solution to soft start an ac induction motor

[jackorocko]

Just as the title of the thread ask, I am wondering what type of solutions I have for soft starting a 120v ac induction motor with starter coil and capacitor start? It is a 1HP. This is on a lathe so I would like to stick to 120V to avoid any extra external electronic motor controllers needed to control the direction of rotation with a drum switch.

 

[duke37]

I have used a resistor, shorted out with a relay after about a second.
The resistor needs to be a few ohms and many watts.
The timing can be done with a rectifier, resistor and capacitor.

I do not see how this will work with a direction switch, perhaps a current transformer could be used to reset the relay.

 

[jackorocko]

I had the same thought using a resistor. I was really hoping they made something like a soft start capacitor, but as you say changing direction causes an issue because it would work in one direction and be totally negated in the opposite direction.

Oh well, seems I might have to bide my time until I can stumble upon a 3 phase motor.

 

[Y2KEDDIE]

Running on 220VAC is allways better if you can.

If you can find a 1 HP three phase motor; MC Master Carr carries a nice little electronic converter.page 869, Catalog 116: Three Phase AC Motor Speeed Controller. This unit is small, 4.5" x 6.9" x 4.4". Its variable and has reversing.

 

[Externet]

Commect a 120VAC light bulb in series with the 120VAC motor.

The lower the bulb wattage, the lower the motor speed. Want more speed, choose a larger wattage bulb.
Relays or switches bringing the bulb(s) into/out the circuit can do a pretty and simple speed controlling.