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Old 03-11-2018, 03:37 PM   #1
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Default Changing a Baldor motor from 240 to 480

I was recently out on a service call to change a machine we built from 240 to 480. Out of three motors a 3/4 a seven and a half and a 40 horsepower. everything in the control panel and the motors had zero problems. Except for the 40 horsepower motor. For some reason trying to start that motor would kick the 200 amp main. that's after passing through my motor protector overload etc etc in the panel. Including passing through a 100-amp and a 200-amp breaker in the service panel. Does anyone have any experience with a motor that's ran on 240 not wanting to convert
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Old 03-11-2018, 06:23 PM   #2
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I was recently out on a service call to change a machine we built from 240 to 480. Out of three motors a 3/4 a seven and a half and a 40 horsepower. everything in the control panel and the motors had zero problems. Except for the 40 horsepower motor. For some reason trying to start that motor would kick the 200 amp main. that's after passing through my motor protector overload etc etc in the panel. Including passing through a 100-amp and a 200-amp breaker in the service panel. Does anyone have any experience with a motor that's ran on 240 not wanting to convert
40 HP @ 480 volts will have pretty good inrush current to start up the motor and if you have 100 amp breaker it may hold up during start up.

However did you double check the connection on the motor peckerhead ( motor junction box ) ?

what kind of load the 40 HP motor try to start on ??
If it was a high intera load it maybe a good idea to install soft starter or VSD ( variable speed drive ) that can reduce the inrush current a bit only after you double check the motor connection to make sure it is in correct conferation.
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Old 03-11-2018, 06:27 PM   #3
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I see four possible issues.

You wired it wrong.
You're using the wrong breaker type/setting.
Wrong starting method.
Mechanical factors.
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Old 03-11-2018, 06:30 PM   #4
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I see four possible issues.

You wired it wrong.
You're using the wrong breaker type/setting.
Wrong starting method.
Mechanical factors.
I am picking on the top two items you posted .,,,
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Old 03-11-2018, 07:01 PM   #5
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CEC rules, but no way are you going over 400% rating for a 40hp !

Less, depending on the OCPD
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Old 03-11-2018, 07:20 PM   #6
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The 2 small motors are most likely 9 lead Y connected. A standard Baldor 40HP will have 9 leads, the open type is Y and the enclosed type is ∆. But it doesn't matter, the 480 connection is the same on both Y and ∆.

The starting current will be somewhere around 330 amps. A 200 amp breaker will easily handle 330 amps to start a motor.

How much current is on the 200 amp main already? Does it have adjustable magnetic trips? Are you positive the motor is connected correctly?

A lot of Baldors have color coded leads. If this one does, blue, white and orange will be the incoming 480. Pink and yellow splice together, black and red splice together and gray and purple splice together.

If it's 12 lead, 9 of the leads might be colored as noted above. The other 3 (10, 11 and 12) will most likely be the same color.

The 480 connection here is L1 = T1&T12. L2 = T2&T10. L3 = T3&T11. T4&T7 splice, T5&T8 splice and T6&T9 splice.

As a side note, in my experience, Siemens breakers seem to have a very low magnetic tripping point. Most of the others are quite a bit higher.

Side note #2.....all the above assumes the motor starts across the lines. If its some sort of reduced voltage starting, the connections will be different. Write back and one of us will provide the proper connections.
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Last edited by micromind; 03-11-2018 at 07:23 PM. Reason: Added side note #2.
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Old 03-11-2018, 07:35 PM   #7
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Currently I was pulled from the field but my guy onsite sent this picture.
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Old 03-11-2018, 07:48 PM   #8
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I see the motor connection is correct as Mircomind explaining on that.

What kind of load the 40 HP motor is try to run on ? as I mention above if you have high intera loads it will draw a bit of current I know most 40 HP motor wired or set up for 400/480 volts system typically draw about 300 to 350 amp during starting mode.

If you have 200 amp breaker tripped during starting mode you may have some load on 480 volt breaker that will affect it.

Did you or your crew have clamp on ampmeter with ya ? if so you may want to check the current drawage during start up.

Once it is running it should be about 40 to 50 amps at 480 volts.

Try to uncouple the load from the motor to see if that spin up good if so maybe the breaker is weak or just cant handle the inrush current.

Please note this part is on for across or direct on line starting.
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Old 03-11-2018, 08:45 PM   #9
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Tell us more about this motor. The breaker/breakers are large enough for this motor. I would have used a 125 amp breaker for this particular motor.
Look at everything you did to this motor and this motor circuit only.

The motor should be drawing much less current that it did on 240 volts. About 1/2 the current.
Check the rewired connections in the motor peckerhead. Sounds like you got this wired wrong.
You did open the peckerhead and connect for high voltage instead of the low voltage connections? (have you smelled or seen any smoke?)
How about the motor nameplate information. Take a picture and post it.

ps..isolate the other motors and only start the 40 HP motor and see.
The main will see all the current with all connected and running.
You are protecting the 40 hp with its own breaker right?
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Last edited by John Valdes; 03-11-2018 at 08:49 PM.
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Old 03-12-2018, 09:21 AM   #10
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wouldn't be the first time wiring to an item that vibrates worked perfectly fine until someone touched it. It's worth ringing out the conductors from the starter to the peckerhead to ground (and each other) in case there's a wire scuffed in the conduit, and again from the motor leads to the motor case in case something's scuffed at the bushing going through the motor housing. It's also worth sticking your screwdriver in the fan end to see that the driven load spins freely. Since this is a voltage conversion, my guess is that the machine was recently moved, so anything could happen.
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Last edited by MDShunk; 03-12-2018 at 09:25 AM.
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Old 03-13-2018, 08:43 AM   #11
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Since my original post I've been made aware of more information. The owner of this company that I was trying to change the machine from 240 to 480. Is only running 10 welding machines, a sandblaster, a washer, a powder coat booth, and the dry off. all from the same two hundred amp breaker. Plus the power that was run for my panel is spliced. Lucky for me my general manager has taken over
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Old 03-13-2018, 08:47 AM   #12
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As a side note the machinery I listed uses a manual conveyor system and this plant builds cattle and horse trailers. Just to give a comparison to the machinery.
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Old 03-13-2018, 09:21 AM   #13
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It's funny how things start to make sense when you get all the information huh?
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