SU439794A1 - Device for switching transformer taps - Google Patents

Description

Devices for switching transformer leads are known, containing keys, for example, from anti-parallel-connected thyristors, where the key, the switching tap with minimum voltage is uncontrolled and closes with the switching organ, and the control circuit of each of the other keys contains a pulse shaper synchronization and measuring element with a DC output and a source of reference voltage at the zener diode.

In order to obtain a small distortion of the output voltage and low level of radio interference in the proposed device, the control circuit contains Schmitt triggers according to the number of pulse shapers, whose inputs are combined and connected to the measuring unit, and the output of each Schmitt trigger trigger is connected to the input of the corresponding driver.

Each pulse shaper is made on two blocking generators according to the number of thyristors in the key, which allows the device to work for any type of loading.

The synchronization unit is for all controllable switches and contains a current transformer included in the power circuit, l voltage voltage transformer, the secondary windings of which through diodes are connected to the input of each blocking generator so that the blocking voltage is supplied to the input of the blocking generator half-periods of current and voltage of the corresponding thyristor.

FIG. 1 is a schematic diagram of the device described; in fig. 2 - the same, with current and voltage synchronization.

The adjusting taps of the transformer 1 are switched by keys consisting of counter-parallel connected thyristors. Switch 2, the switching tap corresponding to the minimum output voltage of the transformer, is uncontrolled. On the thyristors of this key, at the beginning of each half-cycle of current, the switching-on organ 3 is supplied with switching pulses. Keys 4 and 5 are controllable, i.e. can be included

and are disconnected depending on the output voltage 1 / output- The turn-on pulses on the thyristors of the keys 4 and 5 are supplied from the formers 6 and 7 of the pulses, whose operation is synchronized with the input voltage of the transformer with the help of the synchronization authority 8. The pulse formers are triggered by signals from the corresponding Schmitt triggers 9 and 10. The combined inputs of these triggers are supplied with the voltage difference between the rectifier 11 with the filter connected to the output of the transformer 1 and the zener diode 12. The Schmitt grinders are set up so that the difference between their response and release voltages is the same. The levels of the operating level and of the triggering of the trigger 9, which controls the key 4, are shifted upwards relative to the corresponding levels of the trigger 10.

When the trigger is triggered, its output signal disappears, the driver of the pulses stops its operation and at the end of the current period the corresponding key is locked. When voltage UB is input to the device, key 2 opens, and then, if the corresponding signals arrive, keys 4 and 5. When opening key 4, the thyristors of key 2 are locked by reverse voltage applied to them from transformer 1 through key 4. When opening key 5 is locked key 4. To prevent false unlocking of keys 2 and 4, the switching pulses on their thyristors should be fed only in those half-periods when Direct anode voltage coinciding in phase with the input voltage is applied to the thyristor.

At the maximum value of voltage t / Bx, the voltage Ug at the input of the triggers is alarmed by their response levels, the triggers are in the activated state, the keys 4 and 5 are locked. Voltage The UHV is applied via switch 2 to the maximum number of turns of the primary winding of transformer 1, and the output voltage L / out is only slightly higher than its nominal value.

Decreasing the voltage UES. To release level of trigger 9, key 4 is turned on, and key 2 is locked. Voltage (Vyvh increases abruptly. Voltage C / vtx also increases, but its maximum value should be less than the trigger voltage 9 to avoid the reverse (switching keys 4 and 2. With a further decrease in the voltage, trigger 10 releases, key 5 turns on, and key 4 is locked. After switching, the input at the trigger input also in order to avoid reverse switching should not reach the trigger trigger level 10.

As the voltage increases (ohv, the adjustment process proceeds, in reverse order: first, trigger 10 is activated and key 5 is locked, key 4 is unlocked, then trigger 9 is activated and keys 4 and 2 are switched.

The device can also be configured with keys in the secondary winding.

If the device operates on a load with inductive or capacitive response, when the current lags behind or leads the voltage, then synchronizing the operation of the pulse shapers only by voltage or current, Pelz avoids short circuits of the transformer 1 taps through the thyristors of the keys. To eliminate this, you must serve them

The switching pulses of the thyristors of keys 4 and 5 only at those times of the corresponding loluperiods, when the current and voltage are the same. For this purpose, in 1 session, there is a set of users and Hroppzac1 and Shapes formario; atsle M1 current pulses H. MOTION FROM 1NXRO IZHRITSES INCLUDE in that the pulse formers from the synchronization body are supplied with a locking

voltage at those moments of the period when the formers do not have to work. The signal from the Schmitt trigger can start the pulse shaper only when the current and voltage are odd; new sign.

Each pulse generator (see Fig. 2) consists of two blocking generators, each of which controls one thyristor. The current is synchronized by a current transformer 13 connected to the power circuit of the device, and the voltage synchronized by a transformer 14 connected to the input of the device. The secondary windings of transformers 13 and 14 through diodes 15 are connected to the input of each blocking generator. The diodes and the windings are turned on so that the blocking generator 16, which includes the thyristors of the keys 4 and 5 working in negative half-periods, is supplied with a blocking voltage in the positive half-periods

current and voltage, and on the 17-B block generators - B negative semi-periods.

Subject invention

Claims (3)

1. A device for switching traction transformer taps, containing keys, for example, from head-on switching on full thyristors, where the key that switches the tap with the minimum voltage is uncontrollable and is closed with the aid of the switching element, and the control circuit of each of the other keys contains a pulse shaper, a synchronization body and a measuring element with an output at a constant current and a source of reference voltage on the zener diode, characterized in that in order to obtain a small distortion the output south voltage and low level of radio interference; the control circuit contains Schmitt triggers by the number of pulse shapers, whose inputs are combined and connected to the measuring unit, and the output from Schmitt triggers is connected to the entrance of the corresponding driver. 2. The device according to claim 1, characterized in that, in order to ensure the possibility of working under any type of load, each pulse shaper is made on two blocking generators according to the number of thyristors in the key. 3. The device according to PP. 1 and 2, characterized in that the synchronization body is common to all controllable keys and contains a current transformer included in With a circuit, and the transformer is the same). the secondary windings of which through Diodes are connected to the input of each blocking generator, so that the block voltage is applied to the input of the blocking generator in the non-operating half-periods of the current and voltage of its thyristor. L