Installation & Operating Procedures
Opal OP-STOP
Series
DC INJECTION BRAKE
FOR 3 PHASE INDUCTION MOTORS
OP-STOP DC INJECTION BRAKE
Opal OP-Stop SERIES
DC INJECTION BRAKE
FOR 3 PHASE INDUCTION MOTORS
INSTALLATION & OPERATING PROCEDURE
Revision 1.03 - 07/2011
OP-STOP DC INJECTION BRAKE
FOR YOUR SAFETY
Only qualified personnel should install this equipment, after first reading and
understanding all the information in this manual. All instructions should be strictly
adhered to. The user should consult SAF Drives Inc. or a SAF OPAL Starters
supplier for clarification of the contents of this manual should any doubt or
questions arise.
The installation of this equipment must be conducted in accordance with all
national, regional and local electrical codes.
All drawings and technical representations included in this manual are for typical
installations and should not in any way be considered for specific applications or
modifications. Consult SAF OPAL Starters for supplemental instructions.
SAF Drives Inc. accepts no liability for any consequences resulting from
inappropriate, negligent or incorrect installation, application or adjustment of this
equipment.
The contents of this manual are believed to be correct at the time of printing. In
following with our commitment to the ongoing development and improvement of
our products SAF OPAL Starters reserves the right to change the specification of
this product and/or the content of this instruction manual without notice.
OP-STOP DC INJECTION BRAKE
TABLE OF CONTENTS
1 DESCRIPTION..............................................................................................................1
1.1 OVERVIEW........................................................................................................................1
1.2 APPLICATION NOTES......................................................................................................2
1.3 CONTROLS....................................................................................................................... 3
1.3.1 CA398 LOGIC................................................................................................................3
1.3.2 CA398 REGULATION....................................................................................................3
2 SPECIFICATIONS ........................................................................................................4
2.1 POWER RATING...............................................................................................................4
2.2 CURRENT AND FUSE RATING........................................................................................4
2.2.1 NOTES...........................................................................................................................4
2.3 SERVICE CONDITIONS....................................................................................................5
2.4 DIMENSIONS ....................................................................................................................5
2.5 SCR INSTALLATION SPECIFICATIONS..........................................................................6
3 CARD FUNCTIONS ......................................................................................................7
3.1 CARD LAYOUT .................................................................................................................7
3.2 LED AND NEON INDICATIONS........................................................................................7
3.3 ADJUSTMENTS ................................................................................................................8
3.3.1 POTENTIOMETERS......................................................................................................8
3.3.2 1LINK SELECTION........................................................................................................8
3.3.3 PUSHBUTTON ..............................................................................................................8
3.4 TERMINALS ......................................................................................................................9
3.4.1 CUSTOMER TERMINALS.............................................................................................9
3.4.2 TERMINALS FOR INTERNAL USE...............................................................................9
3.5 FAULTS...........................................................................................................................10
3.5.1 PHASE LOSS ..............................................................................................................10
3.5.2 INSTANTANEOUS OVER CURRENT (IOC)...............................................................10
4 INSTALLATION AND START UP............................................................................... 11
4.1 INSPECTION...................................................................................................................11
4.2 SAFETY PRECAUTIONS................................................................................................11
4.3 MOUNTING GUIDELINES...............................................................................................11
4.4 WIRING GUIDELINES.....................................................................................................13
4.5 START UP.......................................................................................................................13
4.5.1 CHECKS BEFORE POWER-UP..................................................................................13
4.5.2 WITH POWER ON.......................................................................................................14
5 TYPICAL CONNECTIONS..........................................................................................15
5.1 STAND ALONE DC INJECTION UNIT WITH ZERO SPEED DISABLE..........................15
5.2 OPAL STARTER WITH DC INJECTION .........................................................................16
5.3 REVERSING OPAL STARTER WITH DC INJECTION, 125 AMPS AND BELOW..........17
5.4 REVERSING OPAL STARTER WITH DC INJECTION, 200 AMPS AND ABOVE..........18
6 SPARE PARTS...........................................................................................................19
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OP-STOP DC INJECTION BRAKE
1 DESCRIPTION
1.1 OVERVIEW
The OP-STOP braking units provide smooth braking for AC induction motors. The brake units
offer adjustable braking because they are current controlled. Unlike a mechanical brake, an
electrical brake will never wear out. The brake operates by injecting DC current in two phases
of the motor to rapidly decelerate it to zero speed.
