3 Phase Motor Failure
3 Phase Motor Failure
(OP)
Good Day!
we have an electric motor coupled to a blower for almost 2 months and then the fault happened: burnt terminal wire.
Supply Voltage Measured:230/237/234
Unfortunately we can't measure current.
We tried to jog it but the situation get worst, Line side Line 1 of the main breaker, burnt!
We checked the motor connection and found out that Line 1 and Line3 of the 6 Wire YD connection was interchanged.(diagram attached)
Motor Details:
HP: 10
Phase: 3
Voltage: 220/380/440V (220V YD Connected)
Ampere: 26
RPM: 1800
Hz: 60
Controller: Wye Delta 40A 220V
Why did the motor controller: Breaker, contactor, OL relay and any of the control wire didn't get any damage. Instead the line side of the Main Breaker supplying the controller got burnt.
What do you guys think?
we have an electric motor coupled to a blower for almost 2 months and then the fault happened: burnt terminal wire.
Supply Voltage Measured:230/237/234
Unfortunately we can't measure current.
We tried to jog it but the situation get worst, Line side Line 1 of the main breaker, burnt!
We checked the motor connection and found out that Line 1 and Line3 of the 6 Wire YD connection was interchanged.(diagram attached)
Motor Details:
HP: 10
Phase: 3
Voltage: 220/380/440V (220V YD Connected)
Ampere: 26
RPM: 1800
Hz: 60
Controller: Wye Delta 40A 220V
Why did the motor controller: Breaker, contactor, OL relay and any of the control wire didn't get any damage. Instead the line side of the Main Breaker supplying the controller got burnt.
What do you guys think?





RE: 3 Phase Motor Failure
Loose connections generally cause heating and burn damage to the wires and hardware.
Bill
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"Why not the best?"
Jimmy Carter
RE: 3 Phase Motor Failure
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If we learn from our mistakes I'm getting a great education!
RE: 3 Phase Motor Failure
Your situation is already bordering on a serious fire hazard, you need to hire a qualified professional to analyze the situation and come up with a cause and remedy before you kill someone.
Sorry.
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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RE: 3 Phase Motor Failure
I don't see the failure in the picture but you should never re-apply power to a damaged electric circuit without doing proper repairs first.
Line 1 on the breaker would burn if there was a crappy connection there. It could also be a crappy breaker or a breaker not rated for the application.
RE: 3 Phase Motor Failure
It was engineers that designed that POS. I'd rewind it and just bring the leads out, and eliminate the terminal block.
RE: 3 Phase Motor Failure
However, the picture of the motor junction box that you provided appears to show six leads coming from your controller to the six motor terminals. This seems to indicate that you have a reduced voltage, wye-delta starter. Your nameplate supports this idea because it shows a wye-delta connection for a single voltage. I am thinking that you have starter leads coming to your motor terminals that are T1, T2, T3, T4, T5, and T6 going to a reduced voltage wye-delta starter.
In this case, the phase rotation of the T1-T3 leads must correspond to the phase rotation of the T4-T6 leads. If T1 and T3 are swapped without T4 and T6 also swapping then you will have problems.
This may account for the overheated terminals but normally the motor overloads will interrupt the process first and someone will notice the problem before two months has passed.
RE: 3 Phase Motor Failure
Info that i provided the other day was based on the report given to me.Upon thorough inspection, loose connection was found at main breaker load side.
@lionel, you're right sir.
@ ratcher, yes apparently they did swapped T4 and T6.
Here's what happened.
Client reported to us that the motor terminal connection got burnt.
Upon visual inspection, one of the terminal connection was damaged.
Controller did not trip.
Neither the main breaker.
Actions Taken.
Insulation Test: >550Mohms Line-Ground on all phases.
Voltage Measured: 222/224/227V
Controller rechecked by the supplier
Reconnected the motor terminals.
Main reason why, they tried to jogged it.
The motor did run at first, then the main feeder line supplying the controller to the motor, got burnt.
And guess what, loose terminal connection. How should we know? We only supplied them the motor and controller. Main Breaker and feederline was far from our reach and was assumed stable. And yes, our technician is facing the charges. Cheers!
RE: 3 Phase Motor Failure
By the way, it's not surprising that the breaker didn't trip, if the motor connection never went to ground, the current may never have exceeded the breaker rating even though the heat in the connection caused it to burn.
An IR scan after installation may have picked up the problem before damage was done. A solid state overload relay that could pick up phase imbalance would have likely prevented collateral damage as well.
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: 3 Phase Motor Failure
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(2B)+(2B)' ?
RE: 3 Phase Motor Failure
Secondly: Somebody didn't tighten it up properly!