Benshaw DCB3 User Manual

890013-01-05

DCB3 SERIES
INSTRUCTION MANUAL

INDEX

TITLE PAGE

PRE-START-UP INSPECTION 2

GENERAL 2

POWER ASSEMBLY TECHNICAL DATA 2

OPTIONS 3

ZERO SPEED RELAY CONTACTS 3

CONNECTION PROCEDURES FOR 4

DC INJECTION BRAKING

USING POWER FACTOR CAPACITORS 6

INDUCTION MOTOR TEMPERATURE MEASUREMENT 6

PREVENTATIVE MAINTENANCE 6

SPARE PARTS 7

TROUBLESHOOTING 8

1

DCB3 SERIES
INSTRUCTION MANUAL

PRE-START-UP INSPECTION

1. Clean out all metallic particles and foreign matter.

2. Check all connections for tightness. Use recommended procedure for aluminum conductors.

3. On high resistance ohmmeter scale check L1 to T1, T2. Repeat for L 2. Check all terminals
to ground. All readings should be several megohms or more.

GENERAL

Benshaw DCB3 DC Injection Brakes are used to provide DC braking current for induction type AC motors while operating in
conjunction with an external motor starter that has its own start/stop control. When the external motor starter removes power
from the motor, the loss of AC voltage at the motor leads triggers the D.C. brake.

When activated, the brake provides an adjustable DC current to two leads of the motor (0-300% full load amperes (FLA) STD
Duty, 0-500% heavy duty) which develops braking torque. This current is applied for a time period adjustable from one and
one-half to thirty seconds. A normally closed brake aux contact is provided to prevent restarting of the motor while brake
current is applied. The voltage on the third lead of the motor is sensed to detect when the motor reaches zero speed, turning
off the D.C. brake and allowing the motor to be restarted. A "Time" adjustment limits the maximum time that the D.C. brake
can be on. The stopping brake torque adjustment enables smooth motor deceleration to zero speed providing controlled
stopping times. This adjustment procedure reduces hazards associated with coasting machinery, overhauling loads, etc.

Three sets of Form C contacts are provided for external use, one set signals operation of the brake, and the other two can
indicate when the motor reaches zero speed. Optional features include an input for zero-speed sensing by a proximity switch,
and two dry contact inputs; one for independent brake operation (useful for "anti-windmilling" on large fans, for example) and
another to inhibit D.C. brake operation when desired. The PC board can also be modified to extend the max. brake time from
30 sec. to one minute.

POWER ASSEMBLY TECHNICAL DATA

Each DCB3 Brake contains SCRs which have a minimum peak inverse voltage (PIV) rating of two and one-half times the
line-to-line AC voltage and a root mean square (RMS) current rating normally selected to be three times the full load
continuous current to the motor.

DCB3 Brakes are rated to operate at the maximum DC current with a maximum ambient temperature of 40° C at an altitude of
6,500 feet (2,000 meters) above sea level. Derating of one and one-half percent per degree C above 40° C and one percent
for every 330 feet (100 meters) above 3,300 feet, must be considered when applying DCB3 Brakes.

2

DCB3 SERIES
INSTRUCTION MANUAL

OPTIONS

The P.C. board for the DCB3 can be modified to add the following options:

1. Extended brake Time – The standard range for adjusting the max. brake time is from 1.5 to 30 seconds. If desired, this
range can be doubled to go from 3 seconds to one minute. Doing so, however, could damage the motor if high levels of
brake current are applied for extended periods.

2. Prox switch sensing of motor speed – Normally the DCB3 senses when the motor comes to stop by monitoring the
voltage present at the motor leads. When the motor stops, the DCB3 stops applying brake current to the motor and then
allows it to be restarted. If it is desired to conclude braking when the motor slows to a desired speed instead, the card can
be modified to sense “Zero Speed” by monitoring a prox switch that is placed to sense motor rotation. The card is
modified by cutting the P.C. trace under Link 1 and installing Link 2. When the frequency at the switch input drops
below a set level, the DCB3 stops applying brake current to the motor and allows it to restart. The “PROX SW” pot on
the card sets this level from 0.8 Hz. (suitable for a switch sensing one pulse per revolution), to 40 Hz. (suitable for a
switch sensing gear teeth).

A DC type of prox switch is needed – Approximately 30 volts DC is available for powering the switch at TB1-6 (“+”)
and TB1-13(“-“). The switch output (connected to TB1-12) can be an open collector type with either NPN or PNP
polarity, or it can have a bipolar output. The output signal should be a square wave or pulse train at least 8 volts p-p.

