CN2055652U

CN2055652U - Power frequency converter

Info

Publication number: CN2055652U
Application number: CN 89211199
Authority: CN
Inventors: 彭延泰; 吴华仁; 吴建时
Original assignee: NANJING CHEMICAL POWER TRAINING SCHOOL
Current assignee: NANJING CHEMICAL POWER TRAINING SCHOOL
Priority date: 1989-03-14
Filing date: 1989-03-14
Publication date: 1990-04-04

Abstract

The utility model discloses a simple and reliable AC frequency conversion speed regulator-SPWM power frequency converter without microcomputer control, which is comprises a main circuit and a control circuit. The main circuit is a voltage source inverter which comprises six switching circuits with auxiliary network; the control circuit is mainly composed of a piece of special purpose chip (HEF4752V ) of LSIC, six oscillators and six NAND gates. Six drive circuits between the main circuit and the control circuit are used as interfaces. The interface adopts photocoupling and is completely isolated on electricity. The utility model has the advantages that the stepless speed regulation of any three-phase 380V AC electric motor can be realized; the effect of saving can reach 40%; the price is cheaper than existing products.

Description

Power frequency converter

The utility model provides is a kind of simple and reliable and need not micro-processor controlled AC frequency conversion speed regulator---SPWM power converter.

Prior art, the ac speed control method that is it adopts the SPWM scheme, so it has slewing range, dynamic response, operating efficiency, required precision, comprise that function such as easy to use all is better than the function of variable voltage control, serial-resistance speed-regulation, tandem control and electromagnetic clutch speed governing, yet it is owing to be to adopt system controlled by computer, so brought and once invested height, safeguarded problems such as complexity, it has been applied be subjected to certain influence.

The purpose of this utility model is the problem at above-mentioned existence, propose a kind of need not micro-processor controlled SPWM power converter, thereby it is simple, reliable, economical that it is had, and function such as is easy to safeguard, apply.

Technical solution of the present utility model: mainly by main circuit, control circuit two most of SPWM power converters of forming, it is characterized in that main circuit forms by rectifier, LC filter circuit and by the voltage source inverter that the switching circuit of six band auxiliary networks constitutes, each band auxiliary network switching circuit all is made up of R, the C circuit of a High-power Semiconductor Triode and band polarity, and fast diode D of the emitting stage of every High-power Semiconductor Triode serial connection plays jamproof effect; Control circuit is made up of oscillator and six NAND gate circuit (74LSoo) that the special chip (HEF4752V) of a slice LSlC and six Schmidt trigger CD40106B form, at the drive circuit QD1-6 that leads, is provided with between the control circuit six double as interfaces, its interface is to adopt the photoelectricity coupling, isolate fully on electric, and each drive circuit all has independently, and DC power supply 1-6 requires and the anti-crosstalk requirement to adapt to the direct-coupled level conversion that High-power Semiconductor Triode is driven.The special chip that uses a slice LSlC in addition several piece gate circuit is formed the pwm signal generator, the core of this signal generator is that a slice is encapsulated in large scale integrated circuit (LSIC) HEF4752V in the double 28 pin shells of standard, is abroad to design, make with the LOCMOS technology for Sine Pulse Width Modulation.It can produce three pairs of corresponding complementary PWM waveforms as required, goes to drive the inverter bridge of being made up of 6 switch elements, to produce the three-phase output of symmetry.Because adopt totally digitilized circuit, the repetition rate of this pwm signal (can artificially select) remains inverter output frequency f _{Ou is big}Strict integral multiple, this has just safeguarded three-phase equilibrium, makes generator loss lower.HEF4752V is in the GTR driving condition in the circuit; Four clock inputs are fixed three, and the oscillator of forming by six Schmidt trigger CD40106B produces corresponding frequencies, is obtained by six NAND gate circuit 74LSoo shaping again.Wherein voltage control clock VCT is decided to be f _{Vc is big}=6720 * f _e(motor nominal operation frequency); Reference clock RCT is by the maximum switching frequency f of inverter _S(max)Decision is decided f under requiring aspect sine wave output shape and the switching loss two taking all factors into consideration _S(max), this circuit is got f _S(max)=1000Hz; For easy, economical, get output postponement clock OCT and equal RCT, putting switching value input K=" 1 " (positive logic) simultaneously is in order to reduce the requirement to main switch element, also to have improved coefficient of safety simultaneously to obtain bigger complementary interval, so to do.The unique external conditioning signal Ugd of this signal generator converts the pulse of 0～150KHz adjustable clock to through the homemade simple and easy voltage controlled oscillator chip 5GVFC32 of a slice, and input HEF4752V is as frequency control clock FCT after NAND gate 74LSoo shaping.Like this, when Ugd when 0～15V changes, HEF4752V can export corresponding six road PWM ripples, is coupled to main circuit through photoelectrical coupler, finally exports output frequency f on the major loop inverter bridge _{Ou is big}=0～f _e, output voltage, U _{Ou is big}/ f _{Ou is big}The three-phase sine-wave of=constant is shown in its operating characteristic (accompanying drawing 2).Main circuit adopts GTR to make switch element.Here each GTR all has a RC auxiliary network parallel connection, band polarity to absorb network as the turn-off power loss of GTR on the inverter bridge; And (in the side circuit because of voltage withstand class cause with two a strings) fly-wheel diode is to provide one to keep the equidirectional mobile path of load current; All go here and there a diode D under each GTR, this is to prevent six road keys of crosstalking between driving, and can strengthen the anti-back-pressure ability of GTR.The major loop inverter bridge is except the protection that above-mentioned auxiliary network provides, and the isolation between each drive circuit is a key! Here six drive circuits adopt six D.C. regulated power supplies independent of each other (1-6) to be working power respectively.This not only considers from the level angle, the more important thing is to prevent that crosstalking of each road signal is provided with.Experimental results show that: do not take this measure system just can't work.

