In modern industry, three-phase AC motors are widely used in a variety of mechanical equipment. However, during operation, we inevitably encounter situations where motors get damaged. To quickly and accurately determine the cause of motor damage, it’s essential to perform a test on the motor’s lead ends. Below, we’ll provide a detailed introduction to the methods for testing the lead ends of three-phase AC motors, guiding you from beginner to expert level.

I. What are the start and end terminals of a three-phase AC motor?

First, we need to understand what the “start and end terminals” of a three-phase AC motor are. The start and end terminals of a motor refer to the cable connection terminals, which typically connect via winding interfaces to the motor’s rotor and stator. In a three-phase AC motor, there are a total of three cable connection terminals, each corresponding to one of the three phases of the power supply. Properly connecting the motor’s start and end terminals is crucial for ensuring the motor operates correctly; therefore, special attention must be paid when performing tests on these terminals.

II. Tools for Identifying the Motor’s Winding Terminals

Before performing the end-to-end inspection of the motor, we need to prepare several tools. These primarily include a multimeter, cable crimpers, cable terminals, and insulating tape. Among these, the multimeter is an essential tool that can be used to check the connectivity of the cables as well as information such as voltage. Cable crimpers and cable terminals are used to connect the cables, while insulating tape can be used to protect the insulation layer at the cable connection points.

III. Motor End-of-Stroke Detection Method

1. Use a multimeter to test the motor’s lead ends.

First, we need to use a multimeter to check whether the motor’s lead ends are connected correctly. Set the multimeter’s voltage range to AC 200V, then touch the test leads to each of the motor’s three cable connection terminals one by one, and record the voltage reading for each terminal. If the voltage readings at all three terminals are identical, it means the motor’s lead ends are connected correctly. If the voltage readings differ, you’ll need to reconnect the motor’s lead ends.

2. Use cable pliers and cable terminals to connect the motor’s input and output ends.

If you find that the motor’s input and output terminals are connected incorrectly, we’ll need to reconnect the cables. First, use cable pliers to strip a section of insulation from the cable, exposing the wires. Next, connect each wire individually to the cable terminals, then insert the cable terminals into the motor’s cable connection terminals. Finally, wrap the cable connections with insulating tape to ensure that the insulation remains intact and undamaged.

IV. Precautions

1. When performing end-of-motor testing, be sure to disconnect the power supply first to ensure safety.

2. When connecting the cables, make sure to follow the requirements specified in the motor connection diagram to avoid connection errors.

3. When connecting the cable, ensure that the wires and cable terminals are in good contact to avoid poor connections that could lead to motor failure.

Through the introduction above, I believe everyone has now mastered the method for identifying the start and end terminals of a three-phase AC motor. Proper connection of the motor’s start and end terminals is a prerequisite for ensuring the motor operates correctly. Therefore, we need to periodically check these terminals to guarantee the motor’s smooth operation. At the same time, when performing these checks, it’s important to pay attention to safety, connect according to the motor’s wiring diagram, and ensure the quality of the connections.