Motor Start Capacitor

The Torque Capacitor Start Capacitor is a high-performance, short-duration capacitor designed specifically to deliver the required surge of torque for single-phase AC induction motors during startup. It provides the essential phase shift in the motor’s auxiliary winding that enables motors to overcome inertia and begin rotating reliably.

Key Functions & Working Principle

• In a single-phase induction motor, there are two windings: the main (or run) winding and the auxiliary (or start) winding. These windings normally receive currents in phase if powered directly, which cannot generate a rotating magnetic field — only a pulsating one. EEPower+2Wikipedia+2

• The Torque Start Capacitor is placed in series with the auxiliary winding at startup. It shifts the phase of the current in that winding (lags or leads), creating a difference in phase relative to the main winding. This produces a rotating magnetic field which provides a high starting torque. EEPower+1

• Once the motor reaches a set threshold speed (often ~ 70-80% of full speed), a centrifugal switch or other switching mechanism disconnects the start winding/capacitor so that the motor runs on its main winding (or utilizes a run capacitor for continuous operation). This prevents overheating and ensures efficient operation. EEPower+1

Advantages

• Provides high starting torque, enabling motors to start under load. EEPower+1

• Helps reduce stress on mechanical parts (e.g. belts, gears) by accelerating motor quickly.

• Improves reliability: fewer stalls, fewer overheating events, less damage from sluggish starts.

• Cost effective: replacing a failed capacitor is much cheaper than replacing the motor. Alabama Cooperative Extension System

Limitations & Safety

• Because start capacitors are only for intermittent use, they can overheat or fail prematurely if left in circuit continuously.

• Wrong capacitance or voltage rating (too low or too high) can degrade performance, cause motor to overheat, or even damage capacitor.

• The switching mechanism (centrifugal switch, relay) is critical — if it fails (stays open or closed) the motor will either not start, or be damaged by the capacitor being permanently in circuit. Wikipedia+1

• Capacitor failure modes include: dielectric breakdown, leakage, bulging, loss of capacitance. Regular inspection & proper sizing is important.

Applications

Torque Start Capacitors are ideal for:

• Air conditioning compressors, pumps, blowers, fans

• Refrigeration motors

• Industrial equipment with high inertia loads

• Any single-phase AC motor that must reliably start under load

Why Choose Torque Capacitor

Here are the features that make Torque Capacitor stand out:

• Robust construction with high-grade dielectric materials to handle surge currents at startup.

• Precise capacitance tolerances to ensure correct phase shift and dependable starting torque.

• High voltage ratings to endure spikes, with quality insulation and safety margin.

• Thermal stability for hot environments and vibration-resistant design for long life.

• Full safety compliance and thorough testing (e.g. electrical, mechanical, durability) before release.