ZERO SPEED RELAY CONTACTS

The PC board is supplied with a six-position terminal block connected to a relay that is energized whenever the “ZERO
SPEED” LED is lit. The contacts are two sets of “Form C” contacts. The first set has its normally open contact connected to
TB5-1, its common contact to TB5-2, and its normally closed contact to TB5-3. Similarly, the second set is connected with
its normally open contact at TB5-4, its common contact at TB5-5, and its normally closed contact at TB5-6. This relay
energizes when power is first applied. It drops out when the motor is started, it stays out when the motor power is removed
and during braking, and it energizes when the motor stops or the brake time is over. Since the zero speed sensing circuit
needs voltage at the motor to detect rotation, the motor may still be turning when the relay is energized if the brake current
stops while the motor is still turning. Because the prox switch option makes the “Zero Speed” LED pulse with each switch
transition as the motor comes to a stop, the contacts will chatter. Therfore, these two features should not be used together.

3

DCB3 SERIES
INSTRUCTION MANUAL

CONNECTION PROCEDURES FOR

DC INJECTION BRAKING

WARNING !

Equipment is at line voltage when AC power is connected. Pressing "STOP" push-button does not remove AC mains
potential. All phases must be disconnected before it is safe to touch motor terminals or control equipment parts.

REMOVE AC POWER

1. Connect two phases of the power input from the motor starter to terminals L1 and L2. Wire should be sized according to
the motor current. Wire sizing may be determined by consulting local and/or NEC recommendations.

2. Connect three phases of the starter output to the motor to terminals T1, T2 and T3. Be sure they are connected between
the motor overload and the motor. T1 should be on the same phase as L1, and T2 should be on the same phase as L2.

3. Open the control connection to the coil of the motor starter and connect DC brake terminals 7 and 8 in series with the
coil of the motor starter.

4. It may be desired for motor protection, that the starter overload, if tripped, should inhibit the DC brake. To do this, a set
of N/O overload contacts should be connected to terminals 16 and 17 on the DC brake PC board. If the overload does
not have a set of N/O contacts available, use a pilot relay circuit.

5. If desired, the optional dry contact inputs for independent brake and/or brake inhibit 5 can be connected. Connecting a
normally-open contact to terminals 14 and 15 will allow independent D.C. brake operation whenever the motor isn't
running and the contact is closed. Connecting a normally-open dry contact to terminals 16 and 17 will allow braking to
be inhibited whenever the contact is closed. NOTE these inputs are for dry contact connection only. Do not connect any
control voltages, either AC or DC, to these inputs or erratic operation and equipment damage could result.

6. The DC current through the motor must be measured to properly adjust its level. Temporarily install a DC ammeter in
series with the brakes T1 lead with the "+" side away from the DCB3 Brake. The DC ammeter must be capable of
reading at least 300% (500% Heavy Duty) of the motors full load ampere (FLA) rating.

4

DCB3 SERIES
INSTRUCTION MANUAL

7. On the DCB3 card in the DC brake, turn potentiometers "TORQUE" and "TIME" fully counterclockwise (CCW). Turn
the "ZERO SPEED SENS" potentiometer fully clockwise (CW).

*Adjustments: Zero Speed Sensing: max to min.

Torque: 0% to 50% rated motor torque (0% to 300% FLA DC current)
0 to 130% rated motor torque (0-500% FLA DC Current Heavy Duty)
Time: 2 seconds to 30 seconds
Aux Switch: 0.8HZ to 40HZ

8. Apply AC power to the combination of the motor starter and the DC Brake.

9. Energize the motor starter. The "RUNNING" LED on the DCB3 card should be lit. Verify that the motor comes up-to­speed.

10. De-energize the motor starter. On the DCB3 card, the "Running" LED should turn off and the "Brake" LED should come
on. The "Brake" LED should go out approximately 1.5 seconds after it comes on.

11. Calculate the maximum recommended braking current by the following formula.

Maximum Braking Current (DC) = 3 x Motor FLA (AC)

5 x Motor FLA (AC) Heavy Duty

12. On the DCB3 card, turn the "TIME" potentiometer fully clockwise (CW). Start the motor and allow it to come up-to­speed. Stop the motor. The "BRK ON" LED should turn on. Gradually turn the "BRK TORQUE" potentiometer, CW,
until the DC ammeter indicates the desired - maximum - recommended braking current.

13. Check the time required for the motor to stop. If the motor stops too quickly, the "TORQUE" potentiometer can be
turned CCW for the desired stopping time (this will vary for each application and will have to be adjusted accordingly).
DO NOT, in any case, exceed the maximum recommended braking current. (Reference No. 11., above).

14. The "TIME" potentiometer should be adjusted so that the "Brake" LED goes out a few seconds after the motor stops.
Turning the pot CCW reduces the time. Allow sufficient time for motor cooling between successive stops.

15. Once the "TORQUE" pot has been adjusted, the "ZERO SPEED SENS" pot can be adjusted. With the motor stopped,
temporarily jumper terminals 14 and 15. The "BRAKE" LED should come on, and the DC ammeter should register
brake current. Gradually turn the "ZERO SPEED SENS" pot CCW until the "ZERO SPEED" LED comes on. Turn the
"ZERO SPEED SENS" pot slightly further CCW and remove the connection.

16. Disconnect power. Remove the DC ammeter and reconnect the wiring. The unit is now ready for use.

5

DCB3 SERIES
INSTRUCTION MANUAL

WARNING !

