- Magnetic starters find their primary usage with multi-phase electric circuits. Multi-phase circuits are designed for 220 V and higher power supplies. The magnetic starter acts similarly to a solenoid in the car's motor. The magnetic starter initiates the motor's rotation. When the motor's rotation attains specified velocity, the magnetic starter disengages and the full current levels are connected to the electric motor.
- 120 V table saw electrical motors are designed to initiate under low-load conditions and spin at high rotational rates. At high speeds, the rotational inertia of the blade overcomes the physical strength of the wood and cuts the wood cleanly. While the motor starts, the circuitry is designed to consume electrical energy in order to create the high rotation rates. Imagine riding a bicycle uphill. If the rider ascends the hill with a running start, he uses much less energy than if starting from a dead stop at the bottom of the hill. Riding up the hill from a dead stop accurately describes a high load start. The table saw motor is not designed to withstand this level of resistance.
- If an electric motor initiates under a high load condition, the electrical resistance inside the electric motor causes increased temperatures in the motor, which then feed back into the entire circuit. Imagine turning on a water hose and holding the palm of a hand over the hose's outlet. The water pressure within the hose either pushes the hand away or builds up pressure within the line. The same principle applies in an electric circuit. When initiating the electric current, the electricity is consumed by the electric motor's rotation. In this case, the electrical energy leaves the line. If not consumed, the current backs up into the electric wires, converting electrical energy into heat energy, risking a thermal overload.
- Magnetic starters are also used to control the rotation of electric motors that reverse direction during use. The magnetic starter controls the slowdown, stop and restart stage of a motor initiating a rotational reversal. The magnetic starter prevents high load resistance and stress from damaging the motor's internal components. Since the table saw motor is designed to turn in one direction, the magnetic starter is not used for 120 V table saw motors.
- Magnetic starters are designed and used in some 120 V electric motors. When the 120 V motor initiates under high load conditions, such as when attached to a gearbox or driving a pump, the magnetic starter prevents thermal overload within the 120 V electric motor. Regarding a standard 120 V table saw, these conditions rarely apply. Therefore the magnetic starter is not necessary.
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