【Daily Topic】【Electrical Edition 20170608】
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This post was last edited by yuchenchf on 2017-6-9 08:02. Reward for participation: 2 Wealth. Correct reward: 6 wealth. True or False question: An AC contactor with a rated voltage of 220V can be used with both 220V AC and 220V DC power supplies. ( ) An AC contactor with a rated coil voltage of 220V AC cannot be used with a DC power supply of 220V. This is because the electromagnetic attraction coil of such a contactor is designed to handle the alternating voltage based on its resistance r and inductive reactance XL, with the inductive reactance XL playing a key role. If the coil of an AC contactor is connected to a DC power supply of the same voltage, its inductive reactance becomes zero; as a result, only the coil’s resistance r bears the applied voltage, which leads to a high current flowing through the coil and ultimately causing it to burn out.
An AC contactor with a coil rated voltage of 220V can be used with both 220V AC and 220V DC power supplies. ( × )
An AC contactor with a coil rated voltage of 220V can be used with both 220V AC and 220V DC power supplies. ( Wrong )
Wrong – it definitely can’t be used. The contactor coil will experience overcurrent, leading to severe heating and rapid destruction of the coil.