Duel voltage AC drive???

Is there such an animal?

We are rebuilding a peice of construction equipment that will move from job to job (inside well/caisson rotary drill rig). It has a 3HP duel voltage motor w/a reversing contactor. Different jobs have different power supplies (3phase 208, 220 & 460), and I was hoping for a "fits-all solution" rather then switching drives per job.

BTW it will be an open loop applicaiton.

Thanks, Mike.

Hey Mike,

Rather than changing drives, how about installing two transformers (460 x 208 and 220 x 208, each with individual primary and secondary contactors and then design your controls such that you sample the connected supply voltage and energize the appropriate contactors?

I haven't spent any time thinking this through so there may be some safety/operational issues, but what-the-hey...

Steve

I was thinking along similar lines but suggest an autotransformer with 3 sets of connections for the 3 different voltage requirements giving 480 output to the drive. What will be the method of connecting the equipment up when on site - plugs/sockets or wired to terminals ?

I would suggest you select the voltage you will most likely to encounter. Then have a transformer that can step up or down to suit. You might be able to locate the transformer close enough to the source to not worry about class restrictions. You build a small skid that can be easily moved and positioned out of the way.

Saves having to rewire the motor every time too.

I havent thought about it all that much either, and was hoping to stumble upon a drive that could deal with it. We have a couple of local tranformer shops, Dungan & Power Tran. Right now I'll set it up for 220 and look into the transformer for step down.

Still open for ideas. Thanks for the replys.

Mike

I have no personal experience with autotransformers so I can't comment on the use of one, but I do wonder about using a step-up transformer to go from 208 to 460 as compared with a low voltage drive and a step-down transformer. It strikes me that, dollar-for-dollar, the step-up transformer would be less efficient than the low voltage drive.

I have never heard of an on-the-fly type dual voltage drive, though.

Steve

Steve,

I would choose the low voltage setup & use a step down just because the lower potential would present less hazard. Power supplied to the unit will be a large extension cord.

Another reason for stepping down and using the lower voltage drive is that if someone does happen to misconnect the power you will just be undervoltage at the drive. OTOH, if you were stepping up and someone misconnected the power (say they connected 460 to the 230 tap) then you would have a very dangerous situation.

Higher voltage drives cost much less than lower voltage drives. A 230VAC Drive requires twice the current for the equivilant HP at 460, and since the power stack is usually the costliest part of a drive, I'd standardize on 460.

Autotransformers are just plain evil. I'd stay away from them except in the rare case that you need a cheep buck/boost configuration to say go from 208 to 230VAC.

Mike, just my thoughts from working in an industry that moved machinery all the time.

I would consider, since all you mentioned was a 3HP motor, is using 230/240v single phase in 3PH out drive.

Use a single phase transformer from 480 to 230/240.
Use a single phase transformer from 208 to 230/240.

Have 3 input receptacles on the machine, one connects thourgh the 480 transformer, one throught the 208 step-up, and the other supplies staright 230/240 to the machine.

This method "assumes" that those using and connecting the machine know what they are doing but some failsafes could be added if necessary. This also removes any need to make changes to the drive.

The "extension cord" would need to be SO type cable but this method would allow the use of a 3 wire cable no larger than 12ga, maybe 10ga if there are other power requirements OR the cable may have to run long distances.

I thought about multiple drives but there is the aspect of control voltages etc, if incoming voltage changes then what you use for that will probably need to change.

I would probably still have a disconnect switch and possibly a voltage display, if the voltage reading is not 230 then do not turn on the machine.

I like rsdoran's solution but I dont' think a 208/230 transformer is worth the trouble. the only point where a 208V input would affect the output of a 230V drive is at maximum speed. The voltage would level off at around 56Hz and the motor would be a bit voltage-starved about that. Unless your load is right at motor nameplate, you will never notice the difference.

Ok, I'm with Dick & Ron. 1phase in 3phase out drive (may run into some sites with just single phase) & 460-230 step down transformer for lower voltage projects.

Ron, the rig will be setup & run by elevator journeymen, so proper hook-up shouldnt be a problem.

This thing starts, stops, and reverses frequently. The guys were complaining about the single speed, and constantly servicing the contactors etc... Long over due for an upgrade.

Ok, We need a watertight/Washdown rated dongle. So who makes a good 8 button dongle? E-Stop, Fast, Med, Slow, Fwd, Rev, & Up & Down. I plan on using 24vdc controls on the dongle, as this type of operation is often use with slurry.

By dongle do you mean like a pendant?, do you want wired or wireless?

PENDANT!! That's it! I couldnt think of the proper term. "Brain Freeze"

Thanks allscot.

The reason i stated use 2 transformers is due to control voltages, I know drives can handle different voltages but to mainatin a specific control voltage you need transformers.

I can not find the link for Woods weather proof pendants, maybe you can now that you know the name.