I wonder if the motor was miswired or miswound when it was manufactured, and that's why it looks like it has had very little use.
I wonder if the motor was miswired or miswound when it was manufactured, and that's why it looks like it has had very little use.
In reply to Pete. (l33t FS) :
It's possible. I'm finding capacitors for $12, so that's cheap enough I'll give it a shot.
11GTCS said:In reply to Curtis73 (Forum Supporter) :
Any voltage rating equal to or greater than the 125V specified will work as long as it has the 400 mfd rating. So yes, a 240 V / 400 mfd cap would work just fine as would one rated for 277 or 480 V.
Good to know, thanks. Makes me wonder why they would use a 125v in a motor that has instructions on how to switch between 120v and 240v.
In reply to Curtis73 (Forum Supporter) :
Maybe someone DID hook it up to 240 and blew it up? 
Exiting smartass mode, depending on how the start winding is wired the cap may not be seeing the full 240 V even if the motor is wired to run that way.
It's currently (pun intended) wired for 220v. Both the owner's manual and the J-box have diagrams for wiring it both 120v or 240v. The plate on the motor also lists amperage for both 120v and 240v. It's definitely a dual-voltage appliance, but just curious why they used a 120v cap.
Ok, one more question.
I ordered a new cap and it should be here tomorrow. I didn't notice any markings on the old cap that would indicate polarity, and I was reading that some types of caps it matters, others it doesn't.
How do I know?
This is the cap I ordered: https://www.amazon.com/dp/B01MUHSY23?ref=ppx_yo2ov_dt_b_fed_asin_title
In reply to Curtis73 (Forum Supporter) :
AC doesn't have a polarity - current flows in one direction then the other.
In reply to RichardNZ :
I'm aware of that, but I wasn't sure if it mattered. Thank you
Well, the new capacitor didn't change anything.
I suppose I have nothing to lose by tearing the motor apart, although I don't know what I'm looking for. About all I've done with electric motors is replace bearings and brushes.
Tore it apart today and found nothing. No burned windings, bearings are great, centrifugal switch looks brand new. I blew out a little dust.
I took the points off the centrifugal switch and gave them a scuff with a nail file, but they looked fine. I put it all back together and added a 10-ga pigtail which is overkill, but I was thinking maybe the 12-ga it came with was too wimpy.
Same exact thing. Resistance across the two lines was (and still is) 0.7 ohms. I was watching a video where the guy was working with a 1/4 hp motor and his ohmed out to 7 or 8, but he said that the bigger the motor, the less there should be. How many ohms should I be seeing on this 1.5hp?
Edit: Wait... Resistance is voltage/amperage. So 220V/8A is 27.5. Is that a valid thing to expect to see, or does the amperage change when the field is excited?
Okeydokey.
In order to detect bad windings, you need a megaohm meter called a "Megger" in the industrial electrician sphere.
As opposed to standard meters, meggers run higher voltage and measure higher resistance.
Does the motor have a nameplate? Does it list full load amps (FLA) for 120V and 240V? Otherwise you can use a NEMA chart to get close.
The table above is the max sustained amps a motor should be pulling once it is up to speed and loaded up. Free running should be less, maybe about 1/3 of nameplate amps in this application.
Inrush current will be higher, can be 3-4 times full load amps, but it should settle down after a few seconds as the motor reaches full speed. When the motor is full speed/no load, it should be running 1/2 to 1/3 nameplate amps just as a ballpark number for you.
If this motor is sustained over 100A draw and you have confirmed it is wired correctly, all the wires are in good shape, etc, then its really leaning toward the motor is bad.
Other thought is that the breaker is weak/tired or has too long of a run with undersized wiring to support this amp load. Have you tried other outlets or going straight off the breaker on a short pigtail?
93gsxturbo said:Okeydokey.
In order to detect bad windings, you need a megaohm meter called a "Megger" in the industrial electrician sphere.
As opposed to standard meters, meggers run higher voltage and measure higher resistance.
