Drives Service & Support
Fault Number : 5
Fault Display : OverVoltage
Fault Name : Overvoltage
Fault Type : 1 - Auto-Reset Run
Fault Description : DC Bus voltage exceeded the maximum value.
Corrective Action : This is a pretty comon fault. This fault can come from many different places at many different times. You need to find out when the fault actually occurs. Does it happen on power up, during deceleration or acceleration, during normal run, or while sitting idle. The voltage that the drive trips on is 285vac input (405vdc bus) at 200/240, 570vac input (810vdc bus) at 400/480, and 690vac input (975vdc bus) at 600V.
On Power up:
The first thing to check is the incoming line voltage. See the solution for sitting idle below. If the line voltage is known to be within specifications, then find the jumper used to ground the common mode capacitors. --Insert Picture-- (this is not on the frame A drive). This jumper removes the common mode capacitors from ground. An overvoltage may occur because of ground noise coming back in through these capacitors causing a rise on the DC bus. While this is uncommon, it is possible.
During Deceleration:
This is the most common time for an overvoltage to occur. This is caused by inertia from the load going faster than the commanded frequency. This happens during a ramp to stop action. When the load spins faster than the commanded frequency, the motor regenerates power back into the drive. A motor load turns into a generator. This power is fed back into the drive, and stored on the DC bus. Extending the time for deceleration is one way to solve an overvoltage during deceleration. A coast to stop will definitely solve the problem in this situation, but it is not always practical. If extending the decel time is not practical either, then a dynamic brake may be required to burn off the excess energy. A dynamic brake is a resistive device that removes energy from the bus and burns it off as heat. The only other solution is to reduce the inertia on the load to the motor. How you do that is dependant on your application. A constant overhauling load may be a good application for a regenerative drive, where instead of a dynamic brake removing energy by converting it to heat, a regen unit will put that energy back on the utility line, saving you money.
During Acceleration:
This is pretty uncommon, but it has been known to happen with very high interia loads with very long acceleration times. A flywheel is a common application with a high inertia. During acceleration, these loads can actually speed up quicker than the motor due to inertia, and the load becomes regenerative. To solve an overvoltage during acceleration, try to reduce the accel time by a little bit. This may take some trial and error to finally get to a proper accel time setting.
During normal running:
Check to see if the load on the motor has changed. If there are any clutches on the output load, that may be the cause. If there is a sudden drop in load, the motor may increase in speed quickly, causing a regenerative load. If this is the case, a dynamic brake may help absorb the energy. A dynamic brake is a resistive device that removes energy from the bus and burns it off as heat. Even with a high voltage line, and an application where a conveyor becomes less loaded may be enough to turn the motor into a regenerative load. The drive is usually able to absorb regenerative power to a certain extent, but too much will cause an overvoltage fault.
If the load is known to be stable, and not changing torque requirements drastically, then check the incoming line to the drive. See the solution for while the drive is sitting idle below.
Sitting Idle:
If an F05 happens while the drive is sitting idle, chances are there is a high incoming AC votlage line. If this is a sporadic fault, then there is something nearby that is causing the AC line to fluxuate. Investigate large induction loads to see if they are causing the distribution line to change voltage.
An improperly tapped transformer can also cause an overvoltage by keeping the incoming line at the high end of the recommended voltage. This will not allow much room on the DC bus for voltage changes if they were to occur. Fluxuations on the incoming line may not be detected by a multimeter. If it is a quick sharp rise in voltage, a multimeter may not be fast enough to capture the rise. An oscilloscope or Dranetz voltage monitor may be necessary to catch the rise in voltage.
Power factor correction caps switching in and out at the main incoming utility line may also cause a large spike on the power line. In this case, an isolation transformer or a line reactor may be necessary in front of the drive to absorb the spike in power.
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