Understanding motor voltage rating vs. machine voltage rating

[paulbr]

Need help in finding appropriate paragraphs in NEC or other regulatory documents.
We are building machine, which is designed and labeled for three phase 208VAC electric power supply. One of the components on the machine is a pump. Nameplate on the motor of this pump is showing only 230/460 Volt, but not 208 Volt. In the past pump manufacturer was providing motor nameplate with 208-230/460V rating. When, we asked them to provide new motor nameplate, answer was that they have switched to premium efficiency motors, which are rated 230/460V.
Is it OK to use component that is rated higher than voltage of the circuit, where it will operate. Paragraph 110.4 saying that it "shall be not less than nominal voltage". Nothing is said about opposite. During testing measured motor current is higher than one shown on motor nameplate, 37.3A vs. 34A. Motor service factor is 1.00. Based on nameplate information motor load is 110%.
My feeling is that if machine as whole rated for 208 volts, then each component must have this rating. Can anyone point me to appropriate regulatory documents on these matters.
Thank you,

PaulBr.

 

[Jraef]

Your motor supplier has done you wrong, you need to switch. If the nameplate no longer says it is good for 208V, then it is a 110.3B violation. The equipment is not suitable for the intended use. If you put two different voltages on the nameplate you will confuse your customers, then they will call us, and we will tell them to change out the motor or add a buck-boost transformer.

If the motor were rated for 1.15SF and you were using it at 1.0, I might be inclined to let it slide. But you have the opposite situation, a 1.0SF motor that ends up at 110%, that too is a 110.3B violation.

You (your company) are the customer for the pump, tell them to meet the spec or you will find another supplier who will.

 

[SSDriver]

Also check the rating plate at the very bottom. I have seen multiple motors where the voltage lists 230/460. BUT then at the very bottom says something similar to "usable at 208 volts". In words.

Edit: see picture

 

[paulbr]

Thank you, Jraef for code clarifications.
Thank you, SSDriver for the suggestion. I've checked motor nameplate. It does stipulate using at 208V, but motor current is missing at this voltage. Will get back to pump and motor manufacturer with request to update motor nameplate.

 

[SSDriver]

Let us know what the manufacturer says.

My calculations from the name plate

746x15= 11190 watts
11190÷208÷1.732÷.91÷.91= 37.5 amps at 208 volts.(unless they use utilization volts at 200 for calculations).

for reference
746x15= 11190 watts.

11190÷230÷1.732÷.91÷.91= 33.92 amps or 34 amps at 230 volts

 

[retirede]

Ideally, a NEMA motor will have a 200V nameplate voltage for use on 208V systems.

 

[SSDriver]

Ideally, a NEMA motor will have a 200V nameplate voltage for use on 208V systems.

That is what i see when it is a single voltage motor. Ifs its only for 208v I see a 200 volt name plate. Ifs its multiple voltages I always see 208-230. I have no idea why.

 

[retirede]

That is what i see when it is a single voltage motor. Ifs its only for 208v I see a 200 volt name plate. Ifs its multiple voltages I always see 208-230. I have no idea why.

View attachment 2564188View attachment 2564190

It’s because they take a 230/460 motor and label it for tri-voltage. There is no unique 208V winding configuration. Quite often, there will be a footnote to the effect that the 1.15 service factor doesn’t apply at 208. Regardless, the life of the motor running on 208 will be less than if it was running on 230, all else being equal.

 

[Jraef]

That is what i see when it is a single voltage motor. Ifs its only for 208v I see a 200 volt name plate. Ifs its multiple voltages I always see 208-230. I have no idea why.

A Baldor engineer once explained to me that they start with a 220V design, then add more steel to the stator so that it can handle +-15% without being damaged by over heating. So at 220V - 15% it is good for 187V, which is 208V - 10%, and 220 + 15% = 253V, which is 230V +10%.

A 200V motor for a true 208V installation is 200V +- 10%, so good down to 180V, that way if your motor is large and likely to CAUSE a significant VD on a 208V system, it's better to use a 200V rated motor. That's why you won't see the "tri-voltage" rated motors beyond a certain size. I think for Baldor, it was 10HP as the cut off.

 

[retirede]

A Baldor engineer once explained to me that they start with a 220V design, then add more steel to the stator so that it can handle +-15% without being damaged by over heating. So at 220V - 15% it is good for 187V, which is 208V - 10%, and 220 + 15% = 253V, which is 230V +10%.

A 200V motor for a true 208V installation is 200V +- 10%, so good down to 180V, that way if your motor is large and likely to CAUSE a significant VD on a 208V system, it's better to use a 200V rated motor. That's why you won't see the "tri-voltage" rated motors beyond a certain size. I think for Baldor, it was 10HP as the cut off.

Back on the 1980s when tri-voltage first became a thing, we tested them. Our equipment was sized at 110% of nameplate HP.
The only manufacturer’s motor that would hold up was Toshiba.
At the time Toshiba was too expensive so we simply didn’t use tri-voltage motors. We wouldn’t even put them on a 240V machine so no one would be tempted to use them on a 208V system.