A common three-phase asynchronous motor has 6 wiring terminals, divided into star connection and delta connection (the main method is based on the connection indicated on the motor's nameplate):
```
W2 U2 V2
*--*--*
* * *
U1 V1 W1
| | |
A B C
```
This type of connection is a Y-type connection with a voltage of 380V.
```
W2 U2 V2
* * *
| | |
* * * * * *
U1 V1 W1
| | |
A B C
```
This type of connection is a Δ-type connection with a voltage of 220V.
It should be noted that some motors do not provide Δ-type connections, so the connection method cannot be changed arbitrarily. Usually, the connection method is written on the nameplate, and the back of the motor wiring box will also clearly indicate the star and delta connection methods.
You mentioned the delta connection. If you find the rotation direction is incorrect, you can randomly swap the sequence of two terminals in the upper row. For the star connection, short the lower row together, connect the upper row to phases A, B, and C. If the rotation direction is wrong, handle it as described above.
Actually, if you think about the definitions of delta and star connections, it becomes clear and easy to understand.
---
I have a three-phase asynchronous motor with two rows of terminals. The upper row is UVW, and the lower row is WUV. Is the delta connection method where UW connects to phase A, VU connects to phase B, and WV connects to phase C?
Yes, the connection method is correct.
For the star connection, how should it be connected? Connect the upper row UVW to the three-phase power supply A, B, and C, and use a jumper to connect the lower row UVW together.
1. Delta connection: UW connects to phase A, VU connects to phase B, and WV connects to phase C (usually the motor comes with 3 shorting bars to connect the corresponding terminals between the upper and lower rows).
2. Star connection: The upper row UVW connects to ABC, and the lower row WUV is shorted (usually the motor comes with 1 shorting bar to short the tail end, i.e., the lower row).
If the upper row is UVW and the lower row is WUV, this indicates that the motor internally uses a delta connection method, and the upper and lower rows are connected using jumpers, as stated on the motor's nameplate for delta connection. The UW connecting to phase A, VU to phase B, and WV to phase C refers to the three-phase power supply required to start the motor, i.e., the external power source. When the three-phase power supply ABC is connected to UVW, the motor starts.
When the motor uses the star connection method, the terminals in the junction box are labeled as follows: the upper row is U1V1W1, and the lower row corresponds to U2V2W2. U2, V2, and W2 are connected using jumpers. The two rows represent the two ends of the winding. U1 and U2 are the head and tail of the U phase. In the star connection method, the three tails are connected together, and the three heads are connected to the three-phase power supply. In the delta connection method, the head of one phase is connected to the tail of the next phase, forming a closed loop as described.