The diode of auxiliary network must be a fast diode in the major loop inverter bridge; Especially continued flow tube, tR must have strict restriction to its reverse recovery time, otherwise can damage with its complementary GTR.

Being provided with conventional accelerating circuit in the drive circuit is made up of C1, R6 and D2.

Accompanying drawing 1 is circuit theory diagrams of the present utility model.

Accompanying drawing 2 is operating characteristic schematic diagrames of the utility model system.

When exporting less than rated value, U _{Ou is big}/ f _{Ou is big}=constant is output as sine wave, f _eWhen design, determine general power taking machine rated value, i.e. f _e=50Hz, Ue=380V increases control voltage signal U _GdnMake f _{Ou is big}＞f _eWhen (rated frequency), U _{Ou is big}No longer increase, this moment, sine wave output began to become " fat ", and high order harmonic component increases, and continues to increase f _{Ou is big}Make output waveform become square wave.

Through practical application, output characteristic reaches the index that rich seven companies of Japan adopt the FVR-G2 Series Frequency Converter of 16 digit microcomputer control.Did a such main circuit fatigue test, when certain in main circuit was burnt fully to complementary switch circuit, this control circuit was still excellent.It is low, simple and reliable, easy to use that the SPWM power converter has a cost, is easy to advantages such as maintenance.

T1-6 in the accompanying drawing is High-power Semiconductor Triode GTR, and D is fast diode, and R is resistance, and C is electric capacity, and QD1-4 is drive circuit, and CD40106B and 74LSoo are that gate circuit, Go111 are photoelectrical couplers, and 1-6 is dc source.

Claims

1, a kind of mainly by main circuit, control circuit two most of SpWM power converters of forming, it is characterized in that main circuit forms by rectifier, LC filter circuit and by the voltage source inverter that the switching circuit of six band auxiliary networks constitutes, each band auxiliary network switching circuit all is made up of R, the C circuit of a High-power Semiconductor Triode and band polarity, and fast diode D of the emitting stage of every High-power Semiconductor Triode serial connection plays jamproof effect; Control circuit is made up of oscillator and six NAND gate circuit (74LSoo) that the special chip (HEF4752V) of a slice LSIC and six Schmidt trigger CD40106B form, at the drive circuit QD1-6 that leads, is provided with between the control circuit six double as interfaces, its interface is to adopt the photoelectricity coupling, isolate fully on electric, and each drive circuit all has independently DC power supply 1-6, requires and anti-tampering requirement to adapt to the direct-coupled level conversion that High-power Semiconductor Triode is driven.