Ac motor is general rotary need two contactor is three-phase ac asynchronous motor, because of the three-phase ac asynchronous motor, power phase sequence in turn, will be turning, the power phase sequence to turn, is to make the article in which any two phase inversion line azimuth is good, for example AB phase inversion between the azimuth of can turn, complete the arbitrary two phase inversion, you need to use two contactor. This is three-phase asynchronous motor, the left is the primary loop, after two contactor completed phase modulation is turning, for example KM1 off, ABC three-phase power supply is on three terminal, in order to motor motor is of being at this moment. When KM2 and three-phase power supply is in accordance with the BAC this order to the motor three terminal, then finished motor rotation function. On the right is the two contactor control circuit, is a kind of interlock circuit and hold circuit, as well as insurance tube. KM1 and conduction KM2 can't together, or you will have the risk of short circuit, so the use of two contactor for contact, in series to the other side of the coil, so a contactor is charged and, will prevent another contactor charged again. Loop inside have their own is turning two start switch, but suspend button only need one. Single phase motor, is launched after switching between vice winding capacitance and the main orientation to complete forward, this will constitute a SNSN and NSNS two magnetic field forms, after two contactor relays may, of course, also can to complete similar control interlock circuit. Actually with the two main contact contactor, after two contactor's main contact, is to switch capacitor in series in the main winding is still inside each winding, so you can change the magnetic field direction, complete is turning. As for the control circuit, and the three-phase asynchronous motor is the same, the same is self-preservation and interlock circuit. Perhaps stepper motor for dc motor, servo motor and so on, generally has the corresponding control device to control them, on the manipulation of the device to the negative signal may be a similar stop switch to switch. Brushless dc motor has, of course, also can through the contactor switch the armature current probably party has done is turning.
