Which of the machines given in the options has the sketched phasor diagram (a) at the time of starting and (b) at the running condition, where Ia is the current in auxiliary winding and Im is the current in main winding?
Which of the machines given in the options has the sketched phasor diagram? (a) at the time of starting and (b) at the running condition, where Ia is the current in auxiliary winding and Im is the current in main winding?
Right Answer is:
Single -phase, capacitor start and capacitor run induction motor
The given phasor diagram is of a single-phase capacitor start capacitor run motor.
Capacitor start capacitor run motors
- This type of motor is designed to operate with the start winding and it is a series capacitor permanently connected to the supply.
- lt has two capacitors connected in parallel in the start winding circuit for starting purposes.
- A start capacitor stays in the circuit long enough to rapidly bring the motor up to a predetermined speed, which is usually about 75% of the full speed and is then taken out of the circuit, often by a centrifugal switch that releases at that speed.
- In a capacitor start and run the motor the function of the running capacitor in series with the auxiliary winding is to Improve power factor.
- Run capacitors are designed for continuous duty while the motor is powered, which is why electrolytic capacitors are avoided.
- As a result, this motor has a higher starting torque as well as a higher efficiency. These motors are employed in sizes ranging from 375 W to 7.5 kW. The power factor of these motors is up to 80% to 100%.