Induction motors require capacitors with large capacitances to "jump-start" them.
Single-phase motors can usually be run from a single power source. However, these induction motors cannot self-start when they are required to drive heavy loads. To get them started, an extra "push" must be added. One way to do this is to use starting capacitors placed in the circuit to provide the extra power required to "jump start" the motor to get it rotating. Usually, the capacitor is disconnected once the motor starts running to save on power. However, when the motor speed drops below the recommended level, the capacitor switches back on to give another extra boost, thus maintaining normal operating speeds.
Instructions
1. Select a capacitor with the correct capacitance. This usually is dependent on the motor design. This is necessary to provide the large capacitance values needed to provide the correct matching values to start the motor. The values can be obtained from the motor's manufacturer or by reading on the manufacturer plate attached on the motor.
2. Lay out the circuit by connecting the large capacitor to the auxiliary windings of the motor. One winding must be connected in series and the other winding in parallel to the capacitor.
3. Set up a mechanism that disconnects the starting capacitor once it starts the motor. This is very important, since starting capacitors are not meant to be connected to a high voltage for more than three seconds. If this occurs, it is very likely the capacitor will blow. A centrifugal is commonly used to disconnect this capacitor.
4. Connect a smaller value capacitor to the circuit in parallel and in series to the motor windings in a similar way to the large capacitor. The smaller value capacitor helps to maintain running characteristics while drawing less current.
Tags: large capacitor, smaller value, smaller value capacitor, start motor, starting capacitors, value capacitor