Frequency Drive Motor Contoller

Laredo7mm

Laredo7mm

Joined
Jul 8, 2002
Messages
1,240
I have a 2 HP 3 Phase motor that drives my grinder. I think if I lower the speed of my grinder when using the finer grit belts, I can have better control of my hollow grind. Right now she runs at 6000 sfpm.

I have found a used ABB variable speed motor controller, but it does not exactly match my equiptment. the controller's input is 380/440V 3 Phase. My input would be 230V 3 phase. The rated output amperage is lower than what i would need, but if I can run it on 230V instead of 380V, then the output current should drop right into the range i need.

Would it still work, or should i shop arround some more?
 
Laredo, I haven't seen one that voltage before, but my experience has been that VSD's have problems with low voltage.We use ours at 230 volts ,but a drop to 208 volts causes a big drop in output power.If your voltage goes much below 200 volts the VSD will usually trip.However if the price is right you can always get a step-up transformer from 230-440 volts.Hope this helps.Dave:)
 
I wouldn't try running anything electrical on 1/2 the specified voltage source. Your motor speed controller could be comprimised by doing so and so could your expensive grinder.

Motor speed controls and such things as light dimmers adjust the duty cycle of there output in order to slow or dim. The output voltage is consistent and it is the amount of time relative to a cycle (hertz)that the voltage is output that causes motors to change in speed. This is because they (in this case the grinder) are only on part of the time even though all the time they are on they are getting a full dose of their specified operating voltage.

An argument to motor speed control might be a devise commonly called a Variac (an auto transformer - Variac is a trade name). The auto transformer actually lowers and raises the output voltage relative to source voltage. It can achieve aprox. 140 volts of output with 110 volts of input.

Roger
 
Laredo

If the ABB drive has been designed to allow operation from a 230V supply, it's output current rating will most likely be LOWER than what it would be with its normal 380V-480V supply, which you say is already too low. This is the case with the motor drives that are made where I work. Please do not think of a motor drive like a transformer, they don't work that way.

Check your motor to see how the windings are connected and what the current rating is. If they are connected in a Delta configuration now, you can reconnect them in a Star configuration to make it run on 400V. If the motor nameplate only gives you the current rating at 230V, you can compute the equivalent current rating at 400V by dividing the number by 1.73. Check to see if the 400V current rating of the motor is within your drives rating at 380V - 480V. If it is, you would then have to acquiring a 3-phase auto-transformer to step up from the 230V to 400V, or so.

If you are going to do any of what has just been described, get the assistance of a qualified electrician who has industrial experience, not just residential experience. Otherwise, you may seriously injure yourself.

If you are going to use the drive, make sure that you get a copy of the manual for it so that you can set it up correctly. With the proper settings, your motor should run very smootly. The previous user may have put in really wierd settings for his application that may cause you a lot of grief in the form of rough running. You may have to go to your local ABB dealer to get a manual.

If you cannot use the drive but got it a really good price, you may want to keep it for some other lower power application. Quite a few of my co-workers have prototype drives or other old units in their home shops.

The Applications Engineers here at work caution that if the motor is not rated to work with a drive, it may suffer premature failure if run in a hot environment while connected to a drive.

If you want a more detailed explanation on the above, e-mail me directly at pso@nz.schneider-electric.com

Best of luck

Phil
 
I say: thumbs up! on VFDs.

I recently put one on my big vertical band saw. Mine is single phase 220V input with 220V 3ph out. I used an old motor that I had laying around...no special invertor duty thingy. In comparison, invertors have more to offer than DC drives. They can be programmed to protect your motor. They also offer a wider speed range in the sense that you can over speed the motor from its base speed. For example, I run my 1725 rpm motor as fast as 4000rpm with the invertor. I wouldn't be suprised if the motor comes apart at that speed ...so we'll see. I have more motors in case. The invertors also can be programmed for dynamic beaking, current control, acceleration, reversing....and more. They can be configured for constant torque or constant HP. Mine has absolutely no problem running slow. The LED screen lets me visually monitor all sorts of functions as well. For example, at any given time, I can look over to see how much current the motor is drawing.

So Laredo, to answer you question....yes! invertors will work very nicely on your grinder....Unless you got a deal on the ABB, I would shop a bit. I'd look into a single phase input, 3ph out model so you can free up your phase convertor. I bought an Omron/Yaskawa 2hp unit for about $280 from a local motor shop. Campared to DC drives, they can be very intimidating to install and setup. The manual for the VFD is about 200 pages of technomumbojumbo....compared to 60 pages for a Leeson DC drive. But you'll have no problems and probably will welcome the technology.

That's my 2 cents.

Good luck and keep us posted. Guys are always looking for Variable speed solutions for their machinery...let us know what you do.

Sincerely,
Rob
 
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