Reduced Voltage Starting Circuits 25030

Primary Resistor Reduced Voltage Starter

A timer or another control device is used to bypass the resistors after the motor accelerates to a certain speed.

Closed Transtion Starting

A method of motor starting where the power circuit is never interrupted during the transition from a reduced voltage condition

Autotransformer

Single Winding Transformer. Has multiple taps on the winding to provide different options.

AutoTransformer Reduced Voltage Starter

Operate similarly to primary resistor starters except they provide reduced voltage through the used of a tapped, 3 phase, autotransformer. Basically a step down transformer with multiple taps.

Taps are provided on the autotransformer to permit the user to start the motor at approximatly 50%, 65%, or 80% of the full line voltage.

Step-Down Transformer

A transformer that decreases the output voltage below the level of input voltage.

Taps

A tap is a connection on the secondary coil that creates the ability to obtain multiple levels of voltage from the secondary coil of a transformer.

The 2 Autotransformer control schemes:

Open and Closed Transistion

Open Transition

The motor is momentarily disconnected from the line when switching from reduced voltage to full line voltage. With closed transition control, the motor is not disconnected from the line when changing from reduced to full line.

Part Winding

A motor starting method used with motors having dual or multiple stator windings, where only a portion of the windings is energized initially to reduce starting current and torque, with the remaining windings connected after the motor has partially accelerated.