djn602

I am in the middle of a project where we are bidding out the service upgrade of the winery I work at (I am in maintenance). I am trying to unsterstand and learn so I am hoping some people will weigh in here.

We currently have multiple seperate 277/480Y and 240Delta services. So far two seasoned ECs have bid. One proposes switching us to 120/208Y (fed from a new main distro of 277/480Y) which makes sense to me becasue we have many panels where that high leg is unused. The other EC proposes staying with the Delta. My questions really come from how will our motors do? Some are rated 208/230 some are just rated 230. I understand that all(?) motors are built with a voltage range of +- 10%.

I guess it "all depends" is the motor fully loaded, does the POCO dip in the summer or scale back, is the circuit wiring large enough and not too loaded to abate some voltage drop there.

I, in no way shape or form, what anything to do with killing some expensive motors prematurely.

What do we do?

william1978

Are you a electrician?

djn602

I am a low level maintenance person with the company.

mattsilkwood

It's "an electrician".

djn602

removed

william1978

Ok, I won't forget the n next time.

mattsilkwood

zgozvrm

Usually, when the voltage rating of a motor is designated with a slash (such as "240/480V"), it means that the motor can be re-wired (star or delta) to run on one voltage or the other. If the voltage rating is instead shown with a dash (such as "208-240V"), it means that the motor can run with voltages within that range.

What I suspect you have is motors with nameplate voltage ratings like "208-230/460V" which means that the motor will run in the range of 208-230V when wired for low voltage (delta) or at 460V when wired for high voltage (wye). The +/- 10% factor still applies, meaning that (for low voltage), the motor should be able to run in the range of 187V (208 minus 10%) to 253V (230 plus 10%).

If your motors are actually rated as 208/230V (on the nameplate), with no 460V rating, then it is strictly one voltage or the other. In this case, the motor runs on 208V when wired low volts, and 230V when wired high. You should be able to determine which voltage it's running on by looking at the wiring diagram on the nameplate and comparing to the actual wiring.

If NONE of your motors (or other equipment) is running on 230V, then switching from 240 delta to 208 wye should be okay. This is probably not the case though, since 240V (or 230V) tends to be more common than 208V (especially with motors). Also, if any of your motors are actually rated for 240V (rather than 230V), then the -10% rating only allows for 216V and 208V would not be sufficient, whereas 230V motors would allow for voltages as low as 207V. This is so close to the 10% tolerance, that I wouldn't advise doing it.

In our plant, we run delta panels for motors and other equipment, and wye panels for lighting and controls. That way, we get the voltage we want where we want it.