Compressor 3 phase 230/460 volts

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Fordean

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Electrical Contractor
They ordered a compressor, It was ordered at 230 volts.

I have 208 maybe slightly lower. I know the 10 percent rule. But the Manufacture said 208 is to low. I believe it will be fine. ??
 
Gosh, what would the manufacturer know about their equipment :)
Easily correctable with a buck-boost transformer.
 
Fordean said:
They ordered a compressor, It was ordered at 230 volts.

I have 208 maybe slightly lower. I know the 10 percent rule. But the Manufacture said 208 is to low. I believe it will be fine. ??
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I would look at the actual motor data plate or data sheet. Some motors will say "230v" in say the catalog, but say 208-240 on the motor itself or data sheet. Some will specifically say do not use at 208.
 
Industrial air compressors are routinely sized at 110% of motor nameplate horsepower at full load. That basically uses up 10 of the 15% service factor of the motor. That service factor is what makes a motor wound for 230V operate on 208V with reasonable life.

Depending on the application, you might be fine, but you’ll not get an OK from the manufacturer.
 
If you have only 208-volt service in the building, cancel the order and re-order a compressor with a 200-volt motor.
I can't think of a good reason for a new installation to be installed wrong.

Boost transformers and autotransformers are kludges that will waste energy.
Running a 230-volt motor on 208 is a kludge that will waste energy, might void the warranty, and probably will raise the operating temperature and reduce longevity.
 
drcampbell said:
If you have only 208-volt service in the building, cancel the order and re-order a compressor with a 200-volt motor.
I can't think of a good reason for a new installation to be installed wrong.

Boost transformers and autotransformers are kludges that will waste energy.
Running a 230-volt motor on 208 is a kludge that will waste energy, might void the warranty, and probably will raise the operating temperature and reduce longevity.
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Can you calculate the energy loss of two 2 KVA BB transformers that operate 12 hours a day 6 days a week, 50 weeks for us? Fill in the blanks that are needed. I chose 2 KVA at random.
 
2160 kW·hr per year, plus whatever magnetizing power is used 24/7 to keep them warm, if they're wired upstream of the contactor. About half the amount of electricity my entire household consumes, for this one motor alone. Plus demand charges, which are usually attached to 3-phase services.
 
ptonsparky said:
Can you calculate the energy loss of two 2 KVA BB transformers that operate 12 hours a day 6 days a week, 50 weeks for us? Fill in the blanks that are needed. I chose 2 KVA at random.
Click to expand...
drcampbell said:
2160 kW·hr per year, plus whatever magnetizing power is used 24/7 to keep them warm, if they're wired upstream of the contactor. About half the amount of electricity my entire household consumes, for this one motor alone. Plus demand charges, which are usually attached to 3-phase services.
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Never seen that question or answer before.

Who would have thunk it.

Not us knuckleheads
 
Even if the nameplate says it can run at 208 V in addition to 230 V or 460 V, it does not mean that that motor will operate at the specified efficiency or power factor. It just means it will run. The so-called "triple-rated" motors are not warranted to perform equally at 208 V and 230 V. Adding an autotransformer is a last resort to be used in an emergency. Whoever screwed up the order should fix it by replacing the motor. Especially since the manufacturer says it won't work.
 
What kind of compressor?
How many HP?
Reciprocating, screw compressor?
Across line starting, VFD, soft starter?
Is there a control transformer or is controls same as supply voltage?
 
ptonsparky said:
Can you calculate the energy loss of two 2 KVA BB transformers that operate 12 hours a day 6 days a week, 50 weeks for us? Fill in the blanks that are needed. I chose 2 KVA at random.
Click to expand...

Assuming a pair of 2 KVA transformers to take 208V to 230V. This gives a load current of 75A, somewhere in the 25 or 30 Hp range.

Figure the transformers will have 5% core loss, running 24x7. So I estimate 200W * 8766 hours = 1750 kWh just to have the transformers present.

Figure the transformers will have another 10% copper loss when the load is on. So 400W * 12 * 6 * 50 = 400W * 3600 hours = 1440 kWh of losses when the transformers are loaded.

The load itself is assumed to be 24 kW, so 24 * 3600 = 86400 of real consumption.

So tacking the buck-boost transformer on adds 3.7% to energy use.

More realistically, the compressor won't be running full time during a shift. So the 1440 kWh of copper loss and the 86400 kWh of consumption both go down proportionally with run time. But the core loss is constant unless you put the transformers downstream of the control contactor (meaning the contactor has to deal with transformer inrush and higher current, not a good idea). Say the compressor runs 30% of the time...that core loss factor has now jumped to nearly a 7% energy use adder.

So IMHO the additional losses to using buck/boost transformers with the 'wrong' compressor are not huge in a relative sense, but also not insignificant.

-Jon
 
augie47 said:
Gosh, what would the manufacturer know about their equipment :)
Easily correctable with a buck-boost transformer.
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How would you continue. Please be detailed

Thank You Can you attached a model number. I can't return the unit they ordered it a while back. Why would they make 230 volts Its dual rated at 230 /460 but wired at the 230. Most know 208v are in the buildings. It this more European designed? Like to know why a 230 volt available. Mechanics order this stuff with no knowledge of power available. Motor say 7.5 HP 230volts 20 amps
 
Fordean said:
How would you continue. Please be detailed

Thank You Can you attached a model number. I can't return the unit they ordered it a while back. Why would they make 230 volts Its dual rated at 230 /460 but wired at the 230. Most know 208v are in the buildings. It this more European designed? Like to know why a 230 volt available. Mechanics order this stuff with no knowledge of power available. Motor say 7.5 HP 230volts 20 amps
Click to expand...
This is almost a disposable. Use it as is and replace the motor if and when it fails. I suspect a good number of years.
 
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