Eaton Logo

How do I check the output of a drive with its output disconnected?

What a drive actually controls is the voltage and frequency on its output. It basically controls everything else by adjusting these 2 things. Checking the output voltage on the drive will indicate within a certain amount of reason that the drive is outputting what it should. To check this, do the following steps: 1. The drive must be set for ramp to start and not for flying start. Then, make sure everything is disconnected from the drive's output. This includes reactors, DV/DTs, etc. 2. With the drive powered up check for DCV from –DC bus to U, V & W. This voltage should be even and will probably be in the range of about 5VDC to 50VDC. If there is problems here it normally be either 0VDC or full DC bus. If either of these is seen the drive will have to be repaired or replaced. 3. Start the drive at 0 Hz or close to 0 Hz. Check from both the + & - DC bus to U, V & W. The reading should all be at about 50% of the full DC bus. Again if a problem is seen it will nor-mally show either 0VDC or full DC bus. If either of these is seen the drive will have to be re-paired or replaced. 4. Ramp the drive up to full speed and check U, V & W from phase to phase for ACV. The reading here may vary with the meter that is used so this measurement is more for reference, it will normally read high because of the PWM output. The readings should be even (the read-ings should be within a couple % of each other), if the readings are not within tolerance, re-pair or replace the drive. 5. Ramp the drive back down and turn off.