Solid – State Current Limiting Star – Delta Starter for A 3-Phase Squirrel Cage Induction Motor

Abstract

The high starting current of a squirrel cage induction motor is
undesirable. A solid state current limiting star – delta starter have
been proposed and implemented. The circuit consist of a
microcontroller, optocouplers and power TRIAC. The
microcontroller and optocouplers produces the electrical signal
that turn ON the power TRIAC. The power TRIAC are arranged
such that they can automatically connect the winding of an
induction motor in star mode and after a preset time the motor is
switch to delta connection. On testing with a 2kW motor, the
starting current was limited to 8.2A in star from about 20.2A and
when it switches to delta the current increases to 3.2A from a steady
value of 0.4A. The result indicates that the design can be
implemented in higher power rated squirrel cage induction motors