Baldor 12 wire motor

This is aimed at the American members. I have a 12 wire motor wired for 230V. The supply to the VFD is 230V three phase. Our standard supply here is 380V three phase. I would like to standadise my drives, we only use 380v three phase drives. My question is, can I wire my motors to run on 380V three phase? See the attached picture of motor connections

briancr said:

I have a 12 wire motor wired for 230V. The supply to the VFD is 230V three phase. Our standard supply here is 380V three phase. I would like to standadise my drives, we only use 380v three phase drives. My question is, can I wire my motors to run on 380V three phase? See the attached picture of motor connections

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I have not worked with 380V three phase. But here in the states we can wire up a motor for 240 volts and set a custom V/Hz curve in the VFD so that the VFD receives 240 volts at 60 hz when the VFD supply is 480 volts. You should be able to do the same. My reason for doing this is not the same as yours though. I do this to get no torque loss above 60 Hz. when I need 120 Hz.

Note: when ever I do this type of thing I leave lots of documentation. Drop tags on the motor pecker head labels on the VFD notes on the prints, and labels on the field disconnects. So that the night shift electrician has lots of reminders that this is a special setup.

Based on this older thread http://www.eng-tips.com/viewthread.cfm?qid=131777&page=1 it looks like you can wire the motor for 460V/60Hz and run it at 380V/50Hz without much loss in torque. From my very basic understanding of this, looks like you'll get 5/6 of the rated torque out of the motor that way.

A motor wired for 460V 60hz operating on 380V 50hz will develop its full torque but at 5/6 speed. Thus, the kw or hp is reduced by 5/6.

DickDV said:

A motor wired for 460V 60hz operating on 380V 50hz will develop its full torque but at 5/6 speed. Thus, the kw or hp is reduced by 5/6.

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Just to give you more info to back up DickDV
In South Africa I suspect you use Weg or Teco motors as we do in NZ ,
if you look at the name plates on the motors you will see details for that motor if used on 50 or 60 Hz giving the differences in Kw Voltage and Current have a look at the ratios.

If you are using VFD, you may configure you output voltage to be 230V at max frequency (make sure your motor's isolation is suitable for 550VAC - VFD DC bus voltage). If no VFD - you may wire a motor for 460VAC. But you have to consider some power reduction.

Guys, Thanks for the replies, very interesting reading.

It is an American built machine, so it is a 60Hz motor, using two 11KW motors driving a single shaft. Unfortunately for me, my starting torque is high, so a loss of 5/6 will be a problem.

It looks like I have two options:
1. Stay with a three phase 220V drive - but @ Milldrone, here is a problem with night shift guys, even with labels all over, I know I will get a 2am call saying the drive is smoking. makes me think of a new fun thread, keep an eye out for it.
2. Change my motors to 380V 50 HZ rating, probably a more expensive route, but a much safer route.

Once again guys, very good information passed over, it's almost beer time here for me

Briancr, did you read my post? Especially the part about torque?

DickDV said:

Briancr, did you read my post? Especially the part about torque?

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sorry DickDV, i did, but i misinterpretted it, so basically all I need to do is wire it for 460V and up my max frequancy on the drive to get my desired speed. I normally do run at max rated motor speed

milldrone said:

I have not worked with 380V three phase. But here in the states we can wire up a motor for 240 volts and set a custom V/Hz curve in the VFD so that the VFD receives 240 volts at 60 hz when the VFD supply is 480 volts. You should be able to do the same. My reason for doing this is not the same as yours though. I do this to get no torque loss above 60 Hz. when I need 120 Hz.

Note: when ever I do this type of thing I leave lots of documentation. Drop tags on the motor pecker head labels on the VFD notes on the prints, and labels on the field disconnects. So that the night shift electrician has lots of reminders that this is a special setup.

Click to expand...

What is the torque loss like when you go below 60? Just to much to learn yet. Dang.

Tom@Pton said:

What is the torque loss like when you go below 60? Just to much to learn yet. Dang.

