 8—Dimensional Checks
With the breaker closed and the gag plate installed, perform
the following dimensional checks.
8.1—Primary Contact Erosion
In the closed position, the erosion disk (item 3, Figure 6)
below the operating rod insulator is aligned with a reference
arm (item11, Figure 6) on new interrupters. As contact
erosion occurs, the erosion disk will move upward from
alignment with that reference arm. When erosion reaches 1/8
inch, the PowerVac® interrupters should be replaced. DO NOT
RE-ADJUST THE ALIGNMENT OF THE EROSION INDICATOR
ARM EXCEPT WHEN INSTALLING A NEW VACUUM
INTERRUPTER.
8.2—ML-18 Wipe Spring Compression
With the breaker closed and the closing spring gagged,
measure with a feeler gauge and record the distance
between the top of the wipe indicator and the bottom of the
erosion disk for each phase (see Figure 27, Dimension W).
Trip the breaker with the closing spring gag plate still installed
and measure and record the distance between the wipe
indicator and erosion disk. Subtract the closed position
measurement from the open position measurement. The
result is the amount of wipe on each individual pole. The wipe
is to be greater than 0.075 inch. Adjustment is not required
until wipe is 0.075 inch or less. If adjustment is required see
WIPE ADJUSTMENT in MECHANICAL ADJUSTMENT section.
The ML-18 and ML-18H mechanisms are furnished with very
low gradient wipe springs so that adjustment is not a
precision operation and considerable loss of wipe can be
tolerated without affecting performance.
8.3—ML-18H Wipe Spring Compression
With the breaker closed and the closing spring gagged,
Figure 7 Contact gap
measure with a feeler gauge and record the distance
between the bellville washer and the trunion between the bell
crank arms.
8.4—Contact Gap
The method of measuring the contact gap is as follows: With
the breaker in the open position, the closing springs charged,
and the closing spring gag plate installed, apply a piece of
masking tape to the surface of the operating rod insulator as
shown in Figure 7. Using a reference block, make a mark on
the tape near the top on all three poles. It is also advisable to
put a reference mark on the tape to identify to which pole the
tape is applied. Remove the closing spring gag plate and
close the breaker. Using the same procedure as above, remark the tape. This new mark will be near the bottom of the
tape. Trip the breaker, remove the tapes and re-apply them to
a flat surface. Measure the distance between the two lines.
A caliper will give an accurate reading of the contact gap,
Dimension G: The gaps must be between the 0.60 inch
maximum at the center pole and 0.54 inch minimum at the
outer poles. It is not necessary that all readings correspond. A
properly adjusted breaker will have more gap and wipe on the
center pole than on the outside poles.
8.5—Coil Plunger Gap
The close coil and trip coil plunger gap dimensional checks are
made in the operating mechanism which is accessible from
the bottom. To accommodate these checks, the breaker
should be turned on its right side resting on two-by-four wood
blocks. DO NOT use the portable breaker lift truck.
CAUTION: DO NOT REST UPON OR ALLOW ANYTHING TO
COME IN CONTACT WITH THE CLOSING SPRING
DISCHARGE ROLLER (item 4,Fig. 20) ON THE RIGHT SIDE
OF THE MECHANISM.
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1. 2X4 wood blocks
Figure 8 Breaker turned on right side
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8.5.1—Close Coil Plunger Gap
The close coil plunger gap and correct setting is shown in
Figure 9. The operation check and adjustment procedure for
the coil plunger will start with the close spring discharged,
and verification that the plunger moves freely over its full
stroke inside the coil. To check the closing coil plunger gap
the breaker should be open and the closing spring charged
and gagged. The measurement is made by first depressing
the close plunger button until resistance is felt, this accounts
for the free travel of the armature. The gap “T” measurement
is best made using a ‘go/no-go’ gauge. Refer to figure 9 for
gauge details. With the armature depressed until resistance is
felt the ‘go’ gauge must fit between the coil housing and the
surface of the black PVC cap covering the steel plunger base.
With the armature in the same position the ‘no-go’ gauge
must not fit between the coil housing and the plunger base.
The adjusting nut shown in Figure 9 is used to change this
measurement.
resistance is felt the “go” gauge must fit between the coil
housing and the surface of the red PVC cap covering the steel
plunger base. With the armature in the same position the “nogo” gauge must not fit between the coil housing and the
plunger base. The adjusting nut shown in Figure 10 is used to
change this measurement. The same procedure is used for
measurement and adjustment of trip coil #2.
