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Discussion Starter · #1 · (Edited)
Breaker keeps tripping

Hello! I have an issue that I have been troubleshooting for a few days now and was hoping to pick a few brains to see if anyone has a suggestion. I have a pretty basic electrical system that runs a small motor (essentially a 50HP, 440Vac, 3 phase, 2 speed motor and brake) that keeps tripping its circuit breaker. Insulation and continuity checks on the motor were good-500 Megaohms and a 0% difference in winding continuity.

This circuit has 5 relays that allow the motor to run in fast, slow, reverse, and forward and a maintaining relay. Also, a thermodector is in the mix.

The supply breaker had been replaced, switch has been taken apart and continuity checked, and as stated above motor has checked out.

The break is electrically released and spring set and I did a resistance check on the break solenoid and got a resistance of about 24 ohms. Not 100% sure what this number means. I don't have too much experience working with solenoids.

I also did a visual inspection of all the circuitry and there were a few loose connections that I tightened up and lugs that needed to be replaced.

I haven't retested the switch because I wanted to do everything I could before returning power. Without seriously taking apart any of the equipment is there anything else I can check?! Also and I missing something with the solenoid.
 

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The brake system is usually more than just a coil, the brake coils are usually DC, so before the coil is a rectifier. Checking resistance into the rectifier has little bearing on whether the coil is functional or not. If the coil is not energizing when the motor energizes, then the brake is still set when you turn on the motor and you will get Locked Rotor Current for a lot longer than if the motor were allowed to spin. Even if the brake coil is getting weak (deteriorating insulation) and releasing the brake too slowly, it can cause the breaker to trip.

There should (might) be a manual release for the brake, see if you can find it and engage it, or remove the brake temporarily for testing, then see if the breaker still trips. If it does, then you have some other issue.
 

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Discussion Starter · #3 · (Edited)
Thank you for your reply JRaef! I have a pretty crappy photo of a schematic that shows the brake solenoid, motor and brake. I could be absolutely incorrect in saying this but to my understanding relays energize downstream of this drawing which shut the BR contacts, energizing the solenoid which then electrically releases the brake...so I don't think any rectifying is happening...but like I said I could be completely wrong!


I really like your idea of disconnecting the brake from the system, but I don't know how I would go about doing that...I'm going to try and get a better photo of the system tomorrow to post.
 

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Hollypoptree said:
Hello! I have an issue that I have been troubleshooting for a few days now and was hoping to pick a few brains to see if anyone has a suggestion. I have a pretty basic electrical system that runs a capstan (essentially a 50HP, 440Vac, 3 phase, 2 speed motor and brake) that keeps tripping its circuit breaker. Insulation and continuity checks on the motor were good-500 Megaohms and a 0% difference in winding continuity.

This circuit has 5 relays that allow the motor to run in fast, slow, reverse, and forward and a maintaining relay. Also, a thermodector, that the tech manual doesn't go into much detail about.

The supply breaker had been replaced, switch has been taken apart and continuity checked, and as stated above motor has checked out.

The break is electrically released and spring set and I did a resistance check on the break solenoid and got a resistance of 24.7 ohms. Not 100% sure what this number means. I don't have too much experience working with solenoids.

I also did a visual inspection of all the circuitry and there were a few loose connections that I tightened up and lugs that needed to be replaced.

I haven't retested the switch because i wanted to do everything I could before returning power and retesting the switch. Without seriously taking apart any of the equipment is there anything else I can check?! Also and I missing something with the solenoid.
No offense, but this isn't an issue for this online forum.

You list yourself as "In the Navy".

PM me please if you need further info.
 

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Hollypoptree said:
Oh okay, I'll try and delete it! Didn't mean to offend anyone.
Your not offending anyone. And most everyone here would be happy to help.
I'm from NavFac and understand were your coming from.
 

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Hollypoptree said:
Oh okay, I'll try and delete it! Didn't mean to offend anyone.
You have to post a few times before you can send or receive a private message.
I think the magic number is 5?
 

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Hollypoptree said:
I'm trying to send you a message now! Thanks!
If it doesn't go thru, post a few replies to this thread and then it will work.
 

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Hollypoptree said:
Hey thanks again, I just sent you a message...hopefully it works!
Ok, haven't gotten it yet.
 

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Hollypoptree said:
Dang. I'll keep posting! ha!
Like I said, you need a few posts before you can send and receive.
Soon you'll make it.
 

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Hollypoptree said:
Thank you, I think this makes 7...
Rats, 7 isn't the lucky minimum number
:(
 

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Can you actually see or even hear the brake mechanism to confirm operation? I agree with Jraef, a good starting point would be to actuate the brake contactor and see if the brake is actually releasing.

Also check to see if there's a manual engagement on the motor: I've replaced more than one brake motor that was destroyed after the brake was manually forced closed.
 

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Discussion Starter · #17 ·
Well, I'll attempt to send you a message tomorrow. I really do appreciate your honesty and forwardness! Time to drink a beer and watch the Heat win!

Big John,

The breaker trips after a few seconds of moving the capstan in the slow forward or reverse direction. My gut feeling in the very beginning was that the motor was 'overheating' because the brake solenoid was failed, causing the brake to stay engaged during operation...overloading the circuit, tripping the breaker...hopefully in a few more days I'll have more information about the issue.
 

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Hollypoptree said:
Well, I'll attempt to send you a message tomorrow. I really do appreciate your honesty and forwardness! Time to drink a beer and watch the Heat win!

Big John,

The breaker trips after a few seconds of moving the capstan in the slow forward or reverse direction. My gut feeling in the very beginning was that the motor was 'overheating' because the brake solenoid was failed, causing the brake to stay engaged during operation...overloading the circuit, tripping the breaker...hopefully in a few more days I'll have more information about the issue.
Jraef & John have great insight.
Talk to you tomorrow.

BTW, welcome to ET, its a great place with good people. You will like it here.
 

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A few ideas:
1. As Jreaf said, verify brake function.
2. At motor peckerhead, check that all three phases are energized at the
motor. ( You will need to disconnect the motor to do this correctly.)
3. There could be an open winding in the motor. ( This would "single phase"
the motor causing a higher current draw.)
4. Check the mechanical driven load for binding or failing bearings. Also, it could be the motor bearings.

What type of overloads are on this motor? Does the breaker trip on start-up, or after running a while?
 

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Hello! I have an issue that I have been troubleshooting for a few days now and was hoping to pick a few brains to see if anyone has a suggestion.
Is there anyone there that operates this machine all of the time and is familiar with its personality? The way it sounds, how it normally starts and stops, the speed, little things like that. It may be easy to tell if something is binding it up. Could it be an external force that is overloading it? You could maybe narrow the problem down to either mechanical or electrical by information from the operator.
 
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