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EnviroStart - Motor Energy Controls


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#1 belza

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Posted 22 February 2006 - 08:19 AM

Hello Marke,

Thanks for the quick reply and concern.

Envirostart is claiming that there motor energy controls can save up to 40% of energy. How would it be possible for envirostart's to realize a significant saving for single phase induction motor driven loads such as refrigeration and airconditioning units (rated at 220V) considering the actual supply voltage available from the electric company is only 215V or 218V? Does envirostart mean that their motor energy controllers are capable of constantly tracking the voltage and current so as to keep their phase displacement as small as possible during the entire duty cycle, thereby providing a higher power factor and thus the efficiency?

#2 marke

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Posted 22 February 2006 - 09:09 AM

Hello belza

Yes, it is possible to save 40% of the power consumed, but this would be on a totally unloaded motor. As the load ins added to the motor shaft, the power saved reduces (both in % and in KW)

The important figure to consider, is not the % saved, but the KW saved as that is what you pay for.

The circuit reduces the voltage applied to the motor and by so doing, reduces the iron loss in the motor. There will be a reduction in the magnetising current with the reducing voltage. This will reduce the flux in the iron and that will reduce the iron losses. If the motor is under no load, the current drawn will be essentially magnetising current only, so there will be a reduction in the measured current and copper loss.
If there is any shaft load, the work component of the current will increase with the reducing voltage, increasing the copper loss.

If the motor is operating with reasonable shaft load, do not expect to make much if any savings, often, reducing the voltage at part load will often result in an energy loss.

The best applications for this technology, are machines that spend a considerable amount of time operating under no load conditions. Machines such as plastic granulators and punch presses are good candidates. Machines operating continuously at say 60% will not yield the savings quoted except possibly where the motor is considerably over fluxed.

The only way to be sure, is to try a unit and see. Make sure that you measure the power consumed with a proper power meter. Do not fall into the trap of meauring voltage and current on the output and multiplying them together. You must use a kw meter.

Best regards,

#3 belza

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Posted 22 February 2006 - 10:18 AM

Hi Marke,

Yeah I agree with you.

In fact I've already theoretically examined based on an actual 10hp motor design that the power factor correlates the efficiency. This encourages me further to try construct the power saver which was introduced by NASA, and see its action.

Anybody from the viewer who is interested, or have experienced in the working capabilities of the power saver by NASA?

#4 marke

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Posted 22 February 2006 - 05:48 PM

Hello belza

I would expect that the 10HP motor will be a three phase motor rather than a single phase motor.
It is a lot more dificult to get a three phase system operating correctly than a single phase system.
Additionally, the three phase motor is a lot more efficient and so will yield much lower results than a small (fractional HP) single phase motor.

The energy that you will save is a portion of the iron loss only.
If you take an induction motor, find out the full load efficiency, you can determine the toatl losses at full load.
The iron loss is essentially constant, independent of load and is in the order of 30 - 50% of the full load losses.
In the case of a 10HP motor, I would expect to see an efficiency of perhaps 90% or higher at full load. Therefore the losses at full load could be as high as 0.833KW. The iron loss may be in the order of 0.4KW and so at light load, you may save up to 200 watts. As the load increases, the percentage of the iron loss that you can save reduces and by the time that the shaft load is up to 40%, you will not have any savings at all in most cases.
Under open shaft conditions, you may save 50% of the energy consumed, but 50% of 500 watts is not a great deal. In the order of 3.5% of the motor rating under open shaft conditions and reducing as the motor load increases.

If you wish to get some advantage from the technology, use the single phase motor and only small ones.


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Best regards,




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