An air conditioner includes an outdoor unit, a relay circuit which includes a contact and a relay coil, and a control unit which causes a first voltage equal to or higher than an operating voltage or a second voltage lower than the operating voltage and equal to or higher than a retention voltage to be applied to the relay coil. One end portion of the contact is connected to an alternating-current power supply and the other end portion of the contact is connected to the outdoor unit. One end portion of the relay coil is connected to a power supply for driving the relay circuit. The control unit causes a second voltage to be applied to the relay coil after the contact is turned ON, and causes the first voltage to be applied to the relay coil at a predetermined constant period.

A method and system for monitoring a state of a relay switch. The method applies a voltage signal to a solenoid of the relay switch for actuation of the relay switch, monitors over time current flowing through the solenoid after application of the voltage signal, and calculates a back-emf voltage impressed on the solenoid based on an inflection in the current occurring as a plunger of the relay switch moves. The system includes a voltage source, at least one solenoid solenoid having a plunger, a switch connected to the plunger, and a controller configured to data log the voltage applied to the solenoid and the current flowing through the solenoid upon application of the voltage.

The present invention relates to a contactor, a connector and a contactor component. According to the first aspect of the invention, a contactor relates to a switch mechanism, an iron core, an iron core position sensing circuit and a control circuit. The control circuit can measure the position of the iron core by measuring the variation in inductance by using the property that the coil can produce different inductances when the iron core is in different positions in the coil. According to the second aspect of the invention, a connector and contactor component are provided, wherein a control circuit is arranged on a connector, the control circuit comprises a PWM power-saving circuit. The PWM power-saving circuit is integrated on the connector, so that the average driving current of the contactor is reduced and meanwhile, the size of the contactor is reduced.