1. From the winding structure of the coil, if the winding structure of the two coils is exactly the same, then the two end lines at the symmetrical position in space are homonymous ends, so that the homonymous ends of the two coils can be directly observed.

2. Judging from the DC steady-state process: the magnetic field is strengthened, and the positive electrode of the battery is measured to contact the same name terminal; When the magnetic field weakens, the anode of the measuring battery contacts the other end.

3. Measure whether the terminal has the same name without additional circuit (using LCR bridge): take one end in the primary winding, one end in the secondary winding and short-circuit both ends. Test the inductance at the other end of the two groups with a bridge. If the inductance value is greater than the sum of separately measured windings (these two ends have different names), otherwise it is the end with the same name. Synonym: l = l1+L2+2m; Homophone ending: L=L 1+L2-2M.

4. Simple judgment method: connect two windings of the transformer in parallel, and then connect them in series with a light bulb on the AC power supply. The frequency of this AC power supply should be adapted to the transformer core. The core transformer uses the working frequency and the switching transformer uses the switching power supply. Replace both ends of any winding, and then connect the bulb. Comparing the two kinds of wiring, it will be found that the wiring with different brightness and darker brightness indicates that the terminals of the transformer are terminals with the same name.

5. Test method: Measure A 1, A2, B 1, B2, C 1 and C2 of three-phase winding with multimeter resistance. Then connect the ends of three different windings (such as A 1, B 1 and C 1), and then connect the ends of three other different windings (such as A2, B2 and C2).

Use the milliampere range (DC) of the multimeter to lap the (A 1, B 1, C 1) connected head and the (A2, B2, C2) connected head. At the same time, turn the motor rotor by hand to see if the milliammeter pointer swings.

If there is a big swing, switch A 1 with A2 first and try again. If it is still a big swing, first switch A 1 and A2, then switch B 1 and B2 (or C 1 and C2) and try again; If there is still a big swing, replace the original threaded end first, and then replace the unchanged double threaded end until the rotor rotates, and the milliammeter has only a small swing, that is, the connected head is three terminals with the same name (the other three terminals are also the same name).