Capacitor start motor help please

Another possibility is that it is improperly wired. It happened to me once. Check the diagram.

Most all of the hand grinders I've seen have brushes. If that is the case, your armature is probably a little dirty or the brushes are hanging up in the holders.

If you are talking about a pedistal grinder, make sure it is hooked up for the proper voltage. A cap could be the problem depending on the type of motor.

John

Is it an induction motor or a brush motor?

On Mon, 10 Oct 2005 09:29:06 -0500, "Robert Swinney" wrote: Greetings Bob, The motor is a capacitor start induction motor. Are there brush motors with capacitors? Eric

Yes, electrolytic start caps can dry out. Easy to check, they're cheap. Yes, if the cap were weak it would start slowly, and draw a lot of current while struggling up to speed.

As someone else suggested, make sure you're applying the right voltage.

I have a 6" Heavy Duty Baldor grinder that recently started to run hot then gently waft out smoke. I flipped it upside down, replaced the start cap with an identical one..and it still does it.

What could be the cause? Bearings are free wheeling of course. It starts slow..and runs slow.

Do I need a rewind? (Cringe)

I dont think there is a start switch inside, though Ive not pulled the bells.

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

It has the correct voltage. The motor is not a dual voltage motor. There is only one correct way to wire it and it is wired that way. It may be that if the end bells were removed there would be wires that could be changed for 220 but the paperwork states that it is a 120 volt grinder. Once up to speed it has plenty of torque. It just takes a long time to get there. I'll try a new cap. Eric ERS

yes, then try a new cap, they cost next to nothing.

There are capacitor run motors with no start switch, but most cap start motors do have a start switch. Run caps are different from start caps.

If it's an electrolytic start cap, there is a start switch. Used to be that run caps were in metal cans, but there are plastic-cased ones now.

Try disconnecting the cap when the motor is running. If it runs happily then, chances are you have a stuck start switch.

Some grinders, like the little Baldor you own (that came from me) are not capacitor start squirrel cage motors, rather they are split-phase motors with a run cap permanently in the circuit. These can take longer to start, and often I used to give a wheel a little spin just before I flicked the switch.

Those will start more slowly the bigger the inertial load they see. In other words, if yours starts a lot faster with no wheels on it, then slows down when you put max size wheels on it, it might be a PSC motor.

GWE

Start caps are electrolytic, and they are inexpensive. Many small grinders aren't capacitor start motors, they're split phase motors with permanent run caps in the circuit. Those can easily cost $50. Ouch.

GWE

check ebay... they sell these run caps much cheaper than that...

Grant, I'm brain dead. Must be. I just read a couple months ago for the fourth or fifth time a book about electric motors. And of course it's a cap run motor. If it was a cap start it would still have a centrifigul switch. I have some run caps hanging around. I'll swap one and see what happens. Eric

Ill do just that.

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

Sure the new cap wasn't shorted ? Shorted it drives the coil only and would be slow starting without the kick. Does it have a switch ? working ? The cap if functional - bet that is it!!! - cap is ok - switch is shorted. Then it is in start mode all of the time with extra kick current and overheats - runs slow due to copper heating and perhaps excessive flux.

Bet the switch is the real issue. The start/run on the rotor one.

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder

Gunner Asch wrote:

What??

A specially sized cap to fit in a restricted space in a tool, custom made for the tool manufacturer, maybe. But you can always buy a generic cap for testing before dropping big bucks on a guess.

I just bought some generic 10 Mfd 450V electrolytic run caps - the round was $4, the oval were $4.50. And that was without shopping, I just dropped into Johnstone and said "I Need 'Em."

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Over the years a number of people have asked (and answered) that question here.

I see where Scientific American shows the process in their August 05 edition in the Working Knowledge article.

DOC

Buy my junk!

Any photos of the "machine" for checking the balls? IIRC, it's just a series of anvils the balls bounce across after going down a ramp. The ones that make it across pass, the ones that fall off are rejects. I've heard about these things, but I've never seen a photo.