CN2332107Y - Medium-frequency induction heating semi-control bridge current-mode inverter - Google Patents

Abstract

The utility model relates to a current-mode inverter used for an intermediate frequency induction heating power supply, which comprises an inductor, a compensation capacitor and bridge arms, wherein each bridge arm is composed of a thyristor. The utility model is characterized in that only the two bridge arms are utilized to be connected with one end of the inductor respectively; the direct current of the power supply is switched on and switched off in the two bridge arms by turns; the direct current is switched on from a tap of an inductor coil, the direct current can extract the tap from the center of the inductor coil, or can extract tap from the right and the left sides which are symmetrical to the center of the coil; after that the taps are respectively connected with a diode to lead out the two half waves of the direct current, or two or a plurality of half control bridge inverters which are connected in the circuit in series are adopted. Thereby, the output of the intermediate frequency voltage is obviously improved so as to make the utility model suitable to the power supply requirements of induction heating devices with small or large sizes.

Description

Frequency Induction Heating half control bridge current source inverter

The utility model belongs to the Frequency Induction Heating circuit arrangement, relates to current source inverter.

The current source inverter schematic circuit that existing Frequency Induction Heating is used as shown in Figure 1.Four brachium pontis 1～4 that it comprises inductor Lr and is connected the building-out capacitor C between the inductor two ends and is made up of controllable silicon.The power supply direct current takes turns break-make at brachium pontis 1 and 3 and 2 and 4 two pairs of brachium pontis, and inductor Lr and capacitor C constitute oscillation circuit direct current is transformed into electric current of intermediate frequency.The relation of its voltage of intermediate frequency and direct voltage is roughly as shown in the formula expression: $\mathrm{Va}=\frac{1.11\mathrm{Vd}}{\mathrm{Cos\β}}---\left(1\right)$

Va is that voltage of intermediate frequency effective value, Vd are that direct voltage, β are the inversion advance angle in the formula, common β=40 °.Voltage of intermediate frequency Va is generally 1.4～1.5 times of direct voltage Vd under the normal condition.Vd is about 500V, so Va is about 700～750V.In, the voltage of intermediate frequency that obtains by above-listed relation in the large-scale Intermediate Frequency Induction Heating Equipment is often not high enough, in order to improve voltage of intermediate frequency, often adopts the method for capacitance boost, adds one group of electric capacity on inductor more in addition.There is shortcoming in this method: in capacitance boost since capacitor often need add a by-pass inductor every straight effect, this measure causes parasitic low-frequency oscillation easily; In the circuit of capacitance boost, might cause simultaneously the boost capacitor vibration of connecting with the parasitism of load-sensing device.Above phenomenon causes inverter work unreliable even the top is multiple.

The purpose of this utility model is the shortcoming that will overcome prior art, provides in being applicable to, the current source inverter of large-scale Intermediate Frequency Induction Heating Equipment, and it can produce enough high voltage of intermediate frequency and inverter reliable operation.

The technical scheme of taking for achieving the above object:

This Frequency Induction Heating half control bridge current source inverter, comprise inductor, building-out capacitor and the brachium pontis of forming by controllable silicon, inductor and electric capacity form oscillation circuit, direct current is transformed into electric current of intermediate frequency, its design feature is to have only two brachium pontis, feature is that inductor Lr one end connects brachium pontis 1, and the inductor other end connects brachium pontis 2, and brachium pontis 1 and brachium pontis 2 be break-make in turn; Direct current is connected in tap from the inductor coil, forms the half control bridge circuit.

Advantage of the present utility model:

1. this current source inverter can significantly improve voltage of intermediate frequency;

2. owing to do not add boost capacitor, can improve the reliability of inverter work.

The drawing explanation:

Fig. 1 is existing current source inverter basic circuit diagram;

Fig. 2 is the basic circuit diagram of the utility model example 1;

Fig. 3 is the basic circuit diagram of the utility model example 2;

Fig. 4 is the basic circuit diagram of the utility model example 3;

Further specify technical scheme and embodiment with reference to accompanying drawing:

Shown in Figure 1, be the prior art circuits schematic diagram.It has four brachium pontis, and the power supply direct current is by brachium pontis 1 and 3 and brachium pontis 2 and 4 break-make in turn, and then electric current flows through whole inductor coil (load) in turn in opposite direction, is transformed into electric current of intermediate frequency through the oscillation circuit of capacitor C and inductor Lr formation.

