Motor starter device having reduced power consumption
AssigneeTexas Instruments Incorporated
InventorMitsuru Unno
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AssigneeTexas Instruments Incorporated
InventorMitsuru Unno
Estimating the term…
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.
A motor starter device for use with a motor having a main winding and a start winding, comprising a positive coefficient of temperature (PTC) thermistor connected in series with the start winding, a triac connected between the PTC thermistor and a power source line and a triac control circuit connected in series with the start winding and said main winding and connected to the gate terminal of the triac, the triac control circuit supplying voltage to the gate terminal that is in conformity with the incoming circuit current at the time of the startup of the motor and making the triac conductive at the time of the motor startup, said triac control circuit further comprising a current detecting circuit that detects the incoming circuit current and a voltage generating circuit that produces voltage on the basis of the current that has been detected by the current detecting circuit, said current detecting circuit comprising a current transformer that includes a primary winding connected in series with the power source line and a secondary winding, the current transformer produces the electric current that has been converted from the secondary winding side through the selection of the winding number ratio between the primary winding and the secondary winding and the voltage generating circuit includes a resistor that is connected in parallel with the secondary winding and supplies the voltage that is obtained from the resistor to the gate terminal.
A motor starter device for use with a motor having a main winding and a start winding, comprising a control circuit that controls the current that flows to the start winding in response to the incoming current at the time of the motor startup, the control circuit including a voltage generating circuit that produces voltage that is in conformity with the incoming current, a first triac having a first and a second electrode and a gate terminal and a second triac having a first and a second electrode and a gate terminal, the second electrode of the first triac is connected to the second electrode of the second triac, the first electrode of the first triac is connected to the gate terminal of the second triac, with the voltage from the voltage generating circuit being supplied to the gate terminal of the first triac, the second electrode of the second triac is connected to the start winding and the first electrode of the second triac is connected to the power source line.
Dependencies are inferred from the claim text.