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Single-phase application of the power saver


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#1 belza

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Posted 24 February 2006 - 11:53 AM

Hello Marke,

Yeah the 10hp motor was a three-phase one. I only used its data in extending the analysis of how the efficiency respond to the power factor by varying the resistance that represents the mechanical load in the rotor.

I believe that the power saver is most effective for single-phase applications for the primary reason that these machines are notoriously more inefficient than there three-phase equivalent.

Do you have profitable experience in applying the power saver to single-phase motor driven refrigerators and airconditioners?

#2 marke

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Posted 24 February 2006 - 07:53 PM

Hello belza

Small refridgeration compressors do not operate with varying load, they are either running or they are not. While they are not the most efficient motors, they are operating close to their rated load and are operating near their maximum efficiency. Reducing the voltage in most cases, will not reduce the energy consumed. The beat applications are applications where the motors run continuously with the load cycling. Small punch presses have the motor driving a flywheel with a clutch operating to engage the punching action. Most of the time, the motor is just spinning the flywheel and doing no work.
I have not found refridgerators and air conditionaer to be good candidates.

Best regards,

#3 jraef

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Posted 24 February 2006 - 10:33 PM

I agree. Older refrigerators sometimes had a single motor that drove both the compressor and fan, with the compressor on a clutch so that it only engaged when it was needed, but the fan would run for a lot longer. Those systems are gone now, with the compressor motors being hermetically sealed units that are cycled on and off, and when on they are fully loaded. I sometime think the "study" subjects mentioned in the sales literature for these things were these older non-existent systems.

The machines in Bowling Alleys that reset the pins were good candidates years ago. They would have one motor running a drive shaft continuously that covered 5 or 6 lanes. When pins needed to be reset in one lane, a clutch at that lane engaged to operate the machine for a few minutes. The majority of the time the motor was running idle. Nola units worked great for that. Once the market was saturated however, there were not a lot of other applications to be found. New Bowling Pin Re-setters now have integrated micro VFDs because they are so cheap and allow unlimited starts and stops with the motors.

I did sell them once to a water district that had to service a wide variety of small wells between 1 and 5HP 220V. To avoid their trucks having to carry multiple motors, they standardized on 5HP motors everywhere. They used the Nola units to make sure that when the 5HP motor was on a well that only needed 1 HP, it didn't waste a lot of energy. That worked out as well.
"He's not dead, he's just pinin' for the fjords!"




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