Three-phase locking and frequency conversion integrated machine with dual grid-connected switches and phase locking method

Abstract

The invention relates to a three-phase locking and frequency conversion integrated machine with dual grid-connected switches and a phase locking method. The integrated machine comprises a main loop and a control loop, wherein the main loop comprises a frequency converter, four vacuum contactors, two voltage Hall sensors and a motor, and the control loop comprises four intermediate relays, a PLC and a control switch. When a system works, the starting process and phase locking of an output voltage on a grid power voltage are completed by the frequency converter, on / off control on the vacuum contactors is completed by the PLC through controlling the action of the intermediate relay, so that the functions of power supplied to a motor from the frequency converter during starting and power supplied to the motor from a power grid after phase locking and switching of the vacuum contactors are completed in a steady state are achieved. A three-phase locking technology is used for performing phase locking on the power grid voltage, a power grid phase and an output voltage phase of the frequency converter are locked by a PI controller, and the consistency of the voltage phases during the switching process of a power supply is ensured.

Description

technical field [0001] The invention relates to a motor driving device, in particular to a three-phase phase-locked frequency conversion integrated machine with double grid-connected switches and a phase-locked method. Background technique [0002] As my country's coal enterprises have increasingly higher requirements for the safety of production equipment, more and more mining motor enterprises consider integrating the inverter and motor into the design, and the integrated machine is becoming more and more popular in the market. [0003] The traditional all-in-one machine only mechanically assembles the frequency converter, PLC, relay, motor and other equipment together, which simplifies the difficulty of using the equipment to a certain extent and improves the safety of the driving system. However, in the actual production process, some motors work at the rated voltage and rated speed for a long time, and do not require too much control by the frequency converter. Efficie...

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Problems solved by technology

However, under rated working conditions, although the frequency and amplitude of the voltage output by the inverter are relatively close to those of the power grid, they cannot be guaranteed to be in the same phase. If switching is performed directly, a large inrush current may be generated, which will cause a huge impact on the motor and the power grid.

[0004] In addition, in order to realize the power switching function of the traditional all-in-one machine, the phase sequence of the power grid when the motor is rotating forward is first tested during installation, and the motor can only complete the switching of the power supply when the motor is rotating forward. This feature makes it It is greatly limited in the use of fault tolerance and freedom

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