Rockwell-automation 1391ES AC Servo Controller User Manual download pdf (Page 23)

Description of Operation

Chapter 4

4-21

Fault Monitoring and Detection A number of Fault Monitor and Detection functions exist on the 1391B-ES

that guard the controller and help to minimize motor and system faults. The

occurrence of a fault will cause the controller to trip out. In this condition,

the Drive OK (DROK) contact will open and remain open until the fault is

cleared. If the DROK contact is wired into the user’s stop circuit, the

line/DB contactor (M) will also de-energize. This will place the shunt

resistor across the bus causing the motor to dynamic brake to a stop.

These fault conditions are annunciated through the front panel LED

indicators. The conditions displayed include:

Overtemperature

The controller contains a thermal switch on the heat sink which indirectly

senses transistor module temperature. If the temperature rating of the

switch is exceeded, the LED illuminates, the DROK contact opens and the

controller is disabled.

Power Fault

A fault related to the power bridge section of the controller will cause the

controller to be disabled, illuminate the LED and open the DROK contact.

Control (Power) Fault

If the control voltage varies more than ±10% of the nominal 12V DC or the

resolver wiring is grounded or missing, this fault will occur. When a fault

is detected, the LED illuminates, the DROK contact opens and the

controller is disabled.

Overvoltage

The DC power bus voltage is continuously monitored. If it exceeds a preset

level of 405V DC, the LED illuminates, the DROK contact opens and the

controller is disabled

Undervoltage

If the DC power bus voltage drops below 50% of its nominal operating

value, the LED illuminates and a signal will be present at TB2-13. A

switch setting on S2 selects the reaction of the DROK contacts to an

undervoltage detection. Two options are possible: 1) DROK opens, but

closes when the bus voltage is restored; 2) DROK is not affected by an

undervoltage.

Important: Regardless of interaction with the DROK contacts, the

transistor bridge is disabled upon an undervoltage condition. This is done

to protect the output transistors against voltage transients.

Current Foldback

The controller contains a fixed time versus current overload circuit which

monitors the current through each leg of the output bridge. If a fixed-time

versus current-product is exceeded, the LED is illuminated and a signal

will be present at TB2-14. This condition will reduce the current limit or

torque available to the motor.

Run/ Enable

The application of an enable signal by the machine position controller will

cause the RUN ENABLE LED to illuminate.

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Rockwell-automation 1391ES AC Servo Controller User Manual Page 23

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