Rockwell Automation 1398-DDM-xxx ULTRA 100 Series Drives Installation Manual - Manual (Page 109)

Publication 1398-5.2 – PDF 1997
Power Connections 7-5
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within 20 seconds at 600% overload
Power Supply Protection
The feedback encoder, auxiliary encoder and optional TouchPad are
powered by a single internal power supply. The power supply has a
“resettable” fuse that opens at 3 amps and automatically resets itself
when the current falls below 3 amps.There are no internal fuses
requiring replacement.
Emergency Stop Wiring
An overlapping contactor may be inserted between the motor and the
drive for emergency stop purposes. The contactor must not simply
break the motor current, it also must switch a three phase resistive
load in parallel with the motor windings.
The three resistors provide dynamic braking. In addition, they prevent
continuous arcing at the main contacts when breaking DC currents,
such as when the motor stalls. Simply breaking the motor current can
result in high voltages due to motor inductance, which will cause
prolonged arcing in the contactor. In extreme cases, the prolonged
arcing could result in the contactor catching fire. An overlapping
contactor provides the required timing by engaging the braking
contactors before the drive contactors disengage.
Figure 7.3 depicts a contactor installation with resistive loads.
Guidelines for the installation include:
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Resistor values should be one to four times the winding resistance
for good braking performance. Refer to Appendix F, “Dynamic
Braking Resistor Selection” for resistor sizing equations.
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Screen and ground cables should be connected as shown.
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Shields should be unbraided (not a drain wire soldered to the
shield).
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Connection lengths should be minimized.
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Safety ground (GND) and shield connections are permanently
connected. This is essential for electrical safety.
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EMC guidelines require connection of the shield at the point
where the contactor is inserted.