Engery consumption of 15HP motor - 1PH vs. 3 PH 1

[LDutch]

Hello everyone, I'm a civil engineer who needs a little help. This may be a very dumb question, but here goes. If my client has his choice between a 1PH or 3PH motor, both 15HP which would run the exact same piece of equipment, is there a "better" choice as far as which motor would cost more for energy consumption.

Thanks for the help!

 

[Mobius44]

The motor energy consumption also varies with the actual motor selection, so why not check the motor data yourself rather than ask us to guessimate which motor's you're buying? All the major motor suppliers offer motor data online, just compare efficiencies.

I have a couple other tips that might help you:

If energy consumption is a primary criteria then you'll want to evaluate a high-efficiency motor.

Consider comparing total cost of ownership, not just energy consumption. Most 15HP 1PH motor designs include start switches and capacitors that will cause more downtime and cost more to maintain than 15HP 3PH motor designs.

-Sean

 

[jraef]

Cost of the installation might be slightly higher for the 1 phase motors as well. It will have a higher FLC (Full Load Current) and will therefore require larger conductors. 1 1 phase 15HP motor (assuming 240V 1 phase) will have an FLC rating of around 73A, requiring conductors capable of handling at least 90A; whereas a 15HP 230V 3 phase motor will have an FLC rating of around 42A, requiring conductors capable of carrying 53A. That represents a signiicant difference in conductor size and cost (albeit the 3 phase motor needs 1 more conductor). From that standpoint then, also go for as high a 3 phase voltage as you have available at the site. In other words if they have 480V 3 phase, use that because the FLC drops to 21A.

If they only have 208V 3 phase, then the cable cost difference will be negligible, but the efficiency may be worse, because if you can even find a 15HP 1 phase motor (they are not common), they will typically be designed for 230V and ACCEPTABLE to run on 208V, but the efficiency will be less than at 230V..


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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[itsmoked]

Going over about 5HP in single phase is often a poor idea for numerous reasons.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

I agree with itsmoked. If you have three phase available don't even consider single phase for 15 Hp.
If your supply is 120:208 Volts, you will want a 200 Volt rated motor in North America.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

NONE of the FLA charts for 1 phase motors list anything above 10HP, so when I was looking for data to get the FLA I had to search manufacturer's data. I found a few out there so someone must use them, but they were not at all common. The only one I found that provided data on FLA was Baldor.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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[itsmoked]

It's going to be 3X the size of a 3ph. It's going to probably cost 2 or 3x more. It will need three men and a boy to move it.

It will hit the power system like a Hefty Bag filled with lasagna hits the pavement after a hundred floor drop.

I have a 5HP TEFC running a compressor. It's relatively new and it's gigantic.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[fangas]

I agree with all of the above. Especially, Smoked's

Incidentially, ignoring all losses, 15 Hp. = 11.19 kW.

It doesn't matter, 1-Ph, 3-Ph, or DC.

3-Ph will be easier to install,maintain, and is more rugged for an industrial environment.

Ed

 

[edison123]

What is the speed required ? 3 ph motors come in only specified synchrpnous speeds like 3600/3000 RPM, 1800/1500 RPM, 1200/1000 RPM etc. for 60/50 Hz.

Having said that, 3-ph motors are preferred at that HP.

Muthu

http://www.edison.co.in

 

[jraef]

It will hit the power system like a Hefty Bag filled with lasagna hits the pavement after a hundred floor drop.

Love the imagery... but why put lasagna in a hefty bag?


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376