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4 Pole Motor Instead Of 6 Poles - The Torque Issues

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#1 AB2005


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Posted 28 May 2014 - 04:31 AM



In a flexo printing machine, we are going to upgrade its folding belts system for which, after final calculations, we are required a 3phase 5KW 950rpm motor to provide 600rpm at driven side. A question raises here that what happen if we select a 5KW 1450rpm motor (instead of 5KW 950rpm) and reduce the speed at driven side by reducing the teeth of chain sprockets. Would there be same torque in both cases? This is why that normally 6poles motors are rarely available in our local market while 4poles are easily available. There is no any issue of space for sprockets and motors.

"Don't assume any thing, always check/ask and clear yourself".

#2 marke


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Posted 28 May 2014 - 05:07 AM

Hello AB2005


If you use a mechanical speed changing mechanism such as a belt drive, chain drive or gearbox to change the speed, then, ignoring losses, the power output will equal the power output. Power = Torque times speed, so as you reduce the output shaft speed, the torque will increase. This is exactly the same as reducing the speed of an induction motor by increasing the number of poles.


So in answer to your question, provided that the speed changing system has a high efficiency, then the result will be the same.

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