How to determine whether the AC contactor is working properly?

How to wire the AC contactor in the switchgear?

To wire the AC contactor correctly in the switchgear, it is necessary to distinguish between the main circuit 

and the control circuit. The following is a step-by-step description:

### I. Main Circuit Wiring (Power Supply and Load Connection)

1. **Three-Phase Power Supply Connection**

   - Connect the phase wires (L1, L2, L3) of the three-phase power supply to the input terminals of the main

 contacts of the contactor respectively (usually labeled as **L1, L2, L3** or **1, 3, 5**).

   - Confirm that the power supply voltage is consistent with the rated voltage of the contactor (such as 380V

 or 220V).

2. **Load Connection**

   - Connect the output terminals of the main contacts of the contactor (labeled as **T1, T2, T3** or **2, 4, 6**)

 to the load (such as an electric motor, heater, etc.).

   - If controlling the forward and reverse rotation of the motor, it is necessary to achieve this by changing the

 sequence of the phase wires at the lower port of the contactor.

3. **Ground Wire Connection**

   - Reliably connect the grounding terminal (usually **PE**) of the contactor's housing to the grounding busbar

 to ensure safety.

YouTube：https://youtube.com/shorts/7dHN39hJUBw

### II. Control Circuit Wiring (Coil and Control Signal)

1. **Coil Power Supply**

   - The two terminals (**A1, A2**) of the coil of the AC contactor need to be connected to the control power 

supply:

     - For a **220V coil**: Connect A1 to the phase wire and A2 to the neutral wire.

     - For a **380V coil**: Connect A1 and A2 to two phase wires respectively.

   - Ensure that the control power supply voltage matches the rated voltage of the coil.

2. **Button Control (Taking the Start-Stop Circuit as an Example)**

   - The **stop button** (normally closed contact) is connected in series in the control circuit, with one end 

connected to the phase wire of the power supply and the other end connected to the start button.

   - The **start button** (normally open contact) is connected in parallel with the auxiliary normally open 

contact (**NO**) of the contactor, and the other end is connected to the coil A2.

   - Connect the coil A1 to the neutral wire of the power supply (220V) or another phase wire (380V).

3. **Self-Locking Function**

   - Connect the auxiliary normally open contact (**NO**) of the contactor itself in parallel with both ends of 

the start button to ensure that the contactor remains attracted after releasing the button.

### III. Application of Auxiliary Contacts

- **Auxiliary Normally Open/Normally Closed Contacts** (labeled as **13-14**, **21-22**, etc.) are used to 

expand the control function:

  - The normally open contacts can be used for signal feedback (such as indicator lights).

  - The normally closed contacts can be used for interlocking (such as preventing two contactors from being

 attracted simultaneously).

### IV. Precautions

1. **Voltage Matching**: Confirm that the coil voltage is consistent with the control power supply to avoid

 burning out the coil.

2. **Contact Capacity**: The current of the main contacts needs to be greater than the load current, and the

 auxiliary contacts are only used for the control circuit with a small current.

3. **Arc Extinguishing Device**: An arc extinguishing cover needs to be installed for a contactor with a large

 capacity to prevent faults caused by arcs.

4. **Wiring Inspection**: Use a multimeter to check the continuity of the circuit before energizing to avoid 

short circuits.

5. **Safe Operation**: Disconnect the power supply during wiring to ensure personal safety.

### V. Handling of Common Problems

- **Contactor Not Attracting**: Check whether the coil is open-circuited, whether the control power supply is 

normal, and whether the buttons or auxiliary contacts have poor contact.

- **Contact Erosion**: Clean the oxidized layer on the surface of the contacts, and replace the contactor if it 

is serious.

- **Loud Noise**: Check whether there is foreign matter in the iron core or whether the short-circuit ring is 

damaged.

It is recommended that professional electricians wire according to the specific circuit design to ensure 

compliance with safety regulations.