SU411635A1 - - Google Patents

Description

one

The invention relates to interrupters which allow the conversion of a constant voltage into a series of rectangular voltage pulses of a U-shape with an adjustable duty cycle.

Breakers are known that contain a power thyristor and a switching circuit made up of a capacitor and throttles made on a core with a rectangular hysteresis loop, with two interconnected windings, one of which is connected to a power source through a capacitor. However, in such interrupters, the shape of the output voltage pulse is different from the rectangular one, due to the transformation of the voltage change on the switching capacitor into one of the chokes, which is not connected to the switching capacitor.

In order to provide a U-shaped output voltage pulse in the proposed chopper, said throttle winding is connected to another winding opposite and additionally connected through the thyristor to the power source, and one of the capacitor plates is connected to the common point of the throttles windings.

FIG. 1 is given the scheme described breaker; in fig. 2- magnetic characteristic of the core Drossel.

Thyristor 1 interrupter connected by an anode

to the positive power supply bar 2, and the cathode to the beginning of the winding 3, the throttle 4, the end of which is connected to the end of the winding 5. The beginning of the winding 5 through the load 6 is connected to zero

food bus. The common connection point of the windings 3 and 5 is connected to the bottom plate of the capacitor 7, the top plate of which is connected to a positive power source.

The breaker works as follows.

Nris turning on thyristor 1 capacitor 7,

previously charged before the supply voltage E

polarity shown without brackets (see

FIG. 1) turns on parallel to the winding 3. Under the action of the voltage on the capacitor 7 applied to the winding 3, the operating point on the magnetic characteristic of the core of the throttle (see Fig. 2), having been with until the moment of switching on the thyristor - {- Vg moves in the direction of -V. In this case, a voltage is applied in the winding 5 of the drossel 4, which acts counter voltage on the winding 3. If the coefficient

T77

transformations (-) between windings 3 and 5

is equal to one, the voltage across the load does not depend on the change in voltage on the capacitor 7 and is equal to the supply voltage E. As the capacitor discharges, the rate of change in induction in the core of the throttle decreases. For energy reasons, the parameters of droplets 4 and load 6 are chosen such that by the end of the full discharge of the capacitor, the operating point on the magnetic characteristic does not reach negative saturation (-BS). In this case, provided that the number of turns of the winding 5 is greater than the number of turns of the winding 3, under the action of the voltage of the power source applied to the winding 5, the reverse reversal of the core of the throttle 4 to the + 5g side begins, and the capacitor begins to recharge with the polarity shown in brackets (see fig. 1). At this stage of work, the chopper is induced in a winding of 3 emf. acts counter voltage on the winding 5. When the operating point on the magnetic characteristic reaches positive saturation (+ 5g), the recharged capacitor 7 is connected through the low resistance of the winding 3 in parallel to the thyristor 1 and turns it off, recharging then the load current to the supply voltage E.

Thus, in order to eliminate the negative saturation of the core of the throttles, the transformation ratio of windings 3 and 5 must be less than unity and, therefore, it is impossible to achieve full compensation for voltage variations on capacitor 7. Practically, the transformation ratio of windings 3 and 5 can be selected in the range of 0, 9-0.95, which significantly improves the shape of the output voltage pulse, bringing it closer to U-shaped. With a transformation ratio of windings 3 and 5 equal to or greater than one, only an oscillating recharge of the switching capacitor is possible, which is due to the operating point on the magnetic characteristic of negative wiring and the appearance of large charging currents of the switching capacitor, deteriorating the energy performance of the chopper.

Subject invention

A breaker containing a power thyristor and a switching circuit made up of a capacitor and throttles, made on the core with a rectangular hysteresis loop, with two connected dbmotki, one of which through a capacitor is connected to a power source, characterized in The U-shaped pulse of the output voltage, the indicated winding of the throttle is connected with the other winding of the counter and additionally connected through the thyristor to the power source, and one of the capacitor plates is connected to boiling point of the choke coils.

f

t / g .;