Starter Failure

Me and my coworkers have been troubleshooting a starter failure for a Cutler Hammer Soft Starter for a 100hp motor. The motor when put in either Hand or Auto will start and after 2 seconds a timer instruction in the PLC will cause a Starter failure. The motor has just enough time to get past its inrush current before it causes the starter failure. In the PLC if it does not see a Starter Energize Bit it will cause the timer to time out and cause a failure alarm. We have megged the motor leads and windings, test was good. All fuses are good. This is a brand new starter, it was replaced 3 days ago because the old starter's contacts were very badly pitted. This is one of 2 motors that are supposed to work simultaneously and there is a 5 second delay as not to cause a large surge on the generator. They are pipeline pump motors that were upgraded from 60hp because of the load. I hope this is enough information about the situation. Any suggestions would be helpful, thanks.

scadadavid,

i may be wrong, but you do not have the same setup.
100 hp vs 60 hp. the parameters in my opinion should be different.

you say the motor will start and fault out after 2 seconds.
what signal is telling this timer to start and cause a fault?
look at the logic and ask what would happen if i increased this timer to 10 or 20 seconds? i think this is the next step in your debug process.

regards,
james

Did you forget to wire the auxilliary contact of the starter back to a PLC input? Did you accidently use a NC as opposed to a NO or vise versa?

Parameters have all since been changed and upgraded by a programmer and the pump has been running for 4 months with no problems since the upgrade from 60hp to 100hp.

There is not a signal telling the PLC to fault, its the absence of a signal. The PLC is not seeing that the Starter is engergized for 2 seconds and it causes it to fault.

I'm not allowed to change the program without approval from the company and I am hesitant to do that since it did work before for 4 months with this setting.

The Auxillary contacts have not been altered since the change from the pitted contact starter. The Contacts are on a separate component that stab in the sides of the starter and they haven't been changed since the last starter. But that is an idea Thank you.

The problems seems to be coming from whatever the input is for the PLC to fault out the starter. The contacts may not have been altered, but they could be sticking, not functioning, loose wire, burnt fuse, etc. The PLC is doing what what it is programmed to do based on the feedback it's getting. That feedback is where your fault is.

In the PLC if it does not see a Starter Energize Bit it will cause the timer to time out and cause a failure alarm

Look at the schematics - where does this bit come from?
If it is a contact on the starter or contactor check that it has the correct voltage (or absence of voltage).
Is there an Input LED - does it come on?

Just a thought....
we had a similar issue after replacing a freedom series FVNR starter to a Soft start on Devicenet.
the bit used for starter pulled ( or running ) is delayed until full across the line voltage is achieved.

so if the PLC is looking for the run bit to happen sooner you may have to adjust for it.

Yes I agree that it is a feedback problem.
We are going to investigate this... Stay tuned.

Problem led back from the starter and in tracing out the line found a slew of blown fuses, on a separate issue weve been having problems with the platform's generator and it must have surged the system so many times and blown several fuses on the PLC side. We had been checking all the fuses on the MCC side prior to this.

The Auxillary contacts have not been altered since the change from the pitted contact starter. The Contacts are on a separate component that stab in the sides of the starter and they haven't been changed since the last starter.

Click to expand...

The auxiliary contacts may not have been changed, but the starter itself WAS changed, so therefore the aux block had to be removed and reinstalled on the new starter, and all starters are not created equal. The auxiliary contact operating mechanism on your new starter may very well be user programmable, or may operate differently than the old one, or the auxiliary contact block could have been plugged into a different side or place than the old set-up. On many starters, simply reversing the aux block changes the operation from NC to NO.

For the Cutler Hammer S611 Soft Starter:

Click to expand...

Using Auxiliary Contacts.
The S611 soft starter contains two (2) auxiliary contacts to indicate status. Both relays have user defined attributes. Relay contact configuration is selectable in the Advanced configuration Menu. Relay 1 uses contacts 13 and 14. The following contact configurations are available for Relay 1:
0 = Faulted

1 = Not faulted
2 = Run (in bypass)—default value
3 = Not in bypass
4 = Motor energized

5 = Motor not energized​

Click to expand...

scadadavid said:

Parameters have all since been changed and upgraded by a programmer and the pump has been running for 4 months with no problems since the upgrade from 60hp to 100hp.

There is not a signal telling the PLC to fault, its the absence of a signal. The PLC is not seeing that the Starter is engergized for 2 seconds and it causes it to fault.

I'm not allowed to change the program without approval from the company and I am hesitant to do that since it did work before for 4 months with this setting.

The Auxillary contacts have not been altered since the change from the pitted contact starter. The Contacts are on a separate component that stab in the sides of the starter and they haven't been changed since the last starter. But that is an idea Thank you.

Click to expand...

Hmm ran for 4 months and then problems? Any idea when all those fuses that you mentioned blew?

Maybe a long shot and maybe not. What are the distances involved here? If long wire runs with a fair amount of resistance and other connections getting a bit more resistance each could they total to too much IR drop?

Dan Bentler

Distance is about 60 feet from MCC bucket to peckerhead.

is this contact on the start contactor or the bypass contactor
Also have you measured the PLC input to see if the signal is being actuallt reveived at any time

What I did to find out whether or not the PLC was seeing the Starter energize was holding the plunger in on the starter and seeing if the led lit up on the input bit LED on the front of the card, didn't light up. Then I did the same thing and seen if the bit on the ladder became true when pushing in the plunger, it did not. I traced the wiring, found the fuses changed them out. Problem solved.