In a CSR motor with 10 microfarad run capacitor and a 110 microfarad start capacitor, the total capacitance will be

In a CSR motor with 10 microfarad run capacitor and a 110 microfarad start capacitor, the total capacitance will be

• A. 100 microfarads
• B. 60 microfarads
• C. 9.17 microfarads
• D. 120 microfarads

Answer: (D)

When a capacitor-start run (CSR) motor starts, the start capacitor and the run capacitor are connected in parallel to the supply to increase starting torque. In parallel, capacitances simply add: C_total = C_run + C_start. So with a 10 µF run capacitor and a 110 µF start capacitor, the total capacitance during starting is 120 µF. After the motor starts, the start capacitor is disconnected, leaving only the run capacitor in circuit (10 µF). If the capacitors were accidentally considered in series, you’d get about 9.17 µF, but that’s not how they’re used during starting.

When a capacitor-start run (CSR) motor starts, the start capacitor and the run capacitor are connected in parallel to the supply to increase starting torque. In parallel, capacitances simply add: C_total = C_run + C_start. So with a 10 µF run capacitor and a 110 µF start capacitor, the total capacitance during starting is 120 µF. After the motor starts, the start capacitor is disconnected, leaving only the run capacitor in circuit (10 µF). If the capacitors were accidentally considered in series, you’d get about 9.17 µF, but that’s not how they’re used during starting.