Old vs new motors

[jim king]

We are running 40 year old motors and some possibly more.  The electric bill is growing out of proportion to other costs.

Would anyone know the savings by switching to new efficient motors ?

We have headrigs with 100 hp,  14 , 20 hp motors on the kilns , and a varity of 10 hp and others.  The power is 220.

I would appreciate knowing if it is worth changing to new motors as I have read.  There doesnt seem to be much info available or more likley I dont know where to look.

[Chuck White]

I would suggest that you contact a company that sells new motors and get their cost savings comparisson.

Although not as big a scale as the power you use, early this spring we got a new refrigerator, freezer and water pump for our home.
We were sceptical about any savings on our electric bill, but we routinely save between $40.00 & $50.00 a month on our utility bill!

New should cost less to operate!

Chuck

[jim king]

Chuck:

We dont have anyone selling motors here and no one with knoweledge on this.  We are in the upper Amazon hundreds of miles from the nearest road.

[Gary_C]

I think much of the efficiency savings with the more efficient motors comes from downsizing the motor frame, mass, and windings. The downside is you give up reserve capacity and heat disapating ability. Many of those old motors had service factors of 1.25 meaning they could handle 25 percent more than nameplate capacity.

You would have to get the numbers together to find out if it would pay. One way to make an estimate is by comparing the max current rating on the nameplate with a newer more efficient motor of the same HP. In order to get closer numbers you would have to get actual running amps and idle amps plus know the run times for each. It's possible you could save by getting smaller motors that could still run the equipment. But the only way to know is to get actual numbers.

Just offhand I would guess the savings would be marginal. You could probably save more by turning things off when not needed. In other words don't leave motors idling any more than you have to.

[Norm]

What kind of power source do you have? The biggest savings will be to use true 3 phase voltage to 3 phase motors.  Matching the size of motor to it's duty will help also.

[StorminN]

Hi Jim, our utility here encourages us to use a motor database to find new more efficient motors, and to calculate savings... I'm at home and don't have my work bookmarks, but I think this is the link:

http://www.motorsanddrives.com/
http://www.motorsmatter.org/

-Norm.

[Celeriac]

You might want to check out www.weg.net, they have a calculator tool to help with figuring cost and savings on motors.  Being as they're headquartered in Brazil they may well distribute to your area. 

[Mr Mom]

Could you make your own power?? Might be easer to get a generator.
just asking.

Thanks Alot Mr Mom

[sparky]

Here is a General electric website with a calculator to show the savings that could be gained by changing to a more energy efficient motor:

http://www.gemotors.com.br/calculator/

Where I worked before retirement, we had an aggressive program to install premium efficiency motors where they were justified. If a motor is quite old as is the case with this question, and has been rewound a few times, the efficiency suffers because the performance degrades with each trip thru the burnout oven prior to rewinding. The new, premium efficiency motors have much higher efficiencies than the old motors.

Motors in the 100 HP class can have efficiencies of 94%. An older motor may be as low as 85% efficient. One of the considerations is the rate per kilowatt-hour that is being paid for electricity. Another is the run time per year. These are part of the GE calculator program.

Sparky

[StorminN]

Jim, you might also look at your rate structure... how you are billed for your electricity. I know at our factory, our power company (a public utility district) bills us for three things... the kWh used, the power factor and the instantaneous peak demand... they measure the demand usage in 15 minute chunks.

The kWh are of course, simple... the longer a motor is on, the more kWh it uses.

The power factor is nothing we can effect, unless we were to switch to new motors with better power factors.

BUT... the peak demand we can change... what this means is, if someone comes in to the factory at 5am and turns on all the motors at once, we have a huge surge of power used within one 15 minute period. This is recorded by our meter (digital), and we pay a penalty for this (last time I checked, in our case, it adds up to about $1,000 a month, a bit less than a third of our bill). If, however someone were to come in a turn on one big motor, then wait 15 minutes and turn on another big motor, then another 15 minutes and another big motor, we would have to pay much less for our power. Getting people organized to do this in our shop is near impossible.

It all really depends on your utility and how you are billed. Some utilities also bill for time-of-day usage, so you should check on that, too... (not that you're going to mill in the middle of the night, but there might be some way to shift some things)

-Norm.

[schmism]

3phase and higher voltage should gain you some efficiency.  (more current = more heat = loss)  for 10 and 20hp 440 should be common.

i would even look at 600V for the 100hp

[sparky]

You might avoid a small amount of losses in the feeders to your large motors by increasing the supply voltage, but you would experience greater loses in the transformer that would provide the higher voltage. You had indicated that you are receiving 220 volt power from your electrical supplier. I would stay with 220 volts unless there is an extremely long feed to you mill. There are calculations that can be made to determine the amount of line loss you might expect in your feeder cables.

My thoughts on the subject,
Sparky