MCP Tripping when motor stopped

Status
Not open for further replies.
M

MrJLH

Senior Member
Location
CO
I have an interesting issue I'm kind of stumped on. I have a MCP tripping when the motor is stopped.

The motor is a loading pump. An operator pre-programs the amount of product into a loading car and a PLC automatically start the pump and stops the pump when loading is complete.

For what ever reason the MCP is tripping after the pump stops when loading is complete.

Any ideas?
 
D

Dale001289

Senior Member
Location
Georgia
MrJLH said:
I have an interesting issue I'm kind of stumped on. I have a MCP tripping when the motor is stopped.

The motor is a loading pump. An operator pre-programs the amount of product into a loading car and a PLC automatically start the pump and stops the pump when loading is complete.

For what ever reason the MCP is tripping after the pump stops when loading is complete.

Any ideas?
Click to expand...


Does the MCP have a shunt trip or undervoltage relay?
 
I

Ingenieur

Senior Member
Location
Earth
what is the product?
can the motor 'regen' as product falls back thru the pump?
is there a check valve, etc, to prevent this?

what protections does it have? oc, toc, gf/0 seq, over-voltage?
 
D

Dale001289

Senior Member
Location
Georgia
MrJLH said:
I have an interesting issue I'm kind of stumped on. I have a MCP tripping when the motor is stopped.

The motor is a loading pump. An operator pre-programs the amount of product into a loading car and a PLC automatically start the pump and stops the pump when loading is complete.

For what ever reason the MCP is tripping after the pump stops when loading is complete.

Any ideas?
Click to expand...

You may have something going bad in the starter -
It could be you are shorting input phases when it opens OR it is arcing badly.
 
M

MrJLH

Senior Member
Location
CO
Ingenieur said:
what is the product?
can the motor 'regen' as product falls back thru the pump?
is there a check valve, etc, to prevent this?

what protections does it have? oc, toc, gf/0 seq, over-voltage?
Click to expand...

Asphalt, no check valves. Not sure about the fall back as our facility is old and this has never happened.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
My first suspicion would be that one (or more) contact in your contactor is broken or severely burned and when the contactor is fully closed, it’s fine but when you open it, the resulting arc is flashing over to another phase.
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Jraef said:
My first suspicion would be that one (or more) contact in your contactor is broken or severely burned and when the contactor is fully closed, it’s fine but when you open it, the resulting arc is flashing over to another phase.
Click to expand...

scary. sounds like one of those situations where the starter cover passes u as u run down the hallway :)
 
petersonra

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Jraef said:
My first suspicion would be that one (or more) contact in your contactor is broken or severely burned and when the contactor is fully closed, it’s fine but when you open it, the resulting arc is flashing over to another phase.
Click to expand...

You should be able to see carbon build-up if that's the case
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
adamscb said:
Completely irrelavent, but you use 480v for your controls? Never heard of that before.
Click to expand...

His diagram shows a 480/120 control transformer, but a lot of the equipment inn this area uses 480v control.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
adamscb said:
Completely irrelavent, but you use 480v for your controls? Never heard of that before.
Click to expand...

For big Size 5 Starters, the coil current st 130V becomes problematic, requiring very large Control Power Transformers. Then in Exp Proof controllers, the heat of those transformers being trapped in a very expensive sealed box adds more problems.
 
A

adamscb

Senior Member
Location
USA
Occupation
EE
AtTheKeyboard said:
adamscb beat me to it.

That 480 tap for controls ahead of the instrumentation transformer looks suspicious - moreso since it's energizing that HOA at 480V. I haven't seen that before either!
Click to expand...

Yeah pretty strange...makes me wonder if the field start/stop has to have arc flash labels applied.

They also must have a pretty beefy PLC, because it's opening/closing contacts that have 480v across them.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
adamscb said:
Yeah pretty strange...makes me wonder if the field start/stop has to have arc flash labels applied.

They also must have a pretty beefy PLC, because it's opening/closing contacts that have 480v across them.
Click to expand...

No, the PLC turns on a relay, probably 24VDC or 120AC coil, the relay contact is in the starter circuit. Machine Tool Telays have contacts rated for 600V.

Full voltage control used to be the norm years ago.
 
Last edited:
M

milldrone

Member
Location
Northern California
MrJLH said:
I have an interesting issue I'm kind of stumped on. I have a MCP tripping when the motor is stopped.

The motor is a loading pump. An operator pre-programs the amount of product into a loading car and a PLC automatically start the pump and stops the pump when loading is complete.

For what ever reason the MCP is tripping after the pump stops when loading is complete.

Any ideas?
Click to expand...

Not sure if this applies to your situation. I was sent to troubleshoot a steam/pressure washer unit. The MCP was tripping after the machine was shut down. We knew this because the operator would turn it off and then it would not start again. The unit had a local push buttons on the control panel and a remote push button control station (more than 500 feet away, no steam use at the remote location) Being a lazy person we tested at the local controls and could not reproduce the problem. Next day the same problem reappeared. When we tested at the remote control station we could reproduce the issue. I should also mention the MCP was one of those IEC style units that combines a disconnect and motor overloads in the same unit. Secondly I also need to mention that the local control panel was mounted on strut about 4 feet long and the unit would flex with pressure applied to the start and stop buttons. Thirdly I need to mention We had no spare parts for the IEC gear and someone had previously hacked a repair using solid wire between the MCP and the contactor. This let the MCP float on the solid core wires.

Now for the kicker: when using the local push buttons the vibration of the less than solidly mounted control panel and MCP/overload combo was damped by the operators fingers on the push buttons. When using the remote station the shock of the contactor pulling out would trip the MCP/overload unit.

MrJLH said:
Fun part with this one is the starter is in a spin top
Click to expand...

This implies that you cannot open this unit while in operation (due to environment). What I'm suggesting is that some "out of the box" troubleshooting/testing may be needed.
 
Last edited:
Status
Not open for further replies.
Top