Yaskawa GA500 oC overcurrent on mixer start?
My Yaskawa GA500 VFD trips on an oC (Overcurrent) fault about two seconds after starting a mixer with a heavy load. The acceleration time is currently set to 3 seconds. What should I check?
The Yaskawa GA500 VFD tripping on oC (Overcurrent) during acceleration, especially with a heavy load, often indicates the acceleration time is too short for the load's inertia. It could also be due to the load being too heavy for the drive, or issues with the motor or its cabling. Check the acceleration time first, then verify the load and motor system.
Likely causes and checks
1Acceleration time too short for the load inertia
- Points to it
- The drive trips on oC (Overcurrent) during acceleration, specifically 'about two seconds after start' with an acceleration time of 3 seconds. This indicates the drive is struggling to accelerate the heavy load within the set time, drawing excessive current.
- Check
- Increase C1-01 (Acceleration Time 1) to a higher value (e.g., 5-10 seconds) and consider adjusting C2-01 to C2-04 (S-Curve Characteristics) to soften the ramp, then attempt to start the mixer. Monitor U2-05 (output current) at fault if it still trips.
2Load too heavy or drive undersized
- Points to it
- The problem description mentions a 'heavy load' on the mixer. If the load's current demand during acceleration exceeds the drive's capacity, it will trip on overcurrent.
- Check
- Measure the motor current during operation (if possible before the trip) and compare it against the drive's rated current and the motor's nameplate current. Also, verify the drive's maximum applicable motor output against the motor's rating.
3Motor cable short or ground, or damaged motor insulation
- Points to it
- While the trip occurs during acceleration, a motor or cable issue can cause overcurrent. An instant trip at start points to cable, motor or a coasting motor, but even an early ramp trip can be caused by these issues.
- Check
- Disconnect the motor at the drive terminals and perform an insulation resistance test (megger) on the motor and the motor cable. Measure cable-to-ground resistance.
4Run command while the motor is coasting
- Points to it
- If the mixer has significant inertia and is still spinning when a new run command is issued, the drive might experience an overcurrent as it tries to catch the spinning motor.
- Check
- Observe if the mixer motor is completely stopped before the run command is issued. If not, enable speed search at start by setting b3-01 = 1.
Next check: Start by increasing the acceleration time (C1-01) and adjusting S-curve characteristics (C2-01 to C2-04). If the issue persists, proceed to check the load, motor, and cabling.
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