Open-phase protection circuit for electricity-saving three-phase asynchronous motor

Abstract

The invention discloses an open-phase protection circuit for an electricity-saving three-phase asynchronous motor, which comprises three capacitors with equal capacities, a rectification circuit and a relay. One ends of the three capacitors with the equal capacities are respectively used for being connected with three phases of power wires of the motor. The other ends of the three capacitors and a power middle wire are respectively connected with an input end of the rectification circuit. An output end of the rectification circuit is connected in series with a coil of the relay. A normally closed contact of the relay is connected in series into an AC contactor control circuit. When an electric motor works in an open phase state, the AC contactor control circuit of the electric motor is switched off to make the electric motor stop working, so that the electric motor cannot be damaged and the service life of the electric motor is prolonged. The three capacitors can also play a role of reactive power compensation on a power grid, thus the power factor of the circuit is improved, the local compensation of reactive power is realized, and electric energy is saved. Due to the effect of two connected buttons, the open-phase protection circuit is also avoided being started by mistake and the safety factor is high.

Description

technical field [0001] The invention relates to the technical field of motor protection, in particular to a power-saving three-phase asynchronous motor phase failure protection circuit. Background technique [0002] At present, production machinery is often driven by motors, and three-phase asynchronous motors are widely used as a driving device. The asynchronous motor absorbs reactive power during operation. The larger the capacity, the more reactive power it absorbs, and the greater the impact on the power grid, which not only wastes energy, but also affects the operation of equipment. In addition, during the starting process of the three-phase asynchronous motor, if the power supply is two-phase, the motor cannot run, and if the running motor suddenly cuts off one-phase power supply, due to mechanical inertia, it can still rotate at a slow speed under certain conditions. , but the other two-phase current increases, if the setting current multiple of the thermal relay is ...

AI Technical Summary

Problems solved by technology

The asynchronous motor absorbs reactive power during operation. The larger the capacity, the more reactive power it absorbs, and the greater the impact on the power grid, which wastes energy and affects the operation of equipment

In addition, during the starting process of the three-phase asynchronous motor, if the power supply is two-phase, the motor cannot run, and if the running motor suddenly cuts off one-phase power supply, due to mechanical inertia, it can still rotate at a slow speed under certain conditions. , but the other two-phase current increases, if the setting current multiple of the thermal relay is too large, the motor will overheat, and a burn-in accident may occur, causing losses to production

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