News Details

Home > News >

Company news about Which Type of Capacitor Is Used in Single Phase Motor? A Complete Technical Guide

Events

Cases

Mrs. Anny Song

motorexport@bimo-idea.com

86--18802094629

Contact Now

Which Type of Capacitor Is Used in Single Phase Motor? A Complete Technical Guide

2026-06-02

Why Do Single Phase Motors Need Capacitors?

Single phase motors require capacitors because a single-phase AC supply produces a pulsating magnetic field that cannot generate the rotating magnetic field needed to self-start — a capacitor creates the necessary phase displacement to produce starting torque.

Three-phase motors generate a naturally rotating magnetic field from three current phases separated by 120°. Single phase motors receive only one phase, producing a field that alternates but does not rotate. Without rotation in the magnetic field, the rotor has no preferred direction of spin and cannot start on its own — a phenomenon known as the single-phase problem.

The solution is to create an artificial second phase using a capacitor connected in series with an auxiliary (start) winding. The capacitor introduces a phase shift of up to 90° between the main winding current and the auxiliary winding current, producing an approximate two-phase condition sufficient to generate a rotating magnetic field and self-starting torque.

A start capacitor is in circuit only during startup (typically 0.5–3 seconds) and then disconnected by a centrifugal switch or current relay
A run capacitor remains in circuit continuously during operation to improve power factor, efficiency, and running torque
Some motors use both a start and a run capacitor — known as capacitor start / capacitor run (CSCR) motors — for maximum performance

Which Type of Capacitor Is Used in Single Phase Motor? A Complete Technical Guide

1. Core Overview of Capacitors for Single-Phase Induction Motors

Single-phase AC induction motors cannot self-start inherently due to uniform single-phase alternating magnetic field; a phase-shift capacitor splits single-phase supply into two out-of-phase currents to generate rotating magnetic field for starting/running. Two distinct capacitor types are standard based on motor design: Start Capacitor and Run Capacitor, plus rare Dual-Value (Start+Run combined) capacitors for special motors.

Capacitance unit: Microfarad (μF); rated voltage ≥1.1~1.25× motor operating supply voltage (230V/110V mains globally).

2. Start Capacitors (Starting Capacitor – Short-Duty Operation)

2.1 Type Specification

Non-Polarized Electrolytic Capacitors (Motor Start Electrolytic)

Construction: Aluminium wet electrolytic, non-polarized specifically engineered for AC intermittent duty; never use DC polarized electrolytic capacitors.
Typical Capacitance Range: 50μF ~ 1500μF, high capacitance value for large starting torque.
Rated Voltage: 250VAC, 330VAC, 450VAC common ratings for 220–240V single-phase grid.

2.2 Working Principle & Duty Cycle

Connected in series with motor auxiliary (start) winding alongside a centrifugal switch mounted on motor rotor shaft.
Only active during motor startup (0.5~3 seconds): Once motor reaches ~75–80% of rated synchronous speed, centrifugal switch opens and disconnects start capacitor entirely from circuit.
Intermittent short-time duty only: Designed for brief peak current surge during startup; continuous energization causes overheating, electrolyte drying, capacitor bulge/burst.

2.3 Application Motors

Split-phase, Capacitor-Start Induction Motor (CSIR): Compressors, water pumps, small air compressors, heavy-duty workshop single-phase motors requiring high starting torque.

3. Run Capacitors (Running Capacitor – Continuous Full-Time Operation)

3.1 Type Specification

Metallized Polypropylene Film Capacitor (CBB60 / CBB65 is industry standard for motor run)

Dielectric: Polypropylene PP film with vacuum-metallized zinc/aluminium electrode; self-healing property for minor internal breakdown.
Capacitance Range: Low value 1μF ~ 100μF, much smaller than start capacitors.
Standard AC Voltage Rating: 250VAC, 350VAC, 400VAC, 450VAC, 500VAC.
Construction: Cylindrical plastic/metal can sealed package, oil-filled or dry-type (CBB65 mostly oil-filled for heat dissipation; CBB60 dry).

3.2 Working Principle & Duty Cycle

Permanently wired in series with auxiliary winding for 24/7 continuous operation across full motor runtime.
Two core functions:
1. Creates permanent phase shift between main & auxiliary winding to maintain rotating magnetic field during normal running speed;
2. Improves motor power factor (PF correction), reduces input reactive power, lowers winding heating, boosts running efficiency.
No centrifugal switch in run-only circuit.

3.3 Application Motors

Capacitor-Start Capacitor-Run (CSCR) / Permanent Split Capacitor Motor (PSC – most common household motor):

Household ceiling fans, washing machine motors, fridge compressors, small water pumps, air conditioner blower motors, garden pumps.

Some compact single-phase motors adopt dual-rated metallized film dual-capacitor unit (two capacitance values inside single casing):

Internal split: One high-C section = temporary start function (cut off via relay instead of centrifugal switch); low-C section stays permanently in circuit as run capacitor.
Mainly used for mini hermetic compressors and compact integrated pump motors to reduce wiring space.

News Details

Home > News >

Company news about-Which Type of Capacitor Is Used in Single Phase Motor? A Complete Technical Guide

Events

News

Cases

Which Type of Capacitor Is Used in Single Phase Motor? A Complete Technical Guide

2026-06-02

Why Do Single Phase Motors Need Capacitors?

