IE51256B1

IE51256B1 - Energy recuperation device for an inverter

Info

Publication number: IE51256B1
Application number: IE241080A
Authority: IE
Original assignee: Jeumont Schneider
Priority date: 1979-12-27
Filing date: 1980-11-20
Publication date: 1986-11-26
Also published as: ES8200527A1; JPS56501865A; EP0031780B1; BR8008994A; EP0031780A1; CH643695A5; FR2472871A1; FR2472871B1; WO1981001920A1; IE802410L; DE3069955D1; ES497781A0

Abstract

Simple and economical device allowing the recovery of energy stored by the grid-leak inductances of the electrical machine connected to the thyratron inverter. According to the invention, the device comprises a transformer of which the primary winding (13), in series with at least a switching transistor (14) controlled by the logic (5) of the thyratron inverter, is connected between the terminals of the capacitor (12) in which the energy to be recovered is transferred, and of which the secondary winding (15) is arranged in series with one of the terminals of the direct current source (4) and the corresponding input of said thyratron inverter. Application: control of electric motors.

Description

The present invention relates to inverters which, when connected between the terminals of a direct current source, make it possible to generate an alternating current of variable frequency, and which are intended in particular for controlling the speed of rotation of a rotary electrical machine of the asynchronous type, and it relates more specifically to an energy recuperation device for an inverter of this type. Various energy recuperation inverters have been described, for example, in French Patents Nos. 1,552,477 and 2,515i193j but they have the disadvantage of being of complex construction and expensive in relation to the saving achieved.

The present invention has as its subject an energy recuperation device whose price is low in relation to the saving achieved.

The inverter includes in known manner a capacitor connected between the direct current lines and receiving the energy stored by the leakage. inductance coils of the machine controlled by is switched. If no this energy, a branch this energy, in series of which is controlled trolling the switching the inverter, whenever a transistor device is provided for recuperating containing a resistor dissipating with a thyristor^ the energisation hy the logic system already conof the other switchable components, 51286 is connected in parallel with the capacitor. According to the present invention there is provided a device for the recuperation of energy stored by leakage inductance coils of a rotary alternating current electric machine connected to output terminals of an inverter with transistors, which produces an alternating current of variable frequency and is connected to a direct current source, which inverter includes a logic system controlling the switching of the transistors and a capacitor connected between direct current lines of said inverter and receiving said energy stored by the leakage inductance coils of said machine on each switching through the medium of a diode bridge, which device comprises a transformer whose primary winding, in series with at least one switching transistor controlled by said logic system, is connected between the terminals of said capacitor and whose secondary winding is connected in series between one of the terminals of said direct current source and the corresponding input of said inverter.

The device of the invention may be supplemented by a 2o plurality of branches which make it possible to improve its operation and to avoid the creation of any overvoltage between the terminals of the transistor used.

The invention will be better understood, and other aims, advantages and characteristics of the invention will be seen more clearly, on reading the description which is given below and which is accompanied by two sheets of drawings. s' Figure 1 shows an electrical diagram of an arrangement comprising the inverter and the energy recuperation device, according to a first embodiment of the present invention, Figure 2 shows an electrical diagram of the same arrangement according to a second embodiment of the invention, and Figure 3 shows the diagram of Figure 1, in which certain branches have been added to the recuperation - 5 device in order to improve its operation.

Referring now to Figure 1, which shows hy way of indication a first embodiment of the invention, the inverter comprises six transistors 1, between which the machine 5 is connected in known manner. The inverter is connected to the output terminals of a direct current generator 4, which is generally composed of a controlled rectifier connected in series with an inductance coil to the terminals of an alternating voltage source. A logic system 5 controls the switching of the transistors of the inverter.

A branch comprising a resistor 6 in series with a thyristor 7 is provided in order to avoid any overvoltage between the direct current lines 8 and 9. In addition, two diodes 10 and 11 are connected in series in the lines 8 and 9 in known manner, between the transistor bridge 1 and the diode bridge 2 intended to direct the energy stored by the leakage inductance coils of the machine 5, whenever the transistors 1 are switched, to the capacitor 12 which is connected between the lines 8 and 9.

According to the invention, the device for recuperating this energy includes essentially a transformer whose primary winding 15 is connected in series with at least one switching transistor 14, and whose secondary winding 15 is connected between one of the terminals of the direct current source and the corresponding input of the inverter.

