Yaskawa Sigma-7 A.400 trips on deceleration, what to check?
My Yaskawa Sigma-7 SERVOPACK is throwing an A.400 alarm, but only when the machine decelerates. It's a heavy load, and the stops are pretty fast. What should I be looking at first?
An A.400 Overvoltage alarm on a Yaskawa Sigma-7 SERVOPACK indicates that the main circuit DC voltage is too high. If this alarm specifically occurs during deceleration, it points to issues related to regenerated energy. This can be caused by an unsuitable regenerative resistor, an excessive moment of inertia ratio, or a disconnected regenerative resistor.
Likely causes and checks
1External regenerative resistance too high for operating conditions
- Points to it
- During deceleration of a high-inertia load, the motor acts as a generator, feeding energy back into the SERVOPACK. If the external regenerative resistor's value is too high, it cannot dissipate this regenerated energy effectively, leading to a DC bus overvoltage.
- Check
- Check the operating conditions against the regenerative resistance and select a suitable value. Ensure the resistor is correctly sized for the application's deceleration requirements.
2Moment of inertia ratio or mass ratio above allowable value
- Points to it
- A high moment of inertia ratio or mass ratio, especially with fast deceleration times, generates a significant amount of regenerative energy. If this energy exceeds the system's capacity to dissipate it, an overvoltage alarm will occur.
- Check
- Verify that the moment of inertia ratio is within the allowable range for the SERVOPACK and motor. Consider increasing the deceleration time or reducing the load to lessen the regenerated energy.
3Regenerative resistor disconnected
- Points to it
- If the regenerative resistor is disconnected, there is no path for the regenerated energy to dissipate during deceleration. This will cause the main circuit DC voltage to rise rapidly, triggering the A.400 alarm.
- Check
- Measure the regenerative resistor to check for an open circuit. If it's an external resistor, replace it. If the built-in resistor has failed, the SERVOPACK may need replacement.
Next check: Since the alarm specifically occurs during deceleration, first verify the external regenerative resistance value against the operating conditions. Then, check the moment of inertia ratio and deceleration time settings. Finally, inspect the regenerative resistor for continuity.
Related questions
Describe the fault or upload a photo, and InduQT checks it against the manufacturer manuals. Share the result here when it helps someone else.