Voltage lag

A new air compressor was installed, and it requires no less than 208 "Y" 3 phase volt.
The main service was tested at 199 to 201 "Y" 3 phase. just that lag in voltage is causing problems with the air compressor.

Question: What is the best way to increase the "Y" 3 phase voltage up 8+ more volts.

Thanks,
Brian
:blink:
 

retirede

Senior Member
Location
Illinois
Missed the edit time.

Another thought - does the compressor have a tri-voltage motor? If so, I could see 200V at the supply causing problems.
 

GoldDigger

Moderator
Staff member
The best (most economical) way to increase the wye supply by 8V per leg would be to use three independent boost transformers, one on each leg.
It is technically more difficult to use a boost transformer to raise the voltage of a delta supply.
 

Besoeker

Senior Member
Location
UK
The best (most economical) way to increase the wye supply by 8V per leg would be to use three independent boost transformers, one on each leg.
It is technically more difficult to use a boost transformer to raise the voltage of a delta supply.
Or raise the primary taps?
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
“Lag” has to do with time. You have a low voltage. But unfortunately for you, it is not lower than 95% of nominal, so it’s unlikely that the utility (PG&E?) is going to address it for you. Did you ask though? That’s the easiest fix.

Besides adding the boost transformers mentioned earlier, another option is to replace the motor with a version that can live with your service. Most likely you have a 230V motor which, at -10% makes it good for 207V input, hence their statement of “no less than 208V” (with a little hedging). The aforementioned “tri-voltage” motor would say on the nameplate that it is “208-230/460V” and give you three different FLA values for the three voltages. In those motors, the windings are ok with 208 -5%*, so can accept down to 198.5V input and would be fine for you. But you didn’t state the HP size and tri-voltage motors are typically limited to lower HPs (10HP and below). If your motor is 50HP or something like that, you will have to use a specifically labeled 200V motor.

Here is an older post on this subject rather that repeat it all. http://forums.mikeholt.com/showthread.php?t=168338&p=1636355#post1636355

* Technically they say -10%, but then go on to say it will run hotter and have a shorter life, so I use -5%
 
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