Equipment is at line voltage when AC power is connected . Pressing "STOP" push-button does not remove AC mains
potential. All phases must be disconnected before it is safe to touch motor terminals or control equipment parts.

REMOVE AC POWER

USING POWER FACTOR CAPACITORS

Power factor correction capacitors can be used in conjunction with the DCB3 Brake; however, the capacitors must be added
ahead of the brake and never between the brake and the motor. If the capacitors are installed between the brake and the
motor, serious damage to the brake and/or the motor may result.

INDUCTION MOTOR TEMPERATURE MEASUREMENT

The motor's stator winding temperature rise can be determined by recording the winding resistance at room temperature
before operation and after the motor has reached running temperature at full load. Using a digital ohmmeter capable of
reading milliohms, calculate the stator winding temperature rise by using the following formula:

Temperature Rise: T= (RF/R)-1) (234.5 + t) (Degrees C)
RF = Resistance in ohms of final temperature measurement
R = Resistance at beginning of test
t = Room temperature at beginning of test

PREVENTATIVE MAINTENANCE

The components of the DCB3 Brake will not deteriorate with use; however, some routine inspection and maintenance is
suggested. Periodically disconnect brake input power and vacuum or blow off accumulated debris on the internal parts with a
high-velocity, low pressure blower.

Power connections on newly installed brakes may relax and loosen after two or three weeks of operation. Turn power off and
retighten. Check annually thereafter; more often if vibration is present. Loose power connections can cause voltage spikes,
overheating, malfunctioning, or failure.

6

DCB3 SERIES
INSTRUCTION MANUAL

SPARE PARTS

HP @ 480V DESCRIPTION

PC CARD BIPC-300020-XX BIPC-300020-XX 1

5-15 SCR BISCR5012X BISCR5012X 3

20 SCR BISCR5012X BISCR5012X 3
30 SCR BISCR5012X BISCR10012X 3
40 SCR BISCR10012X BISCR13212X 3
50 SCR BISCR10012X BISCR13212X 3
60 SCR BISCR13212X BISCR16212X 3

75 SCR BISCR16112X BISCR21012X 3
100 SCR BISCR21012X BISCR66012X 3
125 SCR BISCR25012X BISCR6601218 3
150 SCR BISCR6601218 BISCR6601218 3
200 SCR BISCR6601218 BISCR15001850 3
250 SCR BISCR6601218 BISCR15001850 3
300 SCR BISCR8801830 BISCR15001850 3
400 SCR BISCR15001850 3
500 SCR BISCR15001850 3
600 SCR BISCR15001850 3
700 SCR

Based on HP @ 480V
**4 = 480V

PART NUMBER

STANDARD DUTY

PART NUMBER

HEAVY DUTY QUANTITY

For other voltages, calculate as follows 480 .

Operating Voltage x Motor HP = Brake size (rated at 480V)

or

HP @ 230V, take HP x 2.4 = FLA FLA divided by 1.2 = HP @ 480V
HP @ 208V, take HP x 2.7 = FLA FLA divided by 1.2 = HP @ 480V
HP @ 380V, take HP x 1.52 = FLA FLA divided by 1.2 = HP @ 480V
HP @ 575V, take HP x .96 = FLA FLA divided by 1.2 = HP @ 480V

7

DCB3 SERIES
INSTRUCTION MANUAL

TROUBLE SHOOTING

PROBLEM POSSIBLE CAUSE AREA OF CORRECTION

Motor continues to coast
even though "BRAKE" LED
is on and TORQUE" pot is
turned up.

LED's don't light up and unit
won't work.

1. Blown fuse(s).

2. Gate connections open
on SCR's.

1. Motor operating voltage
not present on Terminals 1
and 2 on P.C. board.

2. Defective P.C. board.

3. Blown fuse on card.

1. Replace fuse (always check SCRs
for shorts after changing fuse)

2. Check for 8-200 ohms from G to K
terminals on PC board. If bad, check
wiring to SCR's

1. Check voltage at P.C. board
Terminals 1 & 2.

2. Replace P.C. board.

3. Replace fuse.

8

Revision History;

Revision Date ECO#

03 8/24/01 118

04 10/10/ 01 201
05 12/10/ 02 -

BENSHAW PRODUCTS

Low Voltage Solid State Reduced Voltage Starters

RSD/RSM6 - SSRV Non or Separate Bypass

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RDB/RMB6 - SSRV Integral Bypass

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RSM7 - SSRV + DC Injection Braking

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RSM10 - SSRV + Reversing

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RSM11 - SSRV + DC Injection Braking + Reversing

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RSM10/12TS - SSRV Two Speed

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WRSM6 - SSRV Wound Rotor

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SMRSM6 - SSRV Synchronous

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DCB3 - Solid State DC Injection Braking

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Medium Voltage Solid State Reduced Voltage Starters

5kV - Induction or Synchronous to 10,000HP

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15kV - Induction or Synchronous to 60,000HP

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