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Tom,

In a normal VFD setup ie. 480V input to the VFD and the motor connected in the peckerhead for 480V. There is no loss of torque until you rise above 60 hz. In these normal setups the VFD supplies the motor with 240V at 30 hz and 480 V at 60 Hz. The problem is the motor is under voltaged above 60 Hz. A ratio of 8 volts to the Hz needs to be maintained when the motor is connected in the pecker head for 480 volts, if not a decrease in output torque is experienced. If DickDV responds he might explain further in more detail.

I work in an industry that is evolving and trying to be more efficient than the next guy. We are always trying to get more out of our machines. VFD's play an important role in this endeavor. I'm going to describe two very different ways two apply VFD's to a motor.

Management wants a process to run faster (than previous) on certain products and slower (than previous) on others. Research is done to determine if gearboxes, bearings and other mechanical drive components are up to the task. If they are not, then changes are made so it is safe to operate under the new conditions.

1. The classic motor in my industry to apply a VFD to is a feed motor. One of the upgrades commonly applied is to install a larger motor and gearbox. The strange thing is that quite often the gear setup is to drive the machine slightly slower at 60Hz than it did previously. The way we get the extra feed speed desired is to raise the Hz above 60 to about 90 Hz. In this setup the VFD is supplied with 480 V and the motor is connected in the peckerhead for 480 V. There is some loss of torque above 60 Hz but this made up for by the gearing change and the larger motor. Another benefit of this gearing change is that we get a larger speed range, classically 20 to 90 Hz. as opposed to 20 to 60 Hz.

2. Sometimes it is determined that a particular motor has the capacity to run at 120 Hz but we need the motor's full torque at that speed. So this time the approach is to connect the wires in the pecker head for 240 V and supply the VFD with 480 volts. A custom V/Hz curve is programmed into the VFD. When the motor is connected for 240 V it needs 4 V to the HZ to operate correctly (.as opposed to 8 V to the Hz when connected for 480 V) If this method is applied it is very, very important that all of the electricians know this so that if a motor is changed out it is connected correctly or if a VFD is changed that it is programmed correctly. I should mention that the VFD needs to be sized for the full load amperage of the motor when it is connected for 240 V.

Thank you,

I have been an electrician for about 35 years, dabbled in PLCs with some success for 15, and only in the last 5 have had much to do with drives. I find this application very interesting. My customers could very well have benifited had I the knowledge and guts to try it.

The key to understanding the ability of an induction motor to develop torque is to see that available torque is directly related to the volts per hz ratio. So, with that in mind, 460V/60hz, 380V/50hz, and 230V/30hz will all give you the same available torque. The speed will vary with the hz but the available torque will hold constant. In very good sensorless vector or flux vector drives, this relationship holds all the way down to zero speed with the motor producing full nameplate torque at zero speed as a holding brake.

What Milldrone is describing is a very crafty way to get more from a motor by using the low voltage winding in a dual winding motor. Connected for 230V/60hz you get nameplate torque at 230V/60hz. But, since the motor insulation is capable of 460V, you can cheat the system by increasing the 230V/60hz all the way up to 460V/120hz (note the constant V/hz ratio) and the motor will develop full torque up to double speed thereby doubling the available horsepower. As long as the motor bearings and balance are ok at double speed, you're good to go.

Just a note. I wouldn't recommend going to double speed on two pole motors without careful analysis of the mechanical integrity of the rotating elements. But, on four, six, and more poles, this can be done generally without much concern below about 250hp.

What about Motors that are 480 and have a 120HZ or 90 HZ rating on the nameplate?

Do you lose torque when you run those at 120HZ?

My bakery has 2 100 HP motors like that.

Tim Ganz said:

What about Motors that are 480 and have a 120HZ or 90 HZ rating on the nameplate?

Do you lose torque when you run those at 120HZ?

My bakery has 2 100 HP motors like that.

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Are those frequency ratings for Base Frequency or Maximum?