# Powerflex 753 "Clogging" Motor & Transistor Over Temp



## gpop (May 14, 2018)

do you have a contactor, disconnect or anything between the vfd and motor. Is it possible that you are dropping a leg (powerflex by default will not trip on motor phase loss you have to program that)


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## gpop (May 14, 2018)

Someone link this to Jreaf as i can not figure out how to do it.


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## Forge Boyz (Nov 7, 2014)

@JRaef 

Sent from my SM-G970U using Tapatalk


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## Almost Retired (Sep 14, 2021)

gpop said:


> do you have a contactor, disconnect or anything between the vfd and motor. Is it possible that you are dropping a leg (powerflex by default will not trip on motor phase loss you have to program that)


i agree with gpop ,. strong possibility you have lost a phase somewhere


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## Forge Boyz (Nov 7, 2014)

gpop said:


> Someone link this to Jreaf as i can not figure out how to do it.


Type in the @ symbol, and you will get a pop up where you type in the username of the person you want to mention. When you find it, click on their username and it will be automatically linked in the text.

Sent from my SM-G970U using Tapatalk


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## Keepin R' Wet (5 mo ago)

There is no contactor. Power fed goes from the MCC w/ a 350A fuses which have all been checked to the VFD which the input was checked as well 485VAC P-P and 278 P-G w/ 675DC at the VFD bus. From the VFD it goes to a Load Reactor and then Straight to the Reuland 175HP motor. I used a DLRO to test connection points for a loose connection but all were tight and sound per the meter device. The VFD isn't losing a phase since I did test the drive against a small motor and it worked perfect. The only thing I have not done was run a temporary cable from the load reactor to the motor however the megger test showed the conductors were >4000MΩ. I agree it is acting like it single phasing however it is not as voltages/current between phases are balanced.


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## Almost Retired (Sep 14, 2021)

so amps are balanced, are they the amount you expected ?
have you checked amps on each phase into the drive while attempting to run ?
since it will run a 15HP but not a 175HP
it generally sounds like a lack of power

the term is cogging ... not clogging
as in the cogs on a gear
cogging is what usually happens when a DC motor is asked to turn too slow
it is the result of the brushes moving from one commutator bar to the next


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## Keepin R' Wet (5 mo ago)

Almost Retired said:


> so amps are balanced, are they the amount you expected ?
> have you checked amps on each phase into the drive while attempting to run ?
> since it will run a 15HP but not a 175HP
> it generally sounds like a lack of power
> ...


Yes you are correct, cogging not clogging. That was a typo on my part. I'll be honest I have not checked the amperage on the input side which I can do on our next starting test. Now the "cogging" is only when we have forward rotation which can only be achieved after changed control from V/Hz to Induction SV (sensor less vector) and followed up w/ a auto tune. When the motor drives forward it is very twitchy and doesn't look good at all. This is happening w/ a command speed of 800RPM and the currents we are seeing is between 250-325A which we do not expect w/ a un-coupled motor. Now, the drive will only move forward (CW) only once after the auto tune, after that it'll start acting like is was doing before which is slightly move in the CCW position then move about 1/4 of a turn in the CW position then free wheel in the CCW position. This is a typical time when we get the high currents. Sometimes the shaft won't turn at all, sometimes the shaft will appear it wants to drive forward w/ some slight twitching and then kick back in the CCW rotation a 1/4-1/2 a turn. It's pretty much inconsistant however I do know that when the motor does move into the CW position that we get the high currents but regardless what the drive does we get the Fault 9 (Transistor Over Temp) after each attempt to jog the uncoupled motor.


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## Keepin R' Wet (5 mo ago)

Just to be clearer here, the twitchy rotation is only when we change the drive to SV w/ the auto tune and we do get twitchy rotations w/ NO F9 Transistor Over Temp. Only after that one jog attempt it will result in getting the F9 faults and only move forward 1/4 of a turn.


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## Almost Retired (Sep 14, 2021)

transistor over temp could easily be the result of the high output current

bottom line if it used to work just fine, and then suddenly quit .....
something broke
ya gotta find it !!!
somewhere somehow, keep checking every tiny little thing
and dont forget .... somebody may have monkeyed with the drive and isnt telling on themselves
if you havent already double check the parameters
you may even need to do a hard reset to factory default and start over

there are things so far back in the menu, that most ppl dont even look at them


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## gpop (May 14, 2018)

Bypass the load reactor then either run V/H or autotune again before testing.


