Ultra Start 450 SERIES Installation Manual download pdf (Page 109)

Publication 1398-5.2 – PDF 1997

Power Connections 7-5

● within 20 seconds at 600% overload

Power Supply Protection

The feedback encoder, auxiliary encoder and optional TouchPad are

“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:

● 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.

● Screen and ground cables should be connected as shown.

● Shields should be unbraided (not a drain wire soldered to the

shield).

● Connection lengths should be minimized.

● Safety ground (GND) and shield connections are permanently

connected. This is essential for electrical safety.

● EMC guidelines require connection of the shield at the point

where the contactor is inserted.

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Ultra Start 450 SERIES Installation Manual Page 109