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???
08/31/09 05:38
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 		 #168637 - Now I know why...
Responding to: ???'s previous message
Per Westermark said:

Another thing is that the motor is optimized for a specific frequency. The motor doesn't just have a DC resistance. It also has an inductance, and the iron in it has a limited capacity to store magnetic energy. If you reduce the frequency it will run slower. But each half-period will have more time to charge magnetic energy. So you have to be prepared to reduce the amplitude of the signal at the same time as you are reducing the frequency.


AN984 of Microchip also says that if we have to run the motor at a different speed than what it is rated for, then we have to change the frequency AND the amplitude...now I know why, thanks for your post.

List of 29 messages in thread
TopicAuthorDate
AC Motor question            01/01/70 00:00      
   with these questions            01/01/70 00:00      
   More questions            01/01/70 00:00      
      not neccessarily            01/01/70 00:00      
         May be, but...            01/01/70 00:00      
            inverters have a potentiometer input            01/01/70 00:00      
   Replies to Erik and Daniel            01/01/70 00:00      
      go ahead and then cost it            01/01/70 00:00      
         Thanks Erik            01/01/70 00:00      
   Dear Suttar            01/01/70 00:00      
      STAY AWAY            01/01/70 00:00      
         It doesn't have to be so bad if you switch at zero crossing            01/01/70 00:00      
            and give tyhe AC motor every other cycle ????            01/01/70 00:00      
               No ... just turn it on and off at zero crossing            01/01/70 00:00      
                  it is an AC motor, details, details, detalis            01/01/70 00:00      
                     Horrible motor control            01/01/70 00:00      
                     Who said anything about removing cycles?            01/01/70 00:00      
                        on and off at zero crossing....            01/01/70 00:00      
                           and if you cut only half cycles ....            01/01/70 00:00      
                              Nope ... it just happens at power-on and power-off            01/01/70 00:00      
                                 that is NOT what this thread is about            01/01/70 00:00      
                           Only when you turn the motor on or off            01/01/70 00:00      
         To Erik,            01/01/70 00:00      
            Slip            01/01/70 00:00      
               "inverter certified" motors ...            01/01/70 00:00      
            Creating new sine wave at different frequency            01/01/70 00:00      
               Now I know why...            01/01/70 00:00      
            no, the frequency generated by the inverter            01/01/70 00:00      
      Reply to Vu Nhu Khanh            01/01/70 00:00      

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