A motor
starter for use with a motor (20) having a main winding (M) and a start winding (S). The
starter has a PTC
thermistor (30) connected in series with the start winding (S). A
triac (40) is connected between PTC
thermistor (30) and a power source line. A
control circuit (50) is connected to the power source line for providing a
voltage for a gate terminal (G) of
triac (40) and an overload
relay (60) is connected between the power source (10) and the motor (20). The
control circuit (50) preferably includes a current detecting circuit (52) for detecting the
inrush current and a
voltage generating circuit (54) for generating the
voltage in response to the detected
inrush current. At the startup of motor (20) the
control circuit (50) allows
triac (40) to turn on by providing the gate terminal (G) with the voltage based on the
inrush current. According to this invention, the
power consumption of the start winding S after the startup of the motor (20) can be almost zero thus providing low
power consumption. In another embodiment not employing a PTC
thermistor, a current detecting circuit and a voltage generating circuit are used to control the on and off states of a first triac (90) which in turn controls the on and off states of a second triac (92) connected in series with the start winding.