Motor Starters and Control

Front

What is a Direct Online Starter (DOL)?

Back

A DOL switches a motor on or off with no varying speed or reduction in starting current. It is suitable for small, low-powered motors and can be used for single- or three-phase applications.

Front

What components does a Direct Online Starter (DOL) contain?

Back

A DOL contains an electromagnetic coil that operates a contactor and incorporates overload contacts to trip the device in case of overcurrent. It also provides undervoltage protection to prevent automatic restart during loss of supply.

Front

What is a Star-Delta Starter used for?

Back

A Star-Delta Starter is connected to three-phase motors with six connection points. It starts the motor in star connection to reduce starting current and then switches to delta connection for full load current.

Front

How do Star-Delta Starters prevent short circuits?

Back

Star and delta contactors in Star-Delta Starters are physically interlocked to prevent short circuits.

Front

What is the function of Rotor Resistance Starters?

Back

Rotor Resistance Starters work by introducing variable resistance to the rotor windings, requiring a wound rotor induction motor. This reduces start-up currents in the rotor.

Front

What is an Electronic Motor Starter?

Back

Electronic Motor Starters are used with AC motors to reduce load and torque during start-up by reducing the voltage and gradually ramping it up, thus reducing mechanical stresses on components.

Front

What are Variable Frequency Drives (VFD) used for?

Back

VFDs control motor speed and torque of AC induction motors by adjusting frequency and voltage to match appropriate outputs, saving energy and money. They are commonly used with pumps and fans.

Front

What is reverse-current braking in motor control?

Back

Reverse-current braking is used to prevent continued reversal after the driven parts come to a standstill. Means should be provided to prevent reverse operation.

Front

Why should overload devices in motor control systems be checked?

Back

Overload devices should be checked for correct settings to ensure proper operation and protection of the motor control systems.