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## Keepin R' Wet (5 mo ago)

gpop said:


> Bypass the load reactor then either run V/H or autotune again before testing.


Did do that, same result


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## gpop (May 14, 2018)

Did you copy the program using the him. If so consider factory reset the reprogram.

Also check speed command parameter to see what the drive thinks it's doing. I have seen a rogue 1 in bit 15 of the code keep rapidly changing the speed from plus to minus ( you can program the analog input to fault if it goes negative or drops below 3.5ma)


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## just the cowboy (Sep 4, 2013)

What type of SV setup did you do, Static or rotary?
Static will just bump the shaft like you describe, rotary will run it up to speed.
I would look at the incoming voltage, unless disabled you can run a drive with single phase in but it will only run a load at less than half the rated hp.


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## Keepin R' Wet (5 mo ago)

gpop said:


> Did you copy the program using the him. If so consider factory reset the reprogram.
> 
> Also check speed command parameter to see what the drive thinks it's doing. I have seen a rogue 1 in bit 15 of the code keep rapidly changing the speed from plus to minus ( you can program the analog input to fault if it goes negative or drops below 3.5ma)


This is not a closed loop. Reference speed command starts at 800RPM but only achieves 200-300RPM before faulting.


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## gpop (May 14, 2018)

I have in the past seen a autotune fail ( non powerflex ) It was surgested it was caused by a output reactor or someone aborting the autotune while it was running. 

Failing a autotune on one drive is easy but on 2 that seems odd unless something was copied across


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## Keepin R' Wet (5 mo ago)

just the cowboy said:


> What type of SV setup did you do, Static or rotary?
> Static will just bump the shaft like you describe, rotary will run it up to speed.
> I would look at the incoming voltage, unless disabled you can run a drive with single phase in but it will only run a load at less than half the rated hp.


Just Static - Normal operations prior was Inductions V/Hz and this was just a test to say we tried something. Incoming voltage to the drive was 485VAC between each phase. If your looking at incoming voltage to the motor we were looking at only 3-13V before tripping on F9. The motor is currently de-coupled and help up w/ just a motor hoist, we are preventing to do all the tests on Induction SV due to the instability of the hoist and w/ a 175HP motor (oil cooled) it already jumps when we put a JOG to the motor.


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## just the cowboy (Sep 4, 2013)

Keepin R' Wet said:


> Just Static - Normal operations prior was Inductions V/Hz and this was just a test to say we tried something. Incoming voltage to the drive was 485VAC between each phase. If your looking at incoming voltage to the motor we were looking at only 3-13V before tripping on F9. The motor is currently de-coupled and help up w/ just a motor hoist, we are preventing to do all the tests on Induction SV due to the instability of the hoist and w/ a 175HP motor (oil cooled) it already jumps when we put a JOG to the motor.


What was the incoming current on each phase, just because you read voltage does not mean it is passing current.
3-13 volts tells me it is going into current limit.


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## Keepin R' Wet (5 mo ago)

just the cowboy said:


> What was the incoming current on each phase, just because you read voltage does not mean it is passing current.
> 3-13 volts tells me it is going into current limit.


Yep, we do see that it goes into current limit in the alarm screen. My power analyzer can only go up to 300A and each of the phases on the analyzer would show OL. I know the drive is averaging the current between each phase so getting an accurate reading isn't available at this moment. Also since the analyzer is digital the meter is picking up the IGBT switching which if I had a better filter you can see that it is making its AC sine wave.


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## just the cowboy (Sep 4, 2013)

Keepin R' Wet said:


> Yep, we do see that it goes into current limit in the alarm screen. My power analyzer can only go up to 300A and each of the phases on the analyzer would show OL. I know the drive is averaging the current between each phase so getting an accurate reading isn't available at this moment. Also since the analyzer is digital the meter is picking up the IGBT switching which if I had a better filter you can see that it is making its AC sine wave.


What does the current on the INCOMING look like. It sounds to me like you lost load carrying capacities of a input phase. 

When you go on line with the software it should tell you what is not factory defaults, look at all of these and the motor information to see if they all line up.

@paulengr will be able to help.


