how to test electric motor start capacitor

how to test electric motor start capacitor

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• Visual Inspection: First, disconnect the power supply and wear protective gear such as gloves and safety glasses. Then, observe the capacitor for any signs of damage, looking for leakage, rust, or corrosion. Check if the capacitor's case is bulged, split, or has a blown - open relief port. If any of these situations are found, the capacitor is likely to be faulty and needs to be replaced.


• Continuity Test2: Use a multimeter and rotate the dial to the continuity gear, which is usually marked with a sound - wave icon. Touch the two leads of the multimeter together to check if it is working properly, and you should hear a beeping sound. Then, place the two leads on the two terminals of the capacitor. If the multimeter beeps, it means that the capacitor is allowing current to flow through the dielectric layer, and the capacitor is damaged and needs to be replaced.


• Shorts Test2: If the capacitor housing is metal, this test is required. Keep the multimeter in the continuity gear, place one lead on one terminal of the capacitor, and the other lead on the metal case. Then, repeat the operation for the other terminal. If the multimeter beeps, it indicates that there is a short - circuit between the capacitor's dielectric material and the case, and the capacitor is faulty.


• Capacitance Measurement2: Rotate the dial of the multimeter to the capacitance symbol ( - | | - ). If your multimeter has multiple slots for leads, make sure the red and black leads are inserted into the correct positions for capacitance measurement, usually the red lead should be inserted into the slot marked with the capacitance symbol. Place the two leads on the two terminals of the capacitor to measure the capacitance value. You can also use a professional capacitance meter for a more accurate measurement. Compare the measured value with the capacitance value marked on the capacitor. Generally, the start capacitor should be within ±20% of the stated capacitance. If the measurement result is at the limit or outside this range, the capacitor may be faulty and needs to be replaced.