CN2657281Y

CN2657281Y - Single-phase bridge parallel inverter for medium frequency power supply

Info

Publication number: CN2657281Y
Application number: CN 200320110014
Authority: CN
Inventors: 朱兴发
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-10-08
Filing date: 2003-10-08
Publication date: 2004-11-17
Anticipated expiration: 2013-10-08

Abstract

The utility model relates to a 12MC, namely, a single-phase bridge parallel inverter in intermediate frequency power supply, belonging to a technological field of intermediate frequency power supply. The structure is that two left thyristors are connected in series and then connect in parallel to two right thyristors which are also connected in series, and the middle of the concatenation points of the two left thyristors and the concatenation points of the two right thyristors is connected in parallel with a capacitance and an inductance. The utility model is characterized in that shortages in the prior art have been overcome effectively, working performance is stable, and the thyristor is not easy to be damaged when in use, thus the service life of the thyristor has been prolonged greatly.

Description

Single-phase bridge shunt chopper in the intermediate frequency power supply

Technical field

The utility model relates to the single-phase bridge shunt chopper in a kind of 12MC-intermediate frequency power supply, belong to the intermediate frequency power supply technical field.

Background technology

What existing intermediate frequency power supply adopted is non-zero voltage digital scan formula automatic start circuit, so it can't guarantee that equipment is in zero load, underloading, heavy duty or freeze under the stove situation and reliably start.And starting voltage can not all can be started to arbitrary voltage from no-voltage, and electrical network is had impact, starts successfully automatically power per liter to set point.Therefore, complete machine power output function complexity.The frequency conversion circuit of inverter is subjected to load circuit control because of its commutation course, so also need to be provided with other forced commutation device.What the inverter in the existing intermediate frequency power supply adopted is the parallel-connection structure circuit form, and its major defect is the poor stability of service behaviour, and thyristor is also impaired easily.

Summary of the invention

The purpose of this utility model is the defective at above-mentioned existence, proposes a kind of single-phase bridge shunt chopper that need not to be provided with other forced commutation device, is used for intermediate frequency power supply.Technical solution of the present utility model: its structure be the second from left thyristor serial connection back with right two thyristors serial connection back mutually and connect, two thyristors of the serial connection point of the second from left thyristor and the right side be connected in series a little between and connect an electric capacity, inductance.Advantage of the present utility model: it can effectively overcome the defective that prior art has, stable work in work, during work thyristor be difficult for impaired, so prolonged the useful life of thyristor widely.

Description of drawings

Accompanying drawing 1 is an example structure schematic diagram of the present utility model.

Accompanying drawing 2 is process charts of the present utility model

Accompanying drawing 3 is the current-voltage waveform schematic diagrames that flow through in the inverter load.

Accompanying drawing 4 is schematic diagrames of inverter each point waveform.

SCR among the figure ₁-SCR ₄Be thyristor (model KV2500A/2700V), Ld is a direct current reactor, and L is induction furnace (model ZG-3), and C is building-out capacitor (1KVA), and LC forms antiresonant circuit on.A ' A " be respectively thyristor SCR ₁, SCR ₄And thyristor SCR ₃, SCR ₂Between the serial connection point.

Embodiment

Contrast accompanying drawing 1, thyristor SCR ₁-SCR ₄Formed a bridge circuit.Ld is a direct current reactor, and L is an induction furnace, and C is a building-out capacitor, and LC forms antiresonant circuit on.

Contrast accompanying drawing 2, Fig. 2 represents the situation of a duty cycle, SCR before this ₁, SCR ₂Conducting SCR ₃, SCR ₄End, then direct current Id is through reactor Ld, thyristor SCR ₁, SCR ₂Current direction L.C resonant tank, because the inductance value of reactor Ld is bigger, direct current Id is subjected to the restriction of reactor Ld to keep invariable basically, the L.C resonant circuit is subjected to the excitation of a constant current, and produces resonance, and oscillating voltage is sinusoidal wave, the voltage that is to say the capacitor two ends is for sinusoidal wave, as Fig. 2 (a). constantly the polarity of voltage left end at capacitor two ends is for just at this in supposition, and right-hand member is for negative, and capacitor voltage at both ends will be by sinusoidal wave rule variation.The a certain moment before the zero passage (t1 among Fig. 3 constantly) is not triggered thyristor SCR as yet if we are in capacitor voltage at both ends ₃, SCR ₄, form thyristor SCR this moment ₁-SCR ₄The state of conducting simultaneously is as Fig. 2 (b), because thyristor SCR ₃, SCR ₄Conducting, the voltage at capacitor two ends is by thyristor SCR ₃, SCR ₄Be added to thyristor SCR ₁, SCR ₂On, make thyristor SCR ₁, SCR ₂Anode voltage is for negative, and cathode voltage is being for just, thyristor SCR ₁, SCR ₂Turn-off rapidly owing to bear a reverse voltage, that is to say thyristor SCR ₁, SCR ₂Electric current has been given thyristor SCR ₃, SCR ₄After the change of current, direct current is through reactor Ld, thyristor SCR ₃, SCR ₄Encouraged the harmonic wave loop the other way around.Capacitor voltage at both ends continues to change by sinusoidal rule, and the polarity of capacitor voltage at both ends has become left end and is just (as Fig. 2 (C)) for negative right-hand member, and corresponding oscillogram is the t2-t3 moment among Fig. 3.Electric current in load has also changed direction.When the positive voltage of capacitor right-hand member want again zero passage a certain moment (this be equivalent among Fig. 3 t3 constantly), again with thyristor SCR ₁, SCR ₂Touch logically, then form thyristor SCR once more ₁-SCR ₄Conducting simultaneously, but be to make thyristor SCR at this moment ₃, SCR ₄Bear a counter voltage, and electric current has been given thyristor SCR ₁, SCR ₂, this has just finished a duty cycle.From above-mentioned commutation course we as can be seen, as thyristor SCR ₁, SCR ₂Electric current flows into load, thyristor SCR from a direction during conducting ₁, SCR ₂With SCR ₃, SCR ₄The number of times of alternation has also just determined the frequency of output AC electricity.

This frequency conversion circuit is subjected to load circuit control because of its commutation course, so do not need to be provided with other forced commutation device.This is the dissimilarity of it and other frequency conversion circuit, owing to need not add the forced commutation device, therefore the frequency of this frequency conversion circuit and efficient are adapted at using in powerful induction heating and the melting all than higher.

Claims

1, the single-phase bridge shunt chopper in the intermediate frequency power supply is characterized in that the second from left thyristor (SCR ₁), (SCR ₄) serial connection back and right two thyristor (SCR ₃), (SCR ₂) be connected in series the back phase and meet the second from left thyristor (SCR ₁), (SCR ₄) serial connection point A ' and right two thyristor (SCR ₁), (SCR ₄) serial connection point A " between and connect electric capacity (C), induction furnace (L).