CN2483878Y - Microelectronic motor protector with high performance price ratio - Google Patents

Abstract

The utility model discloses a microelectronic motor protector with high cost performance. Three-phase current transformers of the three-phase current transformers are respectively connected in parallel with resistors to convert current signals into voltage signals. Connected, the V/F converter converts the voltage signal into a digital pulse signal, and the single-chip microcomputer system without A/D judges the count value of the three-phase current signal and the power supply voltage sampling signal to determine whether there is a fault. Compared with the prior art, the utility model is reliable in operation and has the main protection functions of motor overload, phase failure, locked rotor, three-phase unbalance, overvoltage and undervoltage.

Description

A Cost-effective Microelectronic Motor Protector

The utility model belongs to a novel motor protector, which belongs to the generation, transformation or distribution of electric power.

Due to the unstable performance and poor protection function of bimetal thermal relays, the development direction of motor protectors is motor protectors using microelectronic chips. According to the search, there are various products and discussions on electronic or intelligent motor protectors. The paper "A New Type of Digital Motor Comprehensive Protection Device" published by Zhang Lian et al. , Xu Shuyan published a paper "A Design Scheme for Electronic Motor Protection Relay" in "Electrical Switches" magazine 1999.No3, taking the intelligent digital display electric monitoring system JDB-LQ series of Zhejiang Cangnan Shuanghua Electric Co., Ltd., etc. Products are typical products. However, some of these schemes only have overload or phase failure protection functions, and some use single-chip microcomputer chips with complex circuits and high prices. Therefore, these schemes either have low performance indicators or high prices, and cannot be popularized and applied on a large scale.

The purpose of this utility model is to address the above-mentioned deficiencies, and develop a microelectronic type with main protection functions of overload, phase failure, locked rotor, three-phase unbalance, overvoltage and undervoltage, high performance index and low cost. motor protector.

The purpose of this utility model is achieved in that the three-phase current transformers are respectively connected in parallel with the resistors to convert the current signal into a voltage signal, and the voltage signal output by the resistor and the voltage signal output by the power transformer are respectively connected to the multi-channel analog switch through the rectifier circuit The four input ports of the channel, the signal after channel selection is connected to the peak sampling circuit through the output terminal of the multi-channel analog switch, the signal after peak sampling is connected to the amplifier circuit through the output terminal, and the output terminal of the amplifier circuit is connected to the V/F converter The input terminals of the V/F converter are connected, and the V/F converter converts the voltage signal into a digital pulse signal, and the output digital pulse signal is connected to the input port of a low-cost single-chip system without A/D through the output terminal of the V/F converter. Counting, the single-chip microcomputer system without A/D respectively judges the count value of the three-phase current signal and the power supply voltage sampling signal to determine whether there is a fault. If it is a fault, the output port of the single-chip microcomputer system without A/D sends out a tripping signal and The indicator light and the relay are driven by the driving circuit.

Compared with the prior art, the utility model is reliable in operation, has the main protection functions of motor overload, phase failure, locked rotor, three-phase unbalance, overvoltage and undervoltage, can accurately count signal values, and has a simple circuit. And a low-cost motor protector without an A/D microcontroller is adopted.

The utility model will be further described below in conjunction with the accompanying drawings

Fig. 1 is the structural representation of the utility model

Fig. 2 is the schematic block diagram of the circuit of the present utility model

Fig. 3 is the schematic block diagram of the software of the utility model

In the figure, Z1, Z2, and Z3 are three-phase current transformers; R1, R2, and R3 are resistors; Z4 is a power transformer; X1, X2, X3, and X4 are rectifier circuits; D is a single-chip system without A/D; E1 is a multi-channel analog switch; E2 is a peak sampling circuit; E3 is an amplifier circuit; E4 is a V/F converter; E5 is a drive circuit; E6 is an indicator light and a relay.

