4x6 Motor is Working!

[deltaenterprizes]

My A/C repairman suggested taking my motor to a local repair shop to see if it needed a centrifugal switch.
I bought it in on Friday and got a call today that it ran but is drawing full load amps without any load.
Any ideas as to what could be causing this?

[BCRider]

Probably the same issue as Mikey's motor as detailed in the other thread?

They are the motor experts. They should be telling YOU!

[ahidley]

Yea, the centrifical switch isnt working or you have a bad capicator

[chipmaker4130]

It isn't all that uncommon to see high apparent amps/no load on a typical induction motor. Has something to do with the voltage/current phasing and isn't really what it appears to be. J Tiers here can explain it, I can't. Whether this is what they're seeing with your motor is still a question.

[mikey553]

My A/C repairman suggested taking my motor to a local repair shop to see if it needed a centrifugal switch.
I bought it in on Friday and got a call today that it ran but is drawing full load amps without any load.
Any ideas as to what could be causing this?

You did not tell us what is wrong with your motor. A few pictures would help too.

[mikey553]

I did not realize you are talking about your new Grizzly motor. We need the details.

[wmgeorge]

Confused, what motor and its at the motor shop and they don't know?

[wmgeorge]

Yea, the centrifical switch isnt working or you have a bad capicator

Its at the motor shop..... they should be telling Him!

[RMinMN]

I suggest you use more words and tell us what motor, its HP rating, the rated voltage and amps, type of motor, and the symptoms you have that caused you to take it to the motor shop. Then maybe we can make the right kind of guesses.

[I make chips]

Go easy RM, He might be ESL.

[J Tiers]

I don't know of any motor that pulls current equal to the full load amps when running unloaded. I suppose it is possible, but it would be a pretty crummy design for most purposes. About 40% of full load current is reasonable.

Any motor shop should be able to find the usual suspects, like wrong connections, bad centrifugal switch, possibly a shorted turn, etc, etc. And should be able to fix them.

It isn't all that uncommon to see high apparent amps/no load on a typical induction motor. Has something to do with the voltage/current phasing and isn't really what it appears to be. J Tiers here can explain it, I can't. Whether this is what they're seeing with your motor is still a question.

That does happen normally, but not usually with full load amps.

Quick explanation:..... "Power" is volts x amps. That can be measured by any reasonably accurate meter for DC, or when the voltage and current are "in phase" (both at maximum at the same time).

If the voltage and current are "out of phase", the current may be maximum when the voltage is lower than maximum, perhaps much lower. Then, the amps as measured on a simple meter cannot be just multiplied by the voltage. The number from simple multiplication is called "apparent power" (or "VA", meaning "volt amps"), but is not necessarily "actual power". You have to account for the fact that the current occurs at a lower voltage, meaning that the "actual power" is lower.

In that case, the meter has to multiply the "actual" volts at each instant, by the "actual" current at the same instant, to get the true power.

Motors have "inductance". When you apply voltage to an inductor, the current rises somewhat slowly. That delays the maximum current, and causes current and voltage to be out of phase (current is "delayed", usually called "lagging current").

So the motor usually, when unloaded, will pull about 40% of full load current. But because that current is "lagging", the actual "power" used is much less than you may think. It may be only 10% to 15% of the "apparent power".

There are terms used such as "imaginary current", etc, but you don't need to consider that. All the current is real enough, and can be measured. The term "imaginary" means something else in this context, just don't get hung up on it.

[BCRider]

This is a follow on to his EARLIER THREAD. It got a bit sidelined by Mikey and his similar saw and potentially similar motor issue.

[chipmaker4130]

Thanks, Jerry. Makes sense to read it.

[mikey553]

Come on Delta, tell us the whole story. The more details - the better it is. A few pictures would not hurt either.

This is a complicated issue, at least for us, mechanical people. To make matters worse I encountered another single phase capacitor start motor with heavy no load current. This time it is a reputable old Dayton 1/3 HP motor. I am still testing it and will report when I am done.

For my 4 x 6 band saw I elected to go 3 phase since I have a 240 V receptacle nearby. New 1/3 HP WEG motor from Ebay costed me $53 total. New 1 HP Mitsubishi VFD was $112 total including sales tax. Together that is about the same as Delta paid for his new 1 phase capacitor start Grizzly motor. But in my case I've got a brand name motor and VFD and hopefully there will be no issues. I already have a VFD on my mill and I love it. There is no real need for a 3 phase on a band saw, but I like such complications and speed adjustment on the fly would not hurt either. Should receive the motor and VFD in a few days and will play with them a little on the bench before installing on the saw.

[deltaenterprizes]

The original motor is back on the saw and is working!
The motor shop found nothing wrong with the original motor so I put it back on.
I canceled the Grizzly motor because a friend has a Dayton 1/3 HP 1725 rpm capacitor start new in the box, but it is not TEFC.
Members here related that they have used open frame motors with no problems so I will have one as a spare.
I am not sure of the quality of the Grizzly motor and would rather take a chance on the open frame and put a shield by it.