Compressor arc-ing on start up

[GarageGuy89]

5 hp motor arcs in same spot to the tank/mounting plate on start up. Usually happens 50% of the time. It's always a single quick spark/arc.

Common sense tells me this is not good, what would you guys recommend I do? I've blown it out with air, but have not disassembled. Not sure what causes this...

 

[Bert_]

Probably have to do at least a little more investigating before you'll get any helpful information.

Usually this sort of thing will only get worse.

Is it from inside the motor or just from a wiring/ junction box?

 

[matt_i]

I think the windings are decayed somewhere and energy is "leaking" to ground on the high inrush/ large back-emf startup.

Its possible they could be dipped and baked by a motor shop but I think it would be cheaper to source a new motor.

I think eventually its going to trip a breaker, and then mostly trip the breaker after that.

 

[mm08822]

Provide a marked up pic of where arc is occurring and motor nameplate.
Check all connections and especially ground connections.
This includes a good inspection of motor leads and wiring to/from centrifugal switch.
Assuming the motor has capacitors, inspect them and wiring.

 

[wyliesdiesels]

Is the motor properly grounded?

If not and one of the windings is contacting the enclosure/housing, when the motor contacts the metal frame, its causing a momentary short.

Is the motor on rubber insulators?

 

[GarageGuy89]

Arc is happening at lower left corner. Middle of the fins, just below that lower left hand bolt in the photo


Sent from my iPhone using Tapatalk

 

[mm08822]

Arc is happening at lower left corner. Middle of the fins, just below that lower left hand bolt in the photo


Sent from my iPhone using Tapatalk

It could be you are seeing the centrifugal switch opening and the resulting arc.

Look at caps. Look at switch contacts and ability of switch to open without hanging up on rust and dust.

 

[theoldwizard1]

It could be you are seeing the centrifugal switch opening and the resulting arc.

Concur ! Unless the arc is flashing outside of the housing, don't worry about it.

 

[wyliesdiesels]

It could be you are seeing the centrifugal switch opening and the resulting arc.

Look at caps. Look at switch contacts and ability of switch to open without hanging up on rust and dust.

Now that i see the pic, I have to agree with you.

Motor is directly bolted to comp frame, so arc would not be possible.

 

[GarageGuy89]

Now that i see the pic, I have to agree with you.

Motor is directly bolted to comp frame, so arc would not be possible.

So is this normal? Or should I be cleaning something?

The compressor used to power an old wooden boat shop for 20+ years, so there is wood and fiberglass dust caked everywhere. It's almost like a coating of paint...wouldn't be surprised if the motor is covered in it as well.

aoldmachinenut; I'll check when I get some time this weekend. I believe the compressor is from the mid 80's though.

 

[mm08822]

So is this normal? Or should I be cleaning something?

The compressor used to power an old wooden boat shop for 20+ years, so there is wood and fiberglass dust caked everywhere. It's almost like a coating of paint...wouldn't be surprised if the motor is covered in it as well.

aoldmachinenut; I'll check when I get some time this weekend. I believe the compressor is from the mid 80's though.

It could be you are seeing the centrifugal switch opening and the resulting arc.

Look at caps. Look at switch contacts and ability of switch to open without hanging up on rust and dust.

Fill compressor with air and once full kill power to compressor.
Remove/untension belt and remove endbell carefully. Blow out motor windings, cent switch/end bell insides.
Verify cent switch actuator can easily slide on shaft. You be able to see a path where movement occurs. Clean that area with steel wool or emery paper.
Blow out that cleaned area with air and the gap in between actuator and shaft.
Look at cent switch contacts. Are they heavily pitted?

Re-assemble all and run compressor.

 

[GarageGuy89]

Is that a Westinghouse motor? I have a huge 5 hp single phase cap start/cap run Westinghouse that I am going to put on my compressor, i cannot find any info on it. It appears to be from the early 60's and looks very similar to yours, mine has an external square capacitor box. I know my post is no help to you I just noticed the similarity to my motor.

Motor is a MagneTek Century Electric