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120V AC motor grunts and trembles on forward, but does not rotate.

My milling/drilling machine motor runs on reverse only. On forward it makes a bad noise and trembles. It is a 120V AC, 1ph, 1.5HP, 1700 RPM. The switch has 3 positions: forward, off, reverse. The motor has a box with two objects about the same size (object 1: JKD Starting Capacitor 400uF, 165V) (object 2: Dianz CBB60 MKPSH 40uF +-5%b). The motor has an internal centrifugal switch. I have checked thoroughly for anything blocking movement (including the gear box guts) without finding anything. I do not know much about electricity. This problem has grown from sporadic permanent. The whole thing is a year old. If I do the following: run normally on reverse, turn switch to off and, just before stopping, move to forward, the motor continues runing normally, but on reverse. Nice, but that is not what I want. The manual does not indicate that this motor could run on 220V, which was a suggestion on a somehow related issue on the forum. Unfortunately drill bits do not make holes on reverse, so I would appreciate some ideas.

Reply to
correcaminos
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Single phase induction motors, the most likely kind you have, will ordinarily run in the direction started. To get them started in the desired direction, capacitors are often used to start them in the desired direction. Once started, they will continue to run in that direction even after the starting capacitor is removed.

My guess is that your forward start capacitor is bad. Unfortunately, there are are many detailed variations in how such motors get started. If you can DO SO SAFELY, put the switch into the forward position and start the motor manually in the forward direction. If it then speeds up in the forward direction, that will prove that the trouble is with your starting setup.

Bill

If you

-- Ferme le Bush

Reply to
Salmon Egg

I would guess the big cap is for start and is switched out by the centrifugal switch and the small one is a run cap that stays connected.

I presume the switch, in addtion to applying power, connects the start winding in one direction for forward and reverses the leads for reverse (or could be the start winding in series with the caps). My Ouija board says that switch is not making both connections anymore to the start winding in the forward direction. The switch is making connections to the main winding when in the forward direction as evidenced by the motor continuing to run (in reverse). So check that all the switch contacts are closing in the forward position.

bud--

Reply to
Bud--

Thank you Salmon Egg and Bud.

This morning I cleaned the contacts after my wife told me last night that it was the switch, even though she knows nothing (I mean nothing) about mechanics or electricity. She gets a few of these strange revelations that are uttered with absolute certainty and turn out to be right; just like your Ouija, Bud. The thing is working great now; however, it was not easy to put the switch back together (6 springs pushing 12 filthy (burned) contacts on 6 different position saddles, sliding on 6 different wheels). If somebody, like me (with a 3 over 10 in electricity), wants to try this surgery, I recommend keeping the most strict order of positions and using a marker to identify each piece and its orientation. Of couse, disconnect the main power, wear safety glasses.

Gracias.

Correcaminos

Reply to
correcaminos

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