How to determine whether the motor is damaged when replacing the cooling fan of the WPA50 reducer

When replacing the cooling fan of the WPA50 gearbox, to determine whether the motor is damaged, the principle of simplicity to complexity and from outside to inside can be followed, and the following three steps can be used for troubleshooting.

1、 Preliminary sensory examination

Before conducting any tool measurement, make a preliminary judgment through the senses.

1. Power off operation: Ensure that the fan motor has been completely disconnected from the power supply, which is the first step in safe operation.

2. Smell: Get close to the motor and smell for any pungent burning or insulation paint smell. If so, it indicates that the motor coil is likely to have been burned out.

3. Appearance inspection: Check if there are obvious signs of blackening, deformation, cracks, or damaged wiring terminals on the motor casing.

4. Manual rotation: Gently rotate the fan shaft by hand. A normal motor shaft should rotate smoothly and have even resistance. If there is obvious jamming, friction, abnormal noise or excessive looseness, it indicates that there may be mechanical failure in the bearings or rotors inside the motor.

2、 Multi meter resistance measurement

If no obvious problems are found during the initial inspection, a multimeter can be used for more accurate judgment.

1. Set the multimeter: Set the multimeter to the resistance range (Ω) and select a suitable range (e.g. 200 Ω or 2k Ω).

2. Measure winding continuity: Find the power input lines of the motor (usually two). Connect the two probes of the multimeter to these two wires and measure the resistance value of the winding.

Normal situation: A stable and non-zero resistance value will be measured. The specific values vary depending on the motor power and model, usually ranging from a few ohms to several tens of ohms.

Open circuit fault: If the multimeter displays infinity (OL or 1), it indicates that there is an open circuit in the internal coil of the motor and the motor is damaged.

Short circuit fault: If the resistance value is close to 0 Ω, it indicates that there is a serious short circuit inside the motor, and the motor has been damaged.

3. Measure insulation resistance (optional): If conditions permit, use a megohmmeter (shaker) to measure the insulation resistance between the winding and the motor metal casing. The normal value should be much greater than 0.5M Ω, the higher the better. If the insulation resistance is too low or zero, it indicates that there is a leakage or grounding fault, and the motor is unsafe.