capacitorrun

Capacitor-run refers to a type of single-phase induction motor that uses a permanently connected run capacitor in series with its auxiliary winding to create a phase-shifted current. The main winding is powered directly from the AC supply, while the auxiliary winding carries current through the capacitor, producing a rotating magnetic field and improved torque during operation. In permanent-split capacitor (PSC) designs the run capacitor remains in circuit at all times; in capacitor-start, capacitor-run (CSCR) designs a start capacitor provides a larger phase shift briefly during startup and is then disconnected.

Operation and design: The capacitor shifts the phase of current in the auxiliary winding to produce a more effective starting and running torque. The motor typically runs at a speed slightly below synchronous speed, with slip determined by load. The run capacitor value is chosen to achieve the desired phase angle and torque for the rated load, voltage, and frequency. Some designs include a centrifugal switch to disconnect a separate start winding after startup.

Advantages: Capacitor-run motors generally offer higher starting and running torque, improved running efficiency, and better power factor than simple split-phase motors. They are simpler and quieter than motors requiring full start-only windings and are well-suited for belt-driven machines and variable loads where consistent speed is important.

Limitations and considerations: The performance depends on capacitor quality, temperature, and aging, and run capacitors must be properly rated for voltage and environment. They are usually not as versatile for speed control as three-phase systems and may be more costly than basic split-phase motors for small power levels.

Applications: Often found in household appliances such as ceiling fans and compressors, HVAC equipment, certain pumps, blowers, and other compact machines where reliable, moderate starting torque and smooth running are desirable.