开云体育

The motor is a split-phase (2-wire) 230VAC, 5 h.p. asynchronous cap-start motor on a commercial compressor driving a 2-stage air pump via V-belt drive.

This motor (#3 in the life of this compressor) replaced one (motor #2, 6 months old) that started to trip the circuit breaker. I measured the current draw and it showed 140A at turn-on and 80A for the few seconds before the breaker tripped. (This is with the drive belt removed.) The motor was not hot; it seemed normally warm to the touch. No unusual noises, although this motor generated some unusually strong vibrations, although the bearings were all without play, the armature turns freely, and the output shaft is not bent.

The compressor pump turns freely (indeed, these Chinese pumps turn more easily as they age), although it makes some piston-slap noise when it starts up until some pressure builds up.

The new motor (#3) is identical make & model as #2 from Grainger industrial supply (A.O. Smith label). Name-plate current is 22.0:

<>

I measured the current of the new motor with a Fluke 85 clamp meter. Measured current is 24.5.

The original motor (#1) was replaced 6 months ago. I don't recall what the current draw of that motor was, but I'm sure I would have noticed excess current draw and at least started asking questions.

Should I be concerned about the excess current draw?

Thanks,
Dave

sounds like a shorted turn




________________________________
From: DaveC <davec2468@...>
To: Electronics101 <Electronics_101@...>
Sent: Tue, January 25, 2011 3:16:07 PM
Subject: [Electronics_101] Motor drawing more current

?
The motor is a split-phase (2-wire) 230VAC, 5 h.p. asynchronous
cap-start motor on a commercial compressor driving a 2-stage air pump
via V-belt drive.

This motor (#3 in the life of this compressor) replaced one (motor
#2, 6 months old) that started to trip the circuit breaker. I
measured the current draw and it showed 140A at turn-on and 80A for
the few seconds before the breaker tripped. (This is with the drive
belt removed.) The motor was not hot; it seemed normally warm to the
touch. No unusual noises, although this motor generated some
unusually strong vibrations, although the bearings were all without
play, the armature turns freely, and the output shaft is not bent.

The compressor pump turns freely (indeed, these Chinese pumps turn
more easily as they age), although it makes some piston-slap noise
when it starts up until some pressure builds up.

The new motor (#3) is identical make & model as #2 from Grainger
industrial supply (A.O. Smith label). Name-plate current is 22.0:

<>

I measured the current of the new motor with a Fluke 85 clamp meter.
Measured current is 24.5.

The original motor (#1) was replaced 6 months ago. I don't recall
what the current draw of that motor was, but I'm sure I would have
noticed excess current draw and at least started asking questions.

Should I be concerned about the excess current draw?

Thanks,
Dave

sounds like a shorted turn

You mean the 24.5A vs. the 22 rated amperage? Or are you talking about the one that failed (drawing 80A when it did so)?

Thanks,
Dave

the failed one
I assume you have measured resistance to ground





________________________________
From: DaveC <davec2468@...>
To: Electronics_101@...
Sent: Tue, January 25, 2011 9:59:36 PM
Subject: Re: [Electronics_101] Motor drawing more current

?

sounds like a shorted turn

You mean the 24.5A vs. the 22 rated amperage? Or are you talking
about the one that failed (drawing 80A when it did so)?

Thanks,
Dave