Three Phase 480V Motor Help

[robbieb2009]

Motor: Cemp AB30 | 280 Delta 7.36A / 480 Wye 4.25A | 2.2kW 60Hz.

Measured Incoming Voltages: L-N: 267VAC and L-L: ~467VAC.

Background: Motor was repaired and repair company said they wired the motor up for 480 only internally. They changed it from 6 wires going into the motor internally to only three so no real need for junction box at motor terminals anymore.

Issue: This motor is used for exhaust ventilation on an oven here at the plant to get rid of unwanted VOC's. It is not pulling enough air out. The damper on the intake is set at ~1/4 open right now and its pulling 4A. When the damper is fully opened the current rises to 8-8.5A before it eventually trips the 4A protection circuit.

Question: Is there a way to actually find out what way the repair company wired the motor? If they did wye then I'm assuming I'll need to go to a higher power motor but if they wired it for delta internally by accident I could just switch to a 8A breaker.

What would you guys recommend? I'm a mechanical engineer by nature so I am no where near very knowledgeable on electrical.

Thanks,

Robbie

 

[tom baker]

I recommend getting your plant electrician or electrical contractor to assist.

 

[robbieb2009]

Thanks for the reply! There isn't a plant electrician. I could get a contractor to come in but would like to exhaust all other available options first.

 

[tom baker]

Well this is almost a DIY question which we don't allow.

 

[junkhound]

Since thread not closed, re:
Is there a way to actually find out what way the repair company wired the motor?

Did the rewind company give yu a diagram of the windings? If not, why not? etc.. Yes, take it apart, count turns in slots, notice how windings lay is slots, how the windings interconnect, delta, wye, etc.. etc...
Few electricians and even fewer engineers would be able to do so in a reasonable amount of time.

 

[robbieb2009]

There are electrical testing trained personnel here just not certified electricians by trade. I wouldn't do the testing myself as I don't feel comfortable or trained. The exhaust from this oven blows over into a paint booth. Then that booth has a 7.5kW motor on the exhaust (compared to 2.2kW on oven). We are also thinking that motor could be pulling air through the oven motor thus increasing the speed/flow on it causing the amperage to rise. Have to test that theory when the line is down.

 

[ActionDave]

Since the motor is running on 480V it should it almost certainly is wired wye or it would burn up. There's no easy way to check without opening up the motor and no, you can't use an 8A fuse to protect a motor that's rated at 4A.

 

[ActionDave]

There are electrical testing trained personnel here just not certified electricians by trade. I wouldn't do the testing myself as I don't feel comfortable or trained. The exhaust from this oven blows over into a paint booth. Then that booth has a 7.5kW motor on the exhaust (compared to 2.2kW on oven). We are also thinking that motor could be pulling air through the oven motor thus increasing the speed/flow on it causing the amperage to rise. Have to test that theory when the line is down.

There's your problem right there. You're moving too much air.

 

[robbieb2009]

Did the rewind company give yu a diagram of the windings? If not, why not? etc.. Yes, take it apart, count turns in slots, notice how windings lay is slots, how the windings interconnect, delta, wye, etc.. etc...
Few electricians and even fewer engineers would be able to do so in a reasonable amount of time.

I'll ask them about that now! It's almost in constant operation so that would be hard but could definitely do it to a repaired spare they did to see if they are correct.

 

[robbieb2009]

[/COLOR]
There's your problem right there. You're moving too much air.

Not 100% on that as this oven/booth setup is repeated a couple times on the line and this problem is only happening at this oven (blowing air out the oven) while others are being stagnant or in flowing. And same 7.5kW exhaust is on all the booths. Is a complex problem.

 

[gar]

190730-1302 EDT

robbieb2009:

You list yourself as a "project engineer". What is that? Are you an electrical engineer? If so pull out your textbook on AC machinery and study it a little to satisfy Tom Baker.

In the original winding method the motor was designed to work at 280 V in delta connection, and thus in wye connection it would be 480 V, same voltage per coil in either connection.

.

 

[ActionDave]

Not 100% on that as this oven/booth setup is repeated a couple times on the line and this problem is only happening at this oven (blowing air out the oven) while others are being stagnant or in flowing. And same 7.5kW exhaust is on all the booths. Is a complex problem.

Well it's a classic case of moving to much air. You damp down the fan and the load lowers.

I re read your description of the set up again. To be clear, are the two fans in tandom?

 

[robbieb2009]

Well it's a classic case of moving to much air. You damp down the fan and the load lowers.

I re read your description of the set up again. To be clear, are the two fans in tandom?

Yes they are cascaded into each other. The exhaust flows from the oven 2.2kW into the booth as intake then the 7.5kW takes exhaust out of the booth.

 

[LarryFine]

Question: Is there a way to actually find out what way the repair company wired the motor?

Why not just take the motor back to the repair place?

 

[synchro]

If the other oven/booth setups are the same or very similar, then measuring the current draw on those oven exhaust blowers could provide a baseline for comparison. For example, if they're working fine with significantly less current then something is probably wrong with the motor in question, there could be blockage in the airflow path, etc.

 

[Besoeker3]

Motor: Cemp AB30 | 280 Delta 7.36A / 480 Wye 4.25A | 2.2kW 60Hz.

Measured Incoming Voltages: L-N: 267VAC and L-L: ~467VAC.

Background: Motor was repaired and repair company said they wired the motor up for 480 only internally. They changed it from 6 wires going into the motor internally to only three so no real need for junction box at motor terminals anymore.

Replace the motor with new. Can it really be commercially viable to put much time into such a small motor?

 

[iceworm]

Replace the motor with new. Can it really be commercially viable to put much time into such a small motor?

VOCs, spray booths, so maybe explosion proof. if so, yeah, maybe that is why they had it rewound.

 

[Jraef]

Replace the motor with new. Can it really be commercially viable to put much time into such a small motor?

Yeah, no kidding. Every hour you spend on this motor is an hour wasted, it's not worth it.

As a general rule though, I think your motor was sized based on the required air flow, as set by the damper position. In a centrifugal machine like a blower / fan, load = flow. So opening the damper for more flow is pushing your motor into overload because it was not selected to have that happen to the blower. If the motor were connected in delta and you applied 480V to it, the motor would saturate and likely almost immediately overload without a change in the air flow. Take a look at this chart of the effects of voltage variation on an AC induction motor, particularly the line for FL Amps. This chart only goes up to +15%, at 480V on a 277V winding pattern, you would be putting +58% voltage, so you can extrapolate out what effect that would have on the motor!