Example 1:

As shown in Figure 2.Pick out electric wire from the inductor coil centre cap and pass through direct current.Brachium pontis 1 and 2 is the break-make direct current in turn, makes direct current flow through the left half of and right half of of inductor respectively, and two one side of something take turns to cause the vibration of the oscillation circuit that capacitor C and inductor Lr form by electric current, produce intermediate frequency.Exchange total voltage in the load as shown in the formula expression: $\mathrm{Va}=\frac{2.22\mathrm{Vd}}{\mathrm{CosB}}---\left(2\right)$

It exceeds one times than voltage of intermediate frequency shown in (1) formula, and promptly when direct voltage Vd=500V, Va can reach 1400～1500V.

Example 2:

Further improve voltage of intermediate frequency if desired, can adopt circuit as shown in Figure 3.It is at the inductor coil centre cap, and the left and right side that is symmetrical in hub of a spool respectively tap respectively insert a diode 5 and 6.Draw two half-waves of direct current respectively by these two diodes.Direct current is not to flow through inductor half like this, but only flows through a bit of inductor coil basically.So what the voltage of intermediate frequency on the whole inductor will be than shown in (2) formula is higher.

Example 3:

In large-scale intermediate frequency induction heating power supply, adopt two groups of rectifier bridges, by the power supply of 12 arteries and veins, to solve harmonic pollution to electrical network.Can adopt schematic circuit shown in Figure 4.Vd wherein _AAnd Vd _BBe two groups of identical DC power supply voltages independently separately, connect the half control bridge circuit with example 1 respectively, these two groups of circuit by the inductor series connection together.This moment brachium pontis 1 _AWith 1 _BThe while break-make, brachium pontis 2 _AWith 2 _BThe while break-make; And brachium pontis 1 _AWith 2 _A, 1 _BWith 2 _BBreak-make in turn then.Like this, the voltage of intermediate frequency ratio 1 in the whole load is doubled, promptly when Vd=500, two groups of half control bridge inverter circuit are powered altogether to a load, can produce voltage of intermediate frequency Va=2800～3000V.Similar fashion also extends to three or more half control bridge inverters and powers to a load, produces higher voltage of intermediate frequency, to satisfy the needs of large-scale Intermediate Frequency Induction Heating Equipment.Similar fashion also extends to the occasion of example 2.

Claims (4)

1. Frequency Induction Heating half control bridge current source inverter, comprise inductor, building-out capacitor and the brachium pontis of forming by controllable silicon, inductor and electric capacity form oscillation circuit, direct current is transformed into electric current of intermediate frequency, it is characterized in that inductor Lr one end connects brachium pontis (1), the inductor other end connects brachium pontis (2), and brachium pontis (1) and brachium pontis (2) be break-make in turn; Direct current is connected in tap from the inductor coil, forms the half control bridge circuit.

2. Frequency Induction Heating half control bridge current source inverter according to claim 1 is characterized in that picking out electric wire from the centre cap of inductor coil, and inductor coil left side one side of something and right one side of something pass through direct current in turn.

3. Frequency Induction Heating half control bridge current source inverter according to claim 1, it is characterized in that respectively connecing a diode (5), (6), draw direct current two half-waves respectively by these two diodes from the left and right side tap that is symmetrical in inductor coil central authorities.

4. according to claim 1 or 2 or 3 described Frequency Induction Heating half control bridge current source inverters, it is characterized in that two identical and independently DC power supply power respectively to two half control bridge circuits, they are cascaded by inductor; Brachium pontis 1 _AWith 1 _B, 2 _AWith 2 _BWhile break-make, and brachium pontis 1 _AWith 2 _A, 1 _BWith 2 _BBreak-make in turn.

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