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## Keepin R' Wet (5 mo ago)

gpop said:


> I have in the past seen a autotune fail ( non powerflex ) It was surgested it was caused by a output reactor or someone aborting the autotune while it was running.
> 
> Failing a autotune on one drive is easy but on 2 that seems odd unless something was copied across


You can not auto tune on a V/Hz control but in regards to the parameters between the two drives it was manually entered and not pushed with a download.


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## just the cowboy (Sep 4, 2013)

Keepin R' Wet said:


> You can not auto tune on a V/Hz control but in regards to the parameters between the two drives it was manually entered and not pushed with a download.


As said earlier if issue was before drive change it could of been someone changed something to cause original problem.
That why someone suggested dumping and restarting from scratch and I said do a compare to defaults. If someone changed HP/amps setting by mistake this would explain why you go into current limit. We have seen this many times on here and it fixes issues.


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## Keepin R' Wet (5 mo ago)

just the cowboy said:


> As said earlier if issue was before drive change it could of been someone changed something to cause original problem.
> That why someone suggested dumping and restarting from scratch and I said do a compare to defaults. If someone changed HP/amps setting by mistake this would explain why you go into current limit. We have seen this many times on here and it fixes issues.


Parameters set on drive are original since 2015 and have not changed. We store .dno file and last change completed or “saved” was 2015. It is definitely not from someone changing


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## Almost Retired (Sep 14, 2021)

well ..... if it aint the drive ..... and it aint the motor, or the wire to it....
what is left?

have you checked the fall of potential from the top of the supply disconnect to the bottom?
in other words measure volts from wire coming in to wire going out for each phase
also when the motor is not running and the drive is off , turn off the disconnect and check voltage supply to it
if you had a way to connect a single phase load, like a 277 lite bulb, that would show at least some current available

also go further back than the supply disconnect and physically look at connections, as far back as you can where it only affects this one circuit
if there is anything wrong there should at least be some minor visual indications


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## Keepin R' Wet (5 mo ago)

Almost Retired said:


> well ..... if it aint the drive ..... and it aint the motor, or the wire to it....
> what is left?
> 
> have you checked the fall of potential from the top of the supply disconnect to the bottom?
> ...


So I checked input voltage today w/ the power analyzer… voltage was 478.Xx between each phase, current was 47A on A/B and only 20.5A on C phase so there is an imbalance.. checked the scr’s again and all looked good. Fuses and wiring all checked out fine too.


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## Almost Retired (Sep 14, 2021)

Keepin R' Wet said:


> So I checked input voltage today w/ the power analyzer… voltage was 478.Xx between each phase, current was 47A on A/B and only 20.5A on C phase so there is an imbalance.. checked the scr’s again and all looked good. Fuses and wiring all checked out fine too.


@JRaef


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## gpop (May 14, 2018)

Keepin R' Wet said:


> So I checked input voltage today w/ the power analyzer… voltage was 478.Xx between each phase, current was 47A on A/B and only 20.5A on C phase so there is an imbalance.. checked the scr’s again and all looked good. Fuses and wiring all checked out fine too.



input to vfd?


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## gpop (May 14, 2018)

Keepin R' Wet said:


> Parameters set on drive are original since 2015 and have not changed. We store .dno file and last change completed or “saved” was 2015. It is definitely not from someone changing


If you have a drive that's tripped a lot in the past especially on a network then you can end up with memory overflow or corruption in the drive memory. I have sent a drive out for repair as it was doing odd things and they traced it down to memory corruption. Simple factory reset and the drive was returned and put back into service. 
Its probably a mute point in this case as you did not copy the program but its a problem you may encounter in the future especially if you have to re-use a drive.


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## gpop (May 14, 2018)

what is your dc buss voltage. As 3-13 v at the motor seems impossible with a 670 ish buss voltage as the gate would have to be incredibly fast.


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## gpop (May 14, 2018)

Go ahead and factory flash it, power down for 15 mins then program v/h for testing. The more I read the more it seems the drive is stuck in a autotune that refuses to abort.


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## Keepin R' Wet (5 mo ago)

gpop said:


> input to vfd?


Yes


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## Keepin R' Wet (5 mo ago)

gpop said:


> what is your dc buss voltage. As 3-13 v at the motor seems impossible with a 670 ish buss voltage as the gate would have to be incredibly fast.