The energy stored, in the capacitor 12 as soon as a voltage appears at its terminals is thus transferred. to a current generator connected in series with the current source 4. Two diodes 46 and 1/ isolate the winding 15 from the current source 4 when the transistor 14 is blocked and there is no recuperation of energy.

The diagram shown in Figure 2 utilises two switch10 ing transistors 14 and 24. The primary winding 15 of the transformer is connected between the common points of, on the one hand, the transistor 14 and the diode 25 which are connected in series in a branch connected between the terminals of the capacitor 12, and on the other hand the transistor 24 and the diode 25 connected in series in a second identically connected branch. In this case the energy is recuperated when the two transistors 14 and 24 are conductive, and conversely the transformer is desaturated by means of the two diodes 25 and 25 when these two same transistors are blocked.

In comparison with the arrangement shown in Figure 1, this diagram has the advantage of utilising transistors of low performance, that is to say less expensive transistors. In fact, they withstand a voltage equal to the value of the peak voltage of the capacitor instead of a voltage of twice that value. - 7 Considering now Figure 3, in which components common to the diagram of Figure 1 bear the same references, it will be seen that two branches have been added to the energy recuperation device.

The first of these branches comprises a second secondary winding 18 of the same transformer, in series with a diode 19, the branch being connected in parallel with the capacitor 12. The purpose of this branch is to desaturate the transformer when the transistor 14 is blocked. It thus makes it possible for the magnetising current to be evacuated automatically and rapidly.

The second of these branches comprises a resistor 20 in series with a thyristor 22 controlled by the logic system 5. This second branch is connected in parallel with the primary winding 13 of the transformer. Its purpose is essentially to reduce the voltage at the terminals of the transistor 14 very rapidly when that transistor is blocked, so as to obtain an excellent duration factor and to dissipate in the resistor 20 the energy stored in the primary winding 13.

In one embodiment,the direct voltage was ahout 700 V and the operating frequency of the device amounted to 2 kHz for a 30 kW machine. Under these conditions the device made a saving of about 10% of the energy con25 sumed.

Although only one embodiment of the invention - 8 has been described, it is obvious that any modification made by those skilled in the art within the spirit of the invention would not go beyond the scope of the present invention. Por example, the secondary winding 15 may be connected in series between the other terminal of the direct current source 4 and the corresponding input of the inverter. Similarly, the recuperation device which has been described above may also be used with a thyristor inverter instead of a transistor inverter. Finally, 1° the motor connected to the terminals of the inverter may equally well be of the asynchronous type as of the underexcited synchronous type

Claims

1. A device for the recuperation of energy stored by leakage inductance coils of a rotary alternating current electric machine connected to output terminals of an inverter with transistors, which produces an alternating current of variable frequency and is connected to a direct current source, which inverter includes a logic system controlling the switching of the transistors and a capacitor connected between direct current lines of said inverter and receiving said energy stored by the leakage inductance coils of said machine on each switching through the medium of a diode bridge, which device comprises a transformer whose primary winding, In series with at least one switching transistor controlled by said logic system, is connected between the terminals of Said capacitor and whose secondary winding is connected in series between one of the terminals of said direct current source and the corresponding input of said inverter.

2. A device as claimed in Claim 1, wherein a first diode is connected in series with said secondary winding while a second diode is connected in parallel with a branch including said secondary winding and said first diode in such a manner as to prevent any circulation of current contrary to the polarity of said source.

3. A device as claimed in Claim 1, which also includes a branch conprising a second secondary winding of said transformer, in series with a third diode, which branch is connected between the terminals of said capacitor in such a - 10 manner as to desaturate said transformer when said transistor is blocked.

4. A device as claimed in Claim 1, which also includes a branch comprising a resistor in series with a 5. Thyristor controlled by said logic system, said branch being connected between the ends of said primary winding.

5. A device as claimed in Claim 1, wherein said primary winding is disposed between the common points of a first switching transistor and a diode, which are connected in series 10 iu a branch connected to the terminals of the said capacitor.

6. A device as claimed in Claim 1, wherein said primary winding is disposed between the common joints of a second switching transistor and a diode connected in series in another identically connected branch. 15

7. A device according to Claim 1, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.