Introduction

Today, various methods for Starting methods of motor are available. Changes, such as higher starting currents for new energy-efficient motor designs, mean greater focus on starting methods. This is closely linked to the fact that power quality has become a much more important issue in recent years, which has in turn led to greater emphasis on voltage transients associated with the start-up of large motors. This section will outline the various Starting methods of motor used today and provide brief descriptions of their advantages and drawbacks

Direct-on-line starting

As the name suggests, direct-on-line starting means that the motor is started by connecting it directly to the supply at rated voltage. Direct-online starting, (DOL), is suitable for stable supplies and mechanically stiff and well dimensioned shaft systems – and pumps qualify as examples of such systems.

Star-delta starting

The objective of this starting method, which is used with three-phase induction motors, is to reduce the starting current. In starting position, current supply to the stator windings is connected in star (Y) for starting. In the running position, current supply is reconnected to the windings in delta (∆) once the motor has gained speed.

Auto-transformer starting

As the name clearly states, auto-transformer starting makes use of an auto-transformer coupled in series with the motor during starting.

Soft starting

A soft starter is, as you would expect, a device which ensures a soft start of a motor.

Frequency converter starting

Frequency converters are designed for continuous feeding of motors, but they can also be used for start-up only.