675DC


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## JRaef (Mar 23, 2009)

No matter what, this is a LOAD side problem. Don't waste any more time and effort on the line side, that would have no relation to what's happening here. The reason you are seeing low current on the input side might be an artifact of the current limiting taking place.

Given that you have replaced everything EXCEPT the cables, I'm leaning toward a cable fault. Most likely it would be a phase-to-phase burn through of the cable insulation, but is NOT going to ground (it would if anything were wet though). So if you are doing a standard ground check with the megger, it doesn't see it. However as soon as the VFD starts sending power to the motor, the current jumps the burn-through phase to phase, the drive reacts to that by current limiting those two phases, the motor acts like it is getting single phase and cogs. Seen it before. So instead of doing the basic megger test where one probe is connected to ground, disconnect BOTH ENDS of the motor leads, then put one probe on one lead, the other on another lead, and do a test at 1,000VDC. You should get between 35 and 100 megohms of resistance between any pair of cables.

Post back what you find out please.


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## just the cowboy (Sep 4, 2013)

JRaef said:


> No matter what, this is a LOAD side problem.
> 
> Given that you have replaced everything EXCEPT the cables, o instead of doing the basic megger test where one probe is connected to ground, disconnect BOTH ENDS of the motor leads .


This is when A S S U M E comes into play. 😃. 
if this is the issue we all assumed he did that basic check.


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## Almost Retired (Sep 14, 2021)

just the cowboy said:


> This is when A S S U M E comes into play. 😃.
> if this is the issue we all assumed he did that basic check.


he did say he meggered the cable, just not the way jraef said to do it


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## Keepin R' Wet (5 mo ago)

JRaef said:


> No matter what, this is a LOAD side problem. Don't waste any more time and effort on the line side, that would have no relation to what's happening here. The reason you are seeing low current on the input side might be an artifact of the current limiting taking place.
> 
> Given that you have replaced everything EXCEPT the cables, I'm leaning toward a cable fault. Most likely it would be a phase-to-phase burn through of the cable insulation, but is NOT going to ground (it would if anything were wet though). So if you are doing a standard ground check with the megger, it doesn't see it. However as soon as the VFD starts sending power to the motor, the current jumps the burn-through phase to phase, the drive reacts to that by current limiting those two phases, the motor acts like it is getting single phase and cogs. Seen it before. So instead of doing the basic megger test where one probe is connected to ground, disconnect BOTH ENDS of the motor leads, then put one probe on one lead, the other on another lead, and do a test at 1,000VDC. You should get between 35 and 100 megohms of resistance between any pair of cables.
> 
> Post back what you find out please.


So I did do a meager check at 1000VDC with cables ends disconnected. The megger test would go to >4000M Ohm. Now the test would instantly go to that reading rather than slowly building but it did to that reading


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## Keepin R' Wet (5 mo ago)

So yesterday I is so playing and tried decreasing flux up time as well as raising it all the way from 0-1 second. Original time was .3851 seconds, and these changes had no change, instant transistor over temp


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## Almost Retired (Sep 14, 2021)

Keepin R' Wet said:


> So I did do a meager check at 1000VDC with cables ends disconnected. The megger test would go to >4000M Ohm. Now the test would instantly go to that reading rather than slowly building but it did to that reading


was that test _phase to phase_ for all three combination pairs ?


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## Keepin R' Wet (5 mo ago)

Almost Retired said:


> was that test _phase to phase_ for all three combination pairs ?


Phase to Phase. I went ahead and did another megger test this morning w/ the load reactor with motor and drive ends removed just to satisfy a recent test….
A-B = 1380M Ohm
A-C = 1180M Ohm
B-C = 1690M Ohm


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## gpop (May 14, 2018)

Did you do a simple resistance test from the drive end with a ohm meter a-b, b-c, c-a to confirm the motor has continuity (load reactor is not open on one phase or a hidden junction)

I just don't see how you are reading so many amps on the incoming yet are unable to find where they are beings used. Front side seems to be converting them to DC according to the buss voltage and it hasn't caught on fire which would be expected as a result of burning 20+kw of energy.
Drive isn't screaming hardware undercurrent (unless you have disabled something and you don't seem to want to share the not at default code but either way i believe hardware undercurrent can not be disabled)
So single phasing, running at zero hertz, funky programming or wiring something wrong seems to be the only explanation and you are converting kw to heat in the motor. (anywhere else you would expect to see smoke)


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## JRaef (Mar 23, 2009)

Huh. Well there goes that theory then.

