Capacitor Start Capacitor Run Motor
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Capacitor Start Capacitor Run Motor
Capacitor Start Capacitor Run Motor
The Capacitor Start Capacitor Run Motor has a cage rotor, and its stator has two Windings known as Main and Auxiliary Windings. The two Windings are 90 degrees apart from one another. In this method, there are two Capacitors; the starting Capacitor is the one that is used at startup. The second one, known as an RUN Capacitor, is used to run the motor Continuously.
Therefore, this motor is also referred to as a two value Capacitor motor and is given the name Capacitor Start Capacitor Run Motor. Below is the two valve capacitor motor’s connection diagram:
This motor contains two Capacitors, which are denoted by CS and CR. The two Capacitors are connected in parallel during startup. The starting Capacitor, designated Cs, has a short time rating. It’s nearly electrolytic. For the starting torque to be obtained, a significant amount of current is needed. Consequently, the starting Winding’s Capacitive reactance value should be low. Since, XA = 1/2πfCA, the value of the starting capacitor should be large.
The rated line current is smaller than the starting current at the normal operating condition of the motor. Hence, the value of the capacitive reactance should be large. Since, XR = 1/2πfCR, the value of the run capacitor should be small.
A centrifugal switch Sc disconnects the starting capacitor Cs from the circuit as soon as the motor reaches synchronous speed. The capacitor CR is known as an RUN Capacitor because it is always connected to the circuit. The run capacitor is made of oil-filled paper and has a long life rating.
The figure below shows the Phasor Diagram of the Capacitor Start Capacitor Run Motors.
Fig(a) shows the phasor diagram when at the starting both the capacitor are in the circuit and ϕ > 90⁰. Fig (b) shows the phasor when the starting capacitor is disconnected, and ϕ becomes equal to 90⁰.
The torque-speed characteristic of a two-value capacitor motor is shown below:
This kind of motor runs quietly and smoothly. In comparison to motors that only use the main windings, they are more efficient. They are utilised for heavier loads that necessitate frequent starts and require a higher pull-out torque and efficiency. Air compressors, refrigeration, pumping equipment, and other devices all use the two value capacitor motors.