skydiver Posted November 3, 2010 Report Share Posted November 3, 2010 The equation for calculating synchronous speed is: S = 120 f/P speed = constant (120) times frequency of power source (60 Hz) divided by number of poles used in the motor (P). Where does the 120 come from and what units does it have? There is RPM on one side and Cycles/second divided by #of poles on the other. Does the constant contain units to make both sides the same? I have not found this explained anywhere else. Does it involve conversion from seconds to minutes and cycles to revolutions? Thanks for any help you can give. Link to comment Share on other sites More sharing options...

yuri Posted November 4, 2010 Report Share Posted November 4, 2010 Rotation is measured in number of rotation per minute. So 60 sec multiplied by 50 Hz for instance divided by number of pairs of poles - 1 pair for instance - gives synchronous speed 3000rpm. In your case there was meant number of actual poles - not their paires - actually 2 , the number by which dividend should be multiplied automatically, so instead of 60*50/1 one have 2*60*50/2 or 120*50/2. So I always thought, hope it helps. Link to comment Share on other sites More sharing options...

skydiver Posted November 5, 2010 Author Report Share Posted November 5, 2010 Rotation is measured in number of rotation per minute. So 60 sec multiplied by 50 Hz for instance divided by number of pairs of poles - 1 pair for instance - gives synchronous speed 3000rpm. In your case there was meant number of actual poles - not their paires - actually 2 , the number by which dividend should be multiplied automatically, so instead of 60*50/1 one have 2*60*50/2 or 120*50/2. So I always thought, hope it helps. This makes sense and validates the equation if I just use UNITS on each side without numbers. Thanks Link to comment Share on other sites More sharing options...

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