Now that you have disconnected and connected everything again, try doing another static autotune. I’ve had that happen once where I think there was something going on that allowed the autotune, but it was a bad reading which affected operation. Did the “windows method” of redoing everything and it worked. No idea what the original problem was but the only thing we had done was disconnect everything for tests, reconnect and do another autotune.


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## micromind (Aug 11, 2007)

Bad transistor heatsink temp sensor?

What does it use for AC to DC conversion? Basic diodes or SCRs? One incoming phase current lower than the others suggests a bad diode or SCR on that phase. An oscilloscope looking at current would confirm or deny. 

How is the overtemp code derived? In my experience (somewhat limited......lol) just because a fault appears doesn't mean it's that exact fault. For example, most VFDs don't use voltage or current for a loss of input phase, they use DC ripple. 

I'd try disabling incoming phase loss protection and see what happens.


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## Keepin R' Wet (5 mo ago)

So yesterday we started to pull sections of the gearbox apart and we are pulling the turbine back off the gearbox. The gearbox appears to be locked.... with that being said could explain our issues from the beginning but not with the starter motor de-coupled. Once this is all done I should know more which will be a few days... could we have smoked the motor/VFD w/ a locked gearbox? We'll see......


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## gpop (May 14, 2018)

shouldn't have damaged nothing as the vfd safety's would have kicked in. Would have screwed the autotune if the rotor was unable to turn.


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## Keepin R' Wet (5 mo ago)

So we did find damage in the gearbox to prevent spin… then went ahead and looked at the parameters again a I think P440 “Motor Overload Action” is set on Ignore. Could the drive be smoked for larger current motor now but able to run a 2A motor (15HP) just fine? Smoked 2 VFD’s with the over load action disables? I mean I’m glad we found a problem but haven’t figured out why the motor won’t turn anymore even de-coupled.


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## gpop (May 14, 2018)

Keepin R' Wet said:


> So we did find damage in the gearbox to prevent spin… then went ahead and looked at the parameters again a I think P440 “Motor Overload Action” is set on Ignore. Could the drive be smoked for larger current motor now but able to run a 2A motor (15HP) just fine? Smoked 2 VFD’s with the over load action disables? I mean I’m glad we found a problem but haven’t figured out why the motor won’t turn anymore even de-coupled.


did you factory reset the drive? Until you have done that we can not help you as most of us have fat fingered a drive to the point it will not run. Start with the minimum amount of programming required to make the drive run and make sure you reboot after the factory reset and before programming.


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## Keepin R' Wet (5 mo ago)

So an update since the gearbox is seized I have not made it a priority working on the drive as engineering has taken the wand. I have got back to the troubleshooting the drive now so.... this is what is going on now:


The motor is de-coupled and mounted to the floor w/ no load on it.
Temporary cables have been wired from the drive to the motor.
When completed an 800RPM "start" the motor sometimes starts and other times fails, very inconsistent. Failure meaning that the motor turns about a 1/4 of turn and stops while the drive allows a 2nd attempt because of our attempts setpoint. While each failure we get transistor over temp alarm. When the motor does have a successful start there are no over temp alarms.
A factory reset has been completed prior to start attempts.
So my question, is there by chance that I need LOAD on the motor to get successful starts? I have looked at the parameter sheet and don't see anything sticking out at me that would prevent the VFD to start a motor without a load on it. Though I find this unlikely I have found weirder things on these newer VFD's in my previous troubleshooting.


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## gpop (May 14, 2018)

Drive can be programmed to detect load loss but that's not the alarm you are getting. 

Please post the not at default program list.


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## paulengr (Oct 8, 2017)

There are a ton of parameters that can get you into serious trouble if you don’t know what you are doing. Copy the settings. Factory wipe. Load only motor parameters and autotune. Set for keypad control and try running it. If it runs that way it’s not a hardware issue. If it doesn’t address the hardware.

There are three or four reasons for a drive overheating issue. One is a bad transistor. Second is a bad sensor. These are usually fatal…it’s generally not worth attempting to repair drives unless it’s over 500 HP or so where you get into modular construction and the drive costs tens of thousands. You can tell because you won’t have any other issues.

