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Thread: 240v electric motor
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3rd Sep 2018, 10:49 AM #1
240v electric motor
This motor was off the bench saw project which i scrap. $20
Resize of IMG_6592.jpgResize of IMG_6591.jpg
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3rd Sep 2018, 12:53 PM #2
I’ll take it, subject to HP and pick up location.
Cheers.…..Live a Quiet Life & Work with your Hands
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3rd Sep 2018, 01:07 PM #3
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3rd Sep 2018, 02:45 PM #4Member: Blue and white apron brigade
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5A @ 240V = 1200W -20% for efficiencies = 1080W = ~1.5HP
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3rd Sep 2018, 10:50 PM #5Senior Member
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Bob, I would be surprised if the motor shown is more than 1HP. I think your assumption of 20% losses for inefficiencies is being rather conservative, given the class of motor and the fact that it is four pole. On the practical side I have a similar CP 1.5HP motor which is rated at 7.1 amps. I would expect a similar four pole motor to draw 7.5 to 8 amps.
Chas.
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3rd Sep 2018, 11:29 PM #6Member: Blue and white apron brigade
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You are right my calc above is wrong
It should be 5A @ 240V = 1200W -20% for efficiencies = 960W = ~1.29 HP
Working backwards from your motor 240V @7.1A = 1.7kW = 2.28HP rated at 1.5HP = 65% efficient which is on the low side, more like a low class 1/2 HP motor. I've measured the actual HP and efficiencies of a few 4 pole motors (including some relatively elderly ones) around the 1kW output level at the rated current and never seen one with that low an efficiency.
The usual efficiency I measure is around 80% which is consistent with this chart.
Screen Shot 2018-09-03 at 8.07.40 pm.png
My experience is that HP output ratings printed on motors are fairly nominal - and on small motors often stated to the nearest and higher 1/2 HP. interestingly none of the cheap chinese motors I have measured have output less than their stated HP.
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4th Sep 2018, 07:26 AM #7Senior Member
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4th Sep 2018, 10:01 AM #8Member: Blue and white apron brigade
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