VFD DRIVES TROUBLESHOOTING

September 24, 2023

In this Article we are going to see VFD DRIVES TROUBLESHOOTING Common Fault Codes.

1.Drive does not start

Causes:

Drive not ready,
Drive not receiving a Run Signal,

Not Ready Causes:

Active fault,
DC bus too high or low,
Run enable input not present,

Run Signal not present:

Control place not correct Example trying to start from I/O when active control place is keypad.

2.Drive does not get to speed

Causes:

Missing reference,
Preset speed or jog speed active,

Missing Reference:

Check analog input monitor,
Check that the drive is programmed to follow the correct input,
Ensure the drive is not hitting any other limits,
Check frequency reference compared to output frequency,

3.Overcurrent

Causes:

Incorrect motor parameters,
Mechanical fault,
Electrical fault,
Current measurement error,

Solution:

Check wiring and motor for insulation failures and proper connections.
Check for mechanical overload, Locked rotor.
Check for proper drive size.

4.Current Limit Controller

Causes:

Incorrect motor parameters,
Mechanical fault,
Electrical fault,
Current measurement error,

Solution:

Not all models have an indication when the current limit is reached.
Current limit will reduce output frequency to reduce output current to at or below the current limit setting.

5.Ground Fault

Causes:

Faulty motor,
Electrical fault,
Current measurement error,

Solution:

Check for loose or high resistance connections to the motor.
Test motor for electrical failure.
Disconnect motor leads or apply known good motor to verify current measurements.

6.Output Phase Fault

Causes:

Loose Motor Connections,
Faulty Motor,
Current measurement error,

Solution:

Caused by current imbalance on the output of the VFD.
Look for loose connections or fault in motor winding's.

7.Overvoltage Fault

Causes:

High Line Voltage,
Regenerated voltage from load,
Excessive line side harmonics,

Solution:

If Fault occurs during deceleration or stop command, then increase deceleration time or brake chopper may be needed.
Cyclic loads may need regen unit or brake chopper.
Excess harmonics may be overcharging DC link capacitors.

8.Overvoltage Controller

Causes:

High Line Voltage,
Regenerated voltage from load,
Excessive line side harmonics,

Solution:

Trouble shooting is the same as for the overvoltage fault, the overvoltage controller will increase the reference in an attempt to bleed off excess voltage.
Not all series of VFD’s have an indication of when this controller is active.

9.Undervoltage Fault

Causes:

Low Line Voltage,
Improperly sized drive,

Solution:

Check for low line voltage or drops in line voltage under load.
Check for damaged input rectifiers with static checks.
Check for even current draw on input when drive is running.

10.Unit Over Temperature

Causes:

High Ambient temperature,
Insufficient airflow,
Plugged heat sink,
Failed cooling fan,

Solution:

Check Main cooling fan for rotation.
Ensure unobstructed heat sink and airflow.
Check ambient temperature is below the drives ratings.

11.Motor Over Temperature

Causes:

Overloaded Motor,
Operating Motor at high load at low speeds,
Undersized Motor,
Incorrect Motor Parameters,

Solution:

Check Motor Parameters.
Observe current and speed.
Current should be nearly proportional to speed, if running half speed at FLA drive will protect motor from increased thermal stress from reduced cooling.