ML-18 Breakers with type designation
-0, -1 & -2 T= 0.25” to 0.30”
ML-18 Breakers with type designation
-3. T= 0.35” to 0.40”
ML-18H Breakers with type designation
-0. T= 0.35” to 0.40”
Figure 9 Close coil plunger gap
8.5.2—Trip Coil Plunger Gap
The trip coils #1 and #2 plunger gap and correct setting is
shown in Figure 10. The operation check and adjustment
procedure for the coil plunger will start with the breaker in the
open position and the closing spring in the charged condition
and verification that the plunger moves freely over its full
stroke inside the coil. This verification is also required for the
second trip coil when supplied. To check the trip coil plunger
gap the breaker must be closed with the closing spring
discharged. The measurement is made by first depressing
the trip plunger button until resistance is felt, this accounts for
the free travel of the armature. The gap ‘T’ measurement is
best made using a ‘go/no-go’ gauge with the ‘go’ end having
a thickness of .200 inches and the ‘no-go’ end with a
thickness of .251 inches. With the armature depress until
Plunger Gap T =. 250+.000/-.050
Figure 10 Trip coil plunger gap
8.6—Control Switch Adjustment
Adjustment of various control switches is done as follows.
8.6.1 LCS and SM/LS Switch Adjustment
The breaker is to be in the open position with the opening and
closing spring discharged. This results in the control switch
plungers being in the depressed position. The switches to be
checked are shown in Figure 11. On the LCS and the SM/LS
&CHG switch, the plunger rod is to be flush or slightly
recessed (1/32”) within the rear of switch body. This is a
visual check.
8.6.2 CL/MS Switch Adjustment
The adjustment of the CL/MS on ML-18 models with type-3
designations and ML-18H models with Type-0 designation is
set at the factory and no adjustment is required. Replacement
of the CL/MS switch or removal of the angle mounting
bracket will require re-adjustment of this switch for correct
operation of breaker’s track interlock and close latch. The
adjustment will insure that the switch contacts will not close
before the close latch is in its re-set position. To achieve this
condition shims are required between the CL/MS switch
housing and the plunger spacer. Insert shims until the CL/MS
contacts do not close when the close latch is in the reset
position. Then remove .005inch shim to allow the switch
contacts to close just as the close latch reaches the re-set
position. This will provide the proper timing between the
CL/MS switch and the close latch.
The adjustment of the CL/MS on ML-18 models with type –0,
-1 and -2 designations is set at the factory. Should adjustment
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STACK SWITCH
BAR
IL/MS SWITCH
SHIM PLACEMENT
LCS SWITCH
be required, adjust the wiring terminals and set the plunger
dimension from .99 to 1.01 from its mounting bracket as
shown in Fig.11.
8.6.3 IL/MS Switch adjustment
The nut should be adjusted to fully extend the plunger.
AUXILIARY
SWITCH
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NEGATIVE
INTERLOCK
CLMS SWITCH
ML 18 TYPE –0, -1, & -2
CLMS SWITCH
ML 18 TYPE –3
ML 18 H TYPE -0
Figure 11 Control Switches
SECTION 9—Electrical Checks
Electrical checking consists of electrical breaker operation
primary and secondary wiring high-potential testing (if
required), primary circuit resistance (if required), PowerVac®
interrupter high-potential testing, and insulation resistance to
ground.
9.1—Electrical Operation
To check the electrical operation, attach a secondary test
coupler to the circuit breaker connector. Check the control
voltage on the nameplate and close and open the breaker
several times.
CAUTION: REPEATED OPERATIONS AT A RATE EXCEEDING TWO PER MINUTE MAY CAUSE CHARGING MOTOR
OVERHEATING AND FAILURE.
Leave the circuit breaker in an open and spring discharged
condition after checks are complete and refer to metalclad
instruction book GEK-39672 before inserting the circuit
breaker into a metalclad unit. Reinstall the front cover if it
has been removed.
9.2—High-Potential Test
If high potential tests to check the integrity of the primary
insulation is required, the AC high potential test described
below is strongly recommended. DC high potential testing is
not recommended. The following procedure must be adhered
to.
