Three-phase power input phase lack detection circuit

Abstract

The invention relates to an input lack-phase detection circuit of a three-phase power supply, comprising a first current-limiting resistor, a second current-limiting resistor and a third current-limiting resistor which are respectively connected to a first phase line, a second phase line and a third phase line, the input lack-phase detection circuit also comprises a pull-up resistor, a third diode with a cathode which is connected to the third current-limiting resistor, a first optocoupler and a second optocoupler with output ends which are connected in series between the pull-up resistor and signal ground, a first diode which is connected with an input end of the first optocoupler in series between the first current-limiting resistor and an anode of the third diode, a second diode which is connected with the input end of the second optocoupler in series between the second current-limiting resistor and the anode of the third diode, a first capacitor which is connected with the input end of the first optocoupler in parallel and a second capacitor which is connected with the input end of the second optocoupler in parallel, and the pull-up resistor is connected to the output end of the lack-phase detection circuit. The input lack-phase detection circuit reduces the loss on the current-limiting resistors, so the current-limiting resistors are difficult to damage due to small heat, the reliability of the circuit is improved and the service life is prolonged.

Description

technical field [0001] The invention relates to the field of frequency converters, in particular to a three-phase power supply input phase loss detection circuit. Background technique [0002] Frequency conversion speed regulation has become the mainstream speed regulation method, and the frequency converter is the core part of its speed regulation system. To ensure the reliable and safe operation of the frequency converter, it is necessary to provide various protections for the frequency converter. The input phase loss protection circuit, as the most commonly used and important protection circuit in the inverter, has been widely used in the inverter. [0003] Such as figure 1 Shown is a schematic diagram of a phase loss protection circuit in an existing frequency converter. The resistance part (ie R1-R6) of the three-phase power input terminal is used to limit the current of the three-phase power input, and the three-phase full-wave rectification part (ie D1-D3) is used t...

AI Technical Summary

Problems solved by technology

[0007] The technical problem to be solved by the present invention is to provide a three-phase power input phase loss detection circuit for the defects of high energy consumption, low reliability and low circuit life of the above-mentioned phase loss detection circuit

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