These units can be supplied as an option to the OPAL solid state starter, or as stand alone units
for new or retrofit installations.
SAF's OP-STOP braking modules offer a unique combination of features that make it very
reliable, easy to use, and energy efficient. These features include:
• Closed Loop Current Regulation:
The brake, operating with a closed loop current regulator, provides consistent torque
every time. This torque is independent of line voltage variations.
• Direct Power Connection:
The brake's power input is connected directly to the AC line, and the power output is
connected directly to the motor, no contactors are required. The unit adapts itself to any
input voltage between 200 and 600 VAC with no adjustments required.
• Efficient Power Circuit:
The power circuit is an efficient four Silicon Controlled Rectifier ( SCR ) configuration
which uses some of the SCR's as a "free wheeling diode", thus maximizing the DC
current through the motor coils generated by the AC input current.
With every benefit there is usually a trade-off. Although the OP-STOP brake unit will never
wear out like a mechanical brake, the trade-off is that should there be a loss of power, the brake
unit will not operate without battery back-up. SAF can supply a reliable battery back-up to
overcome this disadvantage.
Braking is initiated when the motor starter is opened and the voltage across the motor has
dropped to below 30% or 80% of the line supply. DC injection is removed after an adjustable
period has elapsed. It does not provide zero speed sensing, although a normally closed contact
from a zero speed switch may be connected to the Disable Input.
If braking is released before the motor stops, the motor will coast to rest. If the braking remains
on after the motor stops, the DC supply will provide a holding brake.
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OP-STOP DC INJECTION BRAKE
1.2 APPLICATION NOTES
The motor torque/speed characteristic of an induction motor under DC supply is similar to the
normal curve published for constant frequency, at 50 or 60 Hz, but this time having
"synchronous speed" zero RPM. This is illustrated below.
ORQUE
SPEED
S 100%
0=N
For smooth braking the DC current is typically adjusted to 300% of the motor nameplate
current. The stopping time depends on the torque setting and also the inertia of the mechanical
system.
Electric braking is not recommended for continuous or repetitive operation. The kinetic energy
of the mechanical system is transformed into heat during braking ( energy conservation ). That
heat is dissipated in the rotor of the motor.
On wound rotor motors the external rotor resistance will absorb most of the energy. On squirrel
cage motors, overheating of the motor is a real danger if frequent operation is used.
Keeping DC current on the motor stator for a short time after the motor has stopped is quite
acceptable. The heat produced by the I2R losses are not significant, and they are dissipated in
the stator only, not in the rotor where the rotational energy is dissipated.
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OP-STOP DC INJECTION BRAKE
1.3 CONTROLS
The OP-STOP unit contains two major parts, the power circuit and the control card.
The power circuit is a 4 SCR single phase full wave controlled rectifier. This configuration
optimizes the DC current injected to the motor per input current.
The control is contained in a single PC board, CA398. This board is common to all OP-STOP
models.
1.3.1 CA398 LOGIC
DC injection will be applied to the motor when two conditions are met. The starter is
opened and the motor terminal voltage has decayed to 30% or 80%, jumper dependent, of
the line voltage. The starter can not be energized for a period of 1-2 seconds after the DC
injection cycle.
This design has the significant advantage that the braking module will remain off in the
case of having an open auxiliary contact from either a broken wire or faulty contact. The
braking action can be externally defeated at any time by applying 115 VAC to the
Disable Input.
The braking action is inhibited when an instantaneous over current is detected. The IOC
fault is detected and latched until the Reset switch is pressed. A form C relay contact is
available to interlock the brake unit from the motor starter. The starter cannot be
energized while DC current is being applied to the motor or during a fault condition.
1.3.2 CA398 REGULATION
The brake module operates in current control at all times. The current is adjusted via an
internal potentiometer and the current feedback signal is generated by a current
transformer mounted on the AC line. A unique circuitry reconstructs the free wheeling
current in the DC output for accurate current regulation.
The output of the current regulator is used in a comparator circuit that performs the phase
control on two SCR's. The other two SCR's are fully phased on to provide free wheeling
action, minimizing the ripple current.
Two opto-couplers are used to generate the line synchronization signal. Each opto output
is used to generate a ramp that is used in the comparator with the current regulator
output.
The motor voltage feedback is used to sense voltage levels for proper sequencing and not
to perform any regulation.
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