A single-phase motor generally refers to a low-power single-phase asynchronous motor that is powered by a single-phase AC power source. Because the 220V power supply is very convenient, and the household electricity consumption is also 220V, so the single-phase motor is not only used in production, but also with the daily life of people, the amount of single-phase motor used in household appliances, more and more.
Such as life, there are electric fans, hair dryers, exhaust fans, washing machines, refrigerators, etc.; in the production applications are micro pumps, refiners, threshers, shredders, woodworking machinery, medical equipment.
Today we mainly talk about how to control the forward and reverse of a single-phase motor with buttons and contactors.
If you want to control the forward and reverse of a single-phase motor with buttons and contactors, we need to understand the forward and reverse wiring methods and differences of single-phase motors.
We should first judge the main winding and the secondary winding, and then find the common end, and the common common terminal is connected to the neutral line. The capacitor between the main winding and the secondary winding has two kinds of outgoing lines, namely, the live line 1 and the live line 2. If the live line 1 and the common terminal are energized, the forward rotation is performed, and the live line 2 and the common terminal are reversed.
From the above we can know how to control the single-phase motor forward and reverse with buttons and contactors. Let us assume that the above fire line 1 is A, the fire line 2 is B, and the common end is C.
We first draw a switch to control the forward and reverse circuit diagram, according to this figure we draw the single-phase motor button and contactor control circuit diagram.
ABC represents the three wires of the motor, where the AC wire indicates forward rotation, that is, the contactor KMA controls; the BC wire indicates reverse rotation, which is the contactor KBM control. When the power switch QS is closed, the contactors KMA and KMB are not energized, and the single-phase motor does not operate.
When the start button SB1 is pressed, the contactor coil KMA is energized, the KMA main contact is closed, the AC contact energizes the motor to rotate forward, and the contactor KMA assists the normally open contact closure to realize self-locking, and the released SB1 motor is still energized and forwarded. The normally closed contact is disconnected to achieve interlocking. Even if the SB2 button is pressed, the motor reversing circuit will not be energized, which ensures the safety of the circuit. When the stop button SB is pressed, the KMA is de-energized and the motor stops running.
When the start button SB2 is pressed, the contactor coil KMB is energized, the KMB main contact is closed, the BC contact energized motor is reversed, and the contactor KMB assists the normally open contact closure to achieve self-locking, and the release SB2 motor is still energized and reversed. The normally closed contact is disconnected to achieve interlocking. Even if the SB1 button is pressed, the motor reversing circuit will not be energized, which ensures the safety of the circuit. When the stop button SB is pressed, KMB is de-energized and the motor stops running.