Help with powerflex 753, input phase loss

[bm589]

Hi all,

I am having a problem with a powerflex 753 we have on site and keep getting input phase loss. The drive has been running for a long time, maybe 5 years, but probably more with no issues. It is a 45kW ND. It is running the main motor for an aluminum cupping press. The fault only happens when it goes into high speed (only 42ish amps in high speed) and only after approx 5 mins of high speed running and only been happening the last few days. I've tried the following to rectify the problem but not having any success.
-Increasing p463 from default (325) to 400, didn't want to go too high and risk damaging the drive.
-Replacing for a brand new drive
-Replacing the circuit breaker feeding drive
-Checked all connections, all fine
-Incoming voltages are good, only 20mA dropped over the CB on all phases
-Other drive in the same board has no issues

Unfortunately, don't have access to power monitoring equipment to watch incoming power. Doesn't have a filter installed but has been working fine for years so I don't think that is the problem.

Any help would be much appreciated.

Cheers

 

[Ken Moore]

It is most likely the drive failing. But, have you added any 3phase equipment lately? Could something else, be causing "issues" on the incoming power. Have tried an upstream reactor?

 

[bm589]

I did think initially that it would be the drive failing, but since putting in a brand new one and still getting the same fault I'm a bit lost for ideas. Have you seen many drives fail straight out of the box? We do have another brand new one we could try. No new equipment, the switchboard the drive is in has been unchanged for many years. Have not tried a reactor yet, I will have to check if we have one onsite suitable to try.

 

[kekrahulik]

You say that you don't have power monitoring equipment - what sort of voltmeter do you have? I have a Fluke multimeter that I can connect to the incoming phase-phase or phase-ground and then set the meter to capture min/max. So after connecting it, resetting min/max, you can check it after a fault to see if the min voltage did actually drop. Depending how long you have to wait, my meter goes to sleep, but I can disable that.

 

[Cheeseface]

I ran into this a while ago, Rockwell has a really good technote on this. To sum it up, this fault is detected by ripple on the DC bus.

Recall the incoming 3-phase is rectified to DC then switched rapidly to produce AC on the output side.

DC ripple occurs when the rectification doesn't produce smooth DC. In my case, it was happening because the largest difference between phases was more than 2 or 3%.

According to the technote, this produces heating in the caps which shortens the life of the drive, hence the shutdown. There's other reasons for it to happen, but the problem is coming entirely from the input side of the drive.

ed: i take that back about entirely on the input side. the technote talks about a bad encoder feeding back into the dc bus, bad bearings, improper dynamic brake settings, ...

 

[bm589]

You say that you don't have power monitoring equipment - what sort of voltmeter do you have? I have a Fluke multimeter that I can connect to the incoming phase-phase or phase-ground and then set the meter to capture min/max. So after connecting it, resetting min/max, you can check it after a fault to see if the min voltage did actually drop. Depending how long you have to wait, my meter goes to sleep, but I can disable that.

I do have a Fluke multimeter but it doesn't have function.

 

[bm589]

I ran into this a while ago, Rockwell has a really good technote on this. To sum it up, this fault is detected by ripple on the DC bus.

Recall the incoming 3-phase is rectified to DC then switched rapidly to produce AC on the output side.

DC ripple occurs when the rectification doesn't produce smooth DC. In my case, it was happening because the largest difference between phases was more than 2 or 3%.

According to the technote, this produces heating in the caps which shortens the life of the drive, hence the shutdown. There's other reasons for it to happen, but the problem is coming entirely from the input side of the drive.

ed: i take that back about entirely on the input side. the technote talks about a bad encoder feeding back into the dc bus, bad bearings, improper dynamic brake settings, ...

I did read about that is something to do with the DC bus voltage but couldn't really find much information that goes into detail.

We have since increased P463 up to 650 which you can do safely without harming the drive apparently, and it hasn't faulted since. Still a bit strange as it has been running a long time without and problems. Next time we have a chance to shut it down I will have a look at the bearings.

 

[Cheeseface]

In my case, one of the phases was being pulled low (12V difference) by air conditioning units. The problem went away in winter.