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Power Factor Correction Using Synchronous Motor.


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#1 Milind

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Posted 09 November 2006 - 04:21 PM

Hi ! I am Milind

If a plant has a fairly big ( > 2 MW ) syn. motor , how can use it to improve the overall power factor of the plant ? What data should I ask the motor manufaturer for this purpose?

Thank a lot.


#2 jraef

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Posted 09 November 2006 - 11:10 PM

By adjusting the field strength in the synchronous motor rotor, you can move the motor's power factor from lagging to leading. Since all of your other asynchronous induction motors are going to have lagging power factor, you can use the synch. motor in leading mode to provide the reactive power (VARs) for them. This is referred to as using the synch. motor as a "Synchronous Condenser" and is a very common practice when you have a large load that will run continuously.

Because power factor penalties can be very expensive, some people even go so far as to run Synchronous Condensers without a load on them at all! If that were the case, you would need to maximize your investment by making sure that your synch. motor was big enough to supply enough VARS of reactive power to make it worth while. In your case since the motor is connected to a load you may not want to do that, but it is worth looking into. Other than that, there really isn't anything that you need to tell the motor supplier. If the controller is part of his package, make sure it allows you to make that adjustment. Even if you are going to do the control system yourself, make sure that feature is included. One simple way is to use a packaged controller such as a GE/Multilin SPM unit on the controller. It has the ability to automatically make the motor provide VARs by monitoring an analog input, say from a plant-wide PF transducer.
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