Dual-speed/delta connection two-speed motor control line - Solutions - China Power

Single-chip microcontroller STM32L151CCU6

Domestic dual-head probe model 038-BB-5.7L, with a unique design where both ends of the needle are rounded rather than pointed.

PESD1CAN electrostatic protection device in SOT23-3 package, 24V bidirectional type.

The control circuit for a two-speed/delta connection motor is illustrated in Figure 21302.

The wiring diagram for the double-star/delta connection motor control is largely similar to the reversible control circuit discussed earlier. As a result, the wiring diagram is not shown in Figure 21302, and a detailed analysis of the principle is omitted. However, some key points are explained below.

1) The parallel connection of two sets of normally open contacts KM2 and KM3 at both ends of the SB2 button ensures that both contactors operate simultaneously. If one contactor fails to close, the other will also be disconnected due to the lack of self-locking function.

2) Several reversible control circuits described above can be modified slightly to accommodate different configurations such as a two-speed motor with double-star/delta connection or a dual-triangle/star, and even a dual-star/dual-star connection motor, which will be covered later. Enthusiastic readers are encouraged to experiment on their own.

3) After completing the wiring and confirming its correctness, it's important to test each speed separately. If the rotation directions of the two speeds are inconsistent, simply swap any two power lines in either KM1 or KM2. This process is commonly referred to as "phase modulation."

4) In Figure 21302 and the control circuits of other multi-speed motors, only one thermal relay is depicted. However, if the motor has different rated currents at various speeds, one thermal relay can be used to protect against overload for one of the two speeds. The normally closed contacts of the two thermal relays should be connected in series within the respective contactor coil circuits to ensure proper protection.