can i reduce new motor start up speed


Old 07-26-15, 09:38 AM
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can i reduce new motor start up speed

i bought a used ridgid table saw with a bad 1 1/2 hp 3450 rpm emerson motor made in usa, i bought a harborfreight 1 1/2 hp 3600 rpm electric motor to replace it and have it wired for 240 volts. the new motor runs fine however it seems to start up to fast as the 6v serpentine belt squeals only at initial start up. is there any way i can reduce the start up rpms maybe by changing the start up capacitor. the previous emerson motor was wired for 120 volts. i am guessing if i can change the capaciter i can reduce start up speed or i was thinking on changing the serpentine pulley to a 2 or 3v standard pulley like on my previous grizzly 3hp 240 cabinet saw. i do want to fix the emerson motor, will be another thread. pic of hf motor name plate.
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Old 07-26-15, 11:13 AM
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can i reduce new motor start up speed
Not easily or inexpensively.

Changing the start capacitor will not do what you want.
You would need a VFD (variable frequency drive) unit to electronically change the speed. They are available from many places and I've bought several off of eBay.


Single Phase VFD: Drives & Amplifiers | eBay
Old 07-26-15, 05:52 PM
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3600 rpm is synchronous speed on a 60 Hertz power supply so that motor does NOT attain that speed, more likely it doesn't even make 3500 rpm under load.

Changing to standard vee belt drive is probably the easiest. Serpentine belts require a lot of tension to keep them from squealing at start up or sudden load application.
Old 07-28-15, 09:27 AM
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the two serpentine pulleys are 2" diameter x 5/8". i am going to buy a double v pulley and that should make everything better. this ridged table saw i bought for $100.00 as it is about a $600.00 table saw. as long as i don't spend to much money i got a good deal on it. this table saw has an all cast iron top, the new ones are part cast iron with stamped steel wings right and left side, they got cheap on quality. thanks very much for the help and suggestions.
Old 07-29-15, 08:13 AM
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the harborfreight store electric motor had a 3450 rpm rating on one motor on display then on a new box it said 3600 rpm.
Old 07-29-15, 08:53 AM
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It is essentially the same thing. 3600 RPM is the "perfect" speed for a 2 pole motor with no load and ideal lubrication. Under typical operating load installed in a machine the same motor should run approximately 3450 RPM. The difference between the ideal and the loaded RPM is called the "slip" of a motor, and roughly correlates to the motor's torque. 3450 RPM motors are pretty much the industry standard for shop machinery like saws, planers, etc.

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