How can you check a 3 phase capacitor working or not?

To check if a 3-phase capacitor is working, you can use a multimeter to measure its capacitance. First, disconnect the capacitor from the circuit and discharge it safely. Set the multimeter to the capacitance measuring mode and connect the leads to the capacitor terminals; the reading should be within the specified range on the capacitor's label. If the reading is significantly lower or shows an open circuit, the capacitor may be faulty and should be replaced.