A start capacitor is in circuit only during startup (typically 0.5–3 seconds) and then disconnected by a centrifugal switch or current relay
A run capacitor remains in circuit continuously during operation to improve power factor, efficiency, and running torque
Some motors use both a start and a run capacitor — known as capacitor start / capacitor run (CSCR) motors — for maximum performance

Which Type of Capacitor Is Used in Single Phase Motor? A Complete Technical Guide

1. Core Overview of Capacitors for Single-Phase Induction Motors

Capacitance unit: Microfarad (μF); rated voltage ≥1.1~1.25× motor operating supply voltage (230V/110V mains globally).

2. Start Capacitors (Starting Capacitor – Short-Duty Operation)

2.1 Type Specification

Non-Polarized Electrolytic Capacitors (Motor Start Electrolytic)

Construction: Aluminium wet electrolytic, non-polarized specifically engineered for AC intermittent duty; never use DC polarized electrolytic capacitors.
Typical Capacitance Range: 50μF ~ 1500μF, high capacitance value for large starting torque.
Rated Voltage: 250VAC, 330VAC, 450VAC common ratings for 220–240V single-phase grid.

2.2 Working Principle & Duty Cycle

Connected in series with motor auxiliary (start) winding alongside a centrifugal switch mounted on motor rotor shaft.
Only active during motor startup (0.5~3 seconds): Once motor reaches ~75–80% of rated synchronous speed, centrifugal switch opens and disconnects start capacitor entirely from circuit.
Intermittent short-time duty only: Designed for brief peak current surge during startup; continuous energization causes overheating, electrolyte drying, capacitor bulge/burst.

2.3 Application Motors

Split-phase, Capacitor-Start Induction Motor (CSIR): Compressors, water pumps, small air compressors, heavy-duty workshop single-phase motors requiring high starting torque.

3. Run Capacitors (Running Capacitor – Continuous Full-Time Operation)

3.1 Type Specification

Metallized Polypropylene Film Capacitor (CBB60 / CBB65 is industry standard for motor run)

Dielectric: Polypropylene PP film with vacuum-metallized zinc/aluminium electrode; self-healing property for minor internal breakdown.
Capacitance Range: Low value 1μF ~ 100μF, much smaller than start capacitors.
Standard AC Voltage Rating: 250VAC, 350VAC, 400VAC, 450VAC, 500VAC.
Construction: Cylindrical plastic/metal can sealed package, oil-filled or dry-type (CBB65 mostly oil-filled for heat dissipation; CBB60 dry).

3.2 Working Principle & Duty Cycle

Permanently wired in series with auxiliary winding for 24/7 continuous operation across full motor runtime.
Two core functions:
1. Creates permanent phase shift between main & auxiliary winding to maintain rotating magnetic field during normal running speed;
2. Improves motor power factor (PF correction), reduces input reactive power, lowers winding heating, boosts running efficiency.
No centrifugal switch in run-only circuit.

3.3 Application Motors

Capacitor-Start Capacitor-Run (CSCR) / Permanent Split Capacitor Motor (PSC – most common household motor):

Household ceiling fans, washing machine motors, fridge compressors, small water pumps, air conditioner blower motors, garden pumps.

Some compact single-phase motors adopt dual-rated metallized film dual-capacitor unit (two capacitance values inside single casing):

Internal split: One high-C section = temporary start function (cut off via relay instead of centrifugal switch); low-C section stays permanently in circuit as run capacitor.
Mainly used for mini hermetic compressors and compact integrated pump motors to reduce wiring space.

AC Electric Motor

Three Phase Motor

Single Phase Motor

NEMA Standard Motor

Vertical Hollow Shaft Motor

High Voltage Electric Motor

Gost Standard Motor

Explosion Proof Motor

PMDC Motor

AC Electric Motor

Three Phase Motor

Single Phase Motor

NEMA Standard Motor

Vertical Hollow Shaft Motor

High Voltage Electric Motor

Gost Standard Motor

Explosion Proof Motor

PMDC Motor

News Details

Company news about Which Type of Capacitor Is Used in Single Phase Motor? A Complete Technical Guide

News

Cases

Which Type of Capacitor Is Used in Single Phase Motor? A Complete Technical Guide

Why Do Single Phase Motors Need Capacitors?

1. Core Overview of Capacitors for Single-Phase Induction Motors

2. Start Capacitors (Starting Capacitor – Short-Duty Operation)

2.1 Type Specification

2.2 Working Principle & Duty Cycle

2.3 Application Motors

3.1 Type Specification

3.3 Application Motors

Company news about-Which Type of Capacitor Is Used in Single Phase Motor? A Complete Technical Guide

News

Cases

Which Type of Capacitor Is Used in Single Phase Motor? A Complete Technical Guide

Why Do Single Phase Motors Need Capacitors?

1. Core Overview of Capacitors for Single-Phase Induction Motors

2. Start Capacitors (Starting Capacitor – Short-Duty Operation)

2.1 Type Specification

2.2 Working Principle & Duty Cycle

2.3 Application Motors

3.1 Type Specification

3.3 Application Motors