It can be seen from Figure 1 that the signals output by the three-phase current transformers Z1-Z3 and the power transformer Z4 are sent to the counting pulse generation and control system K, the setting current adjustment potentiometer W is connected to K, and the single-chip system D counts through K and sends out a signal For K, K is connected to the indicator light and relay E6.

It can be seen from Figure 2 that the connection relationship is that the three-phase current transformers Z1-Z3 are respectively connected in parallel with the resistors R1-R3 to convert the current signal into a voltage signal, and the voltage signal output by R1-R3 and the voltage signal output by the power transformer Z4 are respectively passed through The rectifier circuit X1-X4 is connected to the four input ports of the multi-channel analog switch E1, the signal after channel selection is connected to the peak sampling circuit E2 through the output terminal of the multi-channel analog switch E1, and the signal after the peak sampling is connected to the output terminal of E2. Amplifying circuit E3, the output terminal of E3 is connected with the input terminal of V/F converter E4, E4 converts the voltage signal into a digital pulse signal, and the output digital pulse signal is connected to a low-cost non-A/D converter through the output terminal of E4 The input port of the single-chip microcomputer system D counts, and D respectively judges the count value of the three-phase current signal and the power supply voltage sampling signal to determine whether there is a fault. If it is a fault, the output port of D sends a tripping signal and is driven by the drive circuit E5. Lamp and relay E6.

It can be seen from Figure 3 that the single-chip microcomputer system D first initializes, and then judges whether the power supply voltage meets the requirements. If it meets the requirements, it sends a closing signal, and then conducts current and voltage sampling to judge whether there is a phase failure or three-phase imbalance. Three-phase unbalance protection program, otherwise continue to judge overvoltage or undervoltage, if yes, enter the overvoltage and undervoltage protection program, otherwise judge whether it is blocked, if yes, enter the stall protection program, otherwise judge whether it is overloaded, yes then Enter the overload protection program, otherwise, the current and voltage sampling will be carried out again, and this cycle will be carried out.

It can be seen from the above: three-phase current transformer Z1-Z3, resistor R1-R3, power transformer Z4, rectifier circuit X1-X4, single-chip microcomputer system D without A/D, multi-channel analog switch E1, peak sampling circuit E2, amplification Circuit E3, V/F converter E4, drive circuit E5, indicator light and relay E6, the connection relationship is that three-phase current transformers Z1-Z3 are respectively connected in parallel with resistors R1-R3 to convert current signals into voltage signals, and R1- The voltage signal output by R3 and the voltage signal output by the power transformer Z4 are respectively connected to the four input ports of the multi-channel analog switch E1 through the rectification circuit X1-X4, and the signal after channel selection is connected to the peak value through the output terminal of the multi-channel analog switch E1 Sampling circuit E2, the signal after peak sampling is connected to the amplifier circuit E3 through the output terminal of E2, the output terminal of E3 is connected to the input terminal of V/F converter E4, E4 converts the voltage signal into a digital pulse signal, and the output digital pulse The signal is connected to the input port of the low-cost single-chip microcomputer system D without A/D through the output terminal of E4 for counting. D separately judges the count value of the three-phase current signal and the power supply voltage sampling signal to determine whether there is a fault. If it is a fault, The D output port sends a tripping signal and drives the indicator light and relay E6 through the driving circuit E5.

Claims (1)

1. the microelectronics type motor protector of a high performance-price ratio; it is characterized in that: threephase current transformer (Z1; Z2; Z3) respectively with resistance (R1; R2; R3) parallel connection; resistance (R1; R2; R3) voltage signal of Shu Chu voltage signal and power transformer (Z4) output is respectively through rectification circuit (X1; X2; X3; X4) be connected to four input ports of multiway analog switch (E1); signal after channel selecting is connected to peak value sampling circuit (E2) through the output of multiway analog switch (E1); signal behind the peak value sampling is connected to amplifying circuit (E3) through (E2) output, and the input of the output of amplifying circuit (E3) and V/F converter (E4) joins.

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