Does the motor have a nameplate? Does it list full load amps (FLA) for 120V and 240V? Otherwise you can use a NEMA chart to get close.
The table above is the max sustained amps a motor should be pulling once it is up to speed and loaded up. Free running should be less, maybe about 1/3 of nameplate amps in this application.
Inrush current will be higher, can be 3-4 times full load amps, but it should settle down after a few seconds as the motor reaches full speed. When the motor is full speed/no load, it should be running 1/2 to 1/3 nameplate amps just as a ballpark number for you.
If this motor is sustained over 100A draw and you have confirmed it is wired correctly, all the wires are in good shape, etc, then its really leaning toward the motor is bad.
Other thought is that the breaker is weak/tired or has too long of a run with undersized wiring to support this amp load. Have you tried other outlets or going straight off the breaker on a short pigtail?
Nameplate just says "Grizzly." Same as the rest of the saw. Also says made in Taiwan, so I'm sure it's whatever third party came in with the lowest bid that quarter. No listing of FLA, just 16A @ 120v and 8A @ 220v. So even if startup amperage were quadruple, that's 32A. Assuming my ammeter is accurate, I'm drawing 4 times that even after startup.
The breaker is working fine on my Delta table saw, and also runs my 225A welder at full song. Since the motor is drawing 119A, I don't think I can fault the breaker. Just for giggles I plugged the saw into my 60A outlet for the powdercoating oven, and it still tripped.
I'm starting to think it's a bad motor as well. About all it could be is a shorted winding, yes? Wires all looked good, and it now has about 6' of 10/3 SJO and a brand new 6-50 plug.
Thanks for all the help. I'll start shopping for a motor. I'm sure having this one rebuilt would cost more than just buying one.
In reply to Curtis73 (Forum Supporter) :
Sometimes there can be what's called a spot burn in the windings that will result in a dead short. The windings on these motors are copper wire with only a thin coating of "varnish" (probably some type of epoxy now) keeping the copper from touching. A small flaw in that coating can cause a failure, depending on where it is you may not be able to see it although you can usually smell it when the motor is energized. I've seen similar things happen with imported or off brand 3 phase motors on commercial equipment. If it is shorted you should be able to read it with a common multi meter either from leg to leg or to ground depending on how the motor failed. (dead short = 0 ohms whereas a winding would have a definite reading ( 20 ohms for example).
In reply to 11GTCS :
Good to know.
I found a replacement online for $127. I'm sure I couldn't get it rewound for that much.
I was getting 0.7 ohms leg to leg. That explains the 119A I suppose.
Curtis73 (Forum Supporter) said:Edit: Wait... Resistance is voltage/amperage. So 220V/8A is 27.5. Is that a valid thing to expect to see, or does the amperage change when the field is excited?
Resistance plays a part but in an AC circuit Impedance is what you are dealing with. Pulled from Wikipedia - In addition to resistance as seen in DC circuits, impedance in AC circuits includes the effects of the induction of voltages in conductors by the magnetic fields (inductance), and the electrostatic storage of charge induced by voltages between conductors (capacitance). The impedance caused by these two effects is collectively referred to as reactance and forms the imaginary part of complex impedance whereas resistance forms the real part.
You won't be able measure impedance directly so don't worry about it, resistance is the right thing to measure but like others have stated a Megger is the tool to do this properly. They run at 500-1000V typically, a good winding would have that voltage stable and give a resistance reading to ground, a bad one (which yours likely is) would have the voltage collapse (go to OV) and a very low resistance reading.
I'm not sure what the resistance of your windings should be but 0.7 ohms is probably too low, I'd be curious to know what resistance your meter reads when you just put the two leads directly together as that might give a 0.7 ohm reading as well (or close to it) telling you the winding is actually shorted.
Motors can be rewound and there likely is a motor shop in your area that could do it, this motor likely isn't worth it if you can find a suitable replacement.
In reply to adam525i :
My meter (Fluke) reads an actual 0.0 when I touch the leads together.
Thanks for the very valuable description.
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