CAUTION: IF DC HIGH POTENTIAL TESTING IS REQUIRED,
THE DC HIGH POTENTIAL MACHINE MUST NOT PRODUCE
PEAK VOLTAGES EXCEEDING 50 kV.
NOTE: Always recheck with an AC tester if initial results are
questionable.
9.2.1 Primary Circuit
The breaker should be hipotted with the breaker closed.
An AC hipot machine capable of producing the test voltages
shown below may be used to hipot the breaker phase to
phase and phase to ground.
BREAKER VOLTAGE AC TEST VOLTAGE
4.16 KV 14 KV
7.2 KV 27 KV
13.8 KV 27 KV
The machine should be connected with its output potential at
zero and the voltage increased at 500 volts per second to the
test voltage and that voltage maintained for 60 seconds. The
voltage should then be returned to zero and the test leads
removed from the circuit and the breaker discharged to ground.
NOTE: Do not exceed the test voltage indicated for the
applicable breaker voltage rating. If the test should experience
a failure, STOP, turn off the test set and discharge the breaker
circuit.
1. Check the test set up and leads for connection errors.
2. Wipe down the breaker to remove any moisture, dust and
contamination.
3. Retest the breaker at the proper test voltage.
9.2.2 Secondary Circuit
Prior to hipotting the breaker secondary circuit, disconnect
the motor leads and thread a wire connecting all secondary
disconnect pins, except #24, the ground pin. Connect the
hipot machine from this wire to ground. Increase the voltage
to 1125 volts (rms) 60 Hz and maintain for 60 seconds.
Reduce the voltage to zero and remove the hipot machine
from the circuit. Remove the wire connecting the secondary
disconnect pins and reconnect the motor leads.
9.3—Primary Circuit Resistance
A resistance check of the primary circuit may be made
with the breaker closed. Use a low resistance measuring
instrument rated 100 amperes which measures in microhms.
The 100 ampere reading should be 30 to 60 microhms for a
1200 amp. Breaker, 25 to 50 for a 2000 ampere breaker. and
5 to 25 microhms for a 3000 ampere breaker when connected
across the primary bars on the breaker side of the disconnect
fingers. Do not connect directly to the disconnect fingers as
errors may occur due to finger spring pressure.
9.4—Vacuum Interrupter Integrity Test
NOTE: Use of a DC hipot is not recommended, but can be
used for quick field checks only. DC testers frequently yield
false negative test results due to the capacitive component of
the vacuum interrupter during DC testing. In addition, most
lightweight DC testers have a very low leakage current trip
setting. Always recheck with an AC tester if initial results are
questionable. Prior to performing any vacuum interrupter
integrity test, the outside (external surface) of the vacuum
interrupters should be wiped clean of any contaminates with a
non-linting cloth or industrial type wiper. This is critical: the
entire external surface is to be completely free of all dirt,
debris, dust, oil, etc.
CAUTION: X-RADIATION WILL BE PRODUCED IF AN
ABNORMALLY HIGH VOLTAGE IS APPLIED ACROSS A PAIR
OF ELECTRODES IN A VACUUM. X-RADIATION WILL
INCREASE AS VOLTAGE INCREASES AND/OR AS CONTACT
SEPARATION DECREASES. ONLY TEST A CORRECTLYADJUSTED CIRCUIT BREAKER.
DURING A HIGH POTENTIAL OR A VACUUM INTEGRITY
TEST, ANY X-RADIATION WHICH MAY BE PRODUCED WILL
NOT BE HAZARDOUS AT A DISTANCE SAFE FOR HIGH
POTENTIAL TESTING, IF THE TEST IS CONDUCTED AT THE
RECOMMENDED VOLTAGE AND WITH THE NORMAL OPEN
CIRCUIT BREAKER GAP.
DO NOT APPLY VOLTAGE THAT IS HIGHER THAN THE
RECOMMENDED VALUE. DO NOT USE CONTACT SEPARATION THAT IS LESS THAN THE RECOMMENDED OPENPOSITION BREAKER CONTACT GAP.
A vacuum integrity test of the interrupter is required to ensure
that no loss of vacuum has occurred. The vacuum integrity
test is performed using an AC hi-potential tester. This test of
the vacuum interrupter will determine its internal dielectric
condition and vacuum integrity. With the breaker open,
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