Starting Motor Without it's Starter Capacitor

In summary, the motor can be run from a regular wall outlet without the starter capacitor, but there is a high chance of a stall.
  • #1
teroenza
195
5
I found a motor I think is from an old AC unit in the recycle. It is a 1/4 HP, 265V, 1.20A AC motor. I've been looking to make a low-torque sander and was thinking about using this as a a drive motor. I know the starter capacitor is there to provide an initial burst of current to get it up to speed.

My question is, If I was to power it from a regular wall-outlet (120V) without the starter capacitor (didn't find one), and start it by hand-turning it, could this create a dangerous situation where the motor pulls too much current or something? I don't see any big problems, but wanted to ask people with more experience.
 
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  • #2
You have a 265 VAC motor and you need to run it with 265 VAC. The starting capacitor is not there to give it an 'initial burst of current'. It is wired in series with a special starting winding and causes a phase shift in the current in that winding. This causes the appearance of a rotating magnetic field and the rotor follows it. There is a centrifugal switch that opens that starting winding once the rotor is up to speed. It is no longer needed. Typically though, if you rotate the shaft of a an AC induction motor by hand that has no current in the starting winding it will come up to speed whichever way you rotate it.
 
  • #3
teroenza said:
My question is, If I was to power it from a regular wall-outlet (120V) without the starter capacitor
Why don't you calculate a starter capacitor:

http://www.electricneutron.com/electric-motor/single-phase-capacitor-sizing/

and buy one:

http://www.grainger.com/category/capacitors/motor-supplies/motors/ecatalog/N-9yp ?
 
Last edited by a moderator:
  • #4
This is dangerous and is not recommended. I've had times when it was done in a emergency until a proper motor was installed but the chance of a motor stall because of the low power (~25% of normal) and the resultant cooking of the motor is high with no run capacitor.
http://ecmweb.com/design/highs-and-lows-motor-voltage
 

Related to Starting Motor Without it's Starter Capacitor

1. Can a starting motor function without its starter capacitor?

Yes, a starting motor can still function without its starter capacitor, but it may require more power and time to start up.

2. What is the purpose of a starter capacitor in a starting motor?

The starter capacitor provides an extra boost of power to the starting motor, making it easier to start up the motor and reducing the strain on the motor's components.

3. How does a starting motor without its starter capacitor differ from one with a starter capacitor?

A starting motor without its starter capacitor may have a slower start-up time and may require more power to start, whereas one with a starter capacitor will have a faster start-up time and require less power.

4. Can a starting motor be damaged if the starter capacitor is not present?

In most cases, a starting motor will not be damaged if the starter capacitor is not present. However, without the capacitor, the motor may experience more wear and tear over time, leading to potential damage in the long run.

5. Is it possible to replace a damaged starter capacitor in a starting motor?

Yes, it is possible to replace a damaged starter capacitor in a starting motor. However, it is important to ensure that the replacement capacitor is the correct size and type for the specific motor. It is recommended to consult a professional or refer to the motor's manual for guidance.

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