First let’s get programming out of the way. Copy all the settings. Now factory reset it. Set ONLY the motor name plate stuff. Put it in keypad control and start/run it. If there are no issues you have a programming issue. Review the changes settings. Fix whatever is wrong. If not just reload the original settings. You can easily do this using the keypad as a memory card.

Next check incoming power to the inverter. Look for two power terminals labeled with a + and a - sign. Drives may have various DC bus terminals but these two are what you want. Put your multimeter on them with the drive powered up. First check DC. The voltage should match the drive DC bus reading. If not either you are on the wrong terminals of the drive is defective. Next put it in AC mode and measure ripple. This should be less than 10 V, preferably 1-2 V at most. If not either you have an incoming power problem or a blown rectifier. Test AC voltage. They should be less than 1% different so single digits readings.

Somewhere along here check that all the fans are working and that the heat sink is clean. More than once I’ve replace a fan, cleaned clogged filters, or vacuumed heat sinks and solved major issues.

Next with it running check output voltage and current. Need an AC meter with “Low pass” or “true RMS” for this. All currents should be under 1-2% different. Same with voltages. Again you can compare to drive readings but don’t take the drive readings as gospel.


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## Keepin R' Wet (5 mo ago)

paulengr said:


> There are a ton of parameters that can get you into serious trouble if you don’t know what you are doing. Copy the settings. Factory wipe. Load only motor parameters and autotune. Set for keypad control and try running it. If it runs that way it’s not a hardware issue. If it doesn’t address the hardware.
> 
> There are three or four reasons for a drive overheating issue. One is a bad transistor. Second is a bad sensor. These are usually fatal…it’s generally not worth attempting to repair drives unless it’s over 500 HP or so where you get into modular construction and the drive costs tens of thousands. You can tell because you won’t have any other issues.
> 
> ...


Keypad control for a Powerflex 753?


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## paulengr (Oct 8, 2017)

Keepin R' Wet said:


> Keypad control for a Powerflex 753?


Yes.









PowerFlex 753 AC Drives | Allen-Bradley


Our PowerFlex® 753 AC Drives are cost-effective and easy to use in general purpose applications requiring safety features.




www.rockwellautomation.com





You could use their software control too if you got comms working. Whatever it takes to run it. Keypads are optional with AB, and expensive. As a field tech I don’t consider them optional. I have a box of spares from different brands on the truck. Often the displays are broken or faded so I bring my own.

Then watch your transistor temps. They should decrease while running if you can see them.

It’s helpful also to eliminate the motor. I’d run a PdMA or Baker test but I understand if you don’t have that equipment or access. This just takes the motor out of question.

Forgot to mention while testing, put an amp clamp around all 3 cables and measure ground current. Should be under 10% of total current. Measure the ground lead. Both should be about the same number (no stray currents). This isn’t looking for bearing currents just overall common mode.

If this all passes overall you’ve got a healthy system other than doing testing under load. If not then your drive has issues.


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## paulengr (Oct 8, 2017)

Also DC bus voltage should be 145% of line to line voltage.

If you want to check components first check voltage on the DC bus. Make sure it is dead. Then test capacitance + to -. It’s hard to do much with this though without an identical drive or factory information. Should be within 20% of the “correct” value.

Next check all your antiparallel diodes. Put your meter on diode mode. Put one probe on + and then the other on L1/2/3.:, then T1/2/3. Reverse the leads and repeat. Then put it on the - terminal and do it all again. You should read 0.3 to 0.8 V in the forward direction and “open” in the other direction. You should see an obvious pattern and all 3 phases should measure the same way, both positive and negative. Nothing has to be disconnected for any of these tests. Now switch to ohms. For this test you need a meter that reads into the Megaohms, NOT a “Megger” just an instrument/HVAC style meter. Measure in the direction opposite what you got earlier with the diode tests. All 6 readings on the inverter (12 with an AFE) should be identical. That covers everything except gate checks which you can’t do externally. Generally if you have a failed transistor or diode it is very obvious doing these tests and the tests take a couple minutes. I don’t usually write them down because I’m just comparing. If I do a set of tests I expect all 3 phases to act the same. The L’s and T’s not but L, L2, and L3 should be the same.

If you see a discrepancy double check but this is positive the drive is bad. You can also have IO issues (bad voltage sensor) but no good way to detect that except comparing your readings to the drive readings…see previous post.


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