Author Topic: Small compressors - 1725 or 3450 RPM motors and why?  (Read 348 times)

Offline Packard V8

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Small compressors - 1725 or 3450 RPM motors and why?
« on: September 01, 2017, 10:43:12 AM »
I just picked up a Champion C1 single cylinder compressor pump and was lucky enough to get the original dirty paper with it.  The very complete instruction sheet gives pulley sizes "All data based upon 3450 RPM electric motor as a power source." 

Depending upon what I had available, I've successfully used either, sizing the drive pulley accordingly, but just wondering why Champion would assume 3450 RPM as the preferred type?

jack vines
Jack Vines
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Re: Small compressors - 1725 or 3450 RPM motors and why?
« Reply #1 on: September 01, 2017, 11:41:02 AM »
IIRC most all small portable single-stage electric compressors were run with 3450 rpm motors to increase pump efficiency -- because the pumps had relatively small displacement, and were intermittent use only.  It wasn't until you get into the higher end industrial lines that used larger displacement pumps and two-stage configurations that the motor rpm dropped to support longer life, easier startup, and reduced noise.

Offline Packard V8

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Re: Small compressors - 1725 or 3450 RPM motors and why?
« Reply #2 on: September 01, 2017, 02:07:05 PM »
IIRC most all small portable single-stage electric compressors were run with 3450 rpm motors to increase pump efficiency -- because the pumps had relatively small displacement, and were intermittent use only.  It wasn't until you get into the higher end industrial lines that used larger displacement pumps and two-stage configurations that the motor rpm dropped to support longer life, easier startup, and reduced noise.

Not following this line of logic, as fitted with an appropriately sized drive pulley, the pump RPM is per spec, only the motor RPM is different.

jack vines
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Re: Small compressors - 1725 or 3450 RPM motors and why?
« Reply #3 on: September 01, 2017, 04:38:34 PM »
IIRC most all small portable single-stage electric compressors were run with 3450 rpm motors to increase pump efficiency -- because the pumps had relatively small displacement, and were intermittent use only.  It wasn't until you get into the higher end industrial lines that used larger displacement pumps and two-stage configurations that the motor rpm dropped to support longer life, easier startup, and reduced noise.

Not following this line of logic, as fitted with an appropriately sized drive pulley, the pump RPM is per spec, only the motor RPM is different.

jack vines

Sorry Jack, then I'm not getting what your question is? are you worried about output or just wondering why the spec lists two options? I would assume the higher RPM  motors were/are cheaper and were more readily available.

Offline brslk

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Re: Small compressors - 1725 or 3450 RPM motors and why?
« Reply #4 on: September 01, 2017, 08:26:40 PM »
Wouldn't the electric motor RPM remain the same no matter what the size of the pulley and the RPM of the pump change? Or am I missing something?  headscratch
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Offline kwoswalt99

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Re: Small compressors - 1725 or 3450 RPM motors and why?
« Reply #5 on: September 01, 2017, 08:37:43 PM »
Wouldn't the electric motor RPM remain the same no matter what the size of the pulley and the RPM of the pump change? Or am I missing something?  headscratch

The question is why did they use 3450 rpm motors when 1725 rpm motors are more common.
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Offline slip knot

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Re: Small compressors - 1725 or 3450 RPM motors and why?
« Reply #6 on: September 01, 2017, 09:24:55 PM »
I used to know this scratchhead IIRC it was a HP or FLA/torque thing. Been 40+ yrs since my junior high electrical class.
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Re: Small compressors - 1725 or 3450 RPM motors and why?
« Reply #6 on: September 01, 2017, 09:24:55 PM »

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