FANUC Alarm SRVO-043 — SERVO DCAL alarm

Description

The energy produced by the regenerative discharge is excessive. As a result, all the generated energy cannot be dissipated as heat. When a robot is to be operated, a servo amplifier feeds energy to the robot. Along its vertical axis, however, the robot moves downward using potential energy. If the decrease in the potential energy exceeds the acceleration energy, the servo amplifier receives energy from the motor. This also occurs during deceleration even if the force of gravity has no effect. This energy is called regenerative energy. Normally, the servo amplifier dissipates this regenerative energy by converting it to heat. When the amount of regenerative energy exceeds the amount of energy that can be dissipated as heat, excess energy accumulates in the servo amplifier, thus triggering this alarm.

Remedy

When the LED indicator of the servo amplifier PSM displays '8' (DCOH alarm) (the DCOH alarm is issued when the thermostat detects overheating of the regenerative resistor): 1. This alarm might be raised when acceleration/deceleration is frequently performed or when a large amount of regenerative energy is generated in the vertical axis. In such cases, the robot should be used under less demanding conditions. 2. Check fuse FU1 on the servo amplifier. 3. Replace the regenerative resistor. 4. Check the cable between the servo amplifier (CRR45A) and the regenerative resistor. Replace it if necessary. 5. If this does not clear the alarm, verify that all connectors are securely connected.

Field diagnosis

The energy returned by the motors during braking or when a vertical axis descends exceeds what the discharge resistor can dissipate as heat.

What to check

• Reduce the duty: fewer back-to-back accelerations/decelerations, lower descent speed on loaded vertical axes.
• Check the discharge resistor fan and its cleanliness.
• If the code persists at a low cycle rate, the amplifier or its external resistor is at fault.
• Note: On heavy handling robots, it appears with the summer heat: the thermal margin of the resistor drops.

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