SU1534619A1 - Device for overload protection of transistor inverter - Google Patents

Abstract

The invention relates to electrical engineering and can be used for protection against overload and short-circuiting of the output circuits of a transistor inverter operating at a highly variable load. The purpose of the invention is to increase the stability of the re-start delay time. The introduced single-junction transistor 2, together with the capacitor 3 and the resistor 4, forms a pulse generator with a high stability of the pulse-following period used to turn on the device again. 1 il.

Description

The invention relates to electrical engineering and can be used To protect against overload and short circuit of the output circuits of the transistor - $ Logo of the inverter operating on a sharply variable load.

The purpose of the invention is to increase the stability of the delay time reclosing. IQ

The drawing shows a diagram of a device for protecting a transistor inverter from overload.

The device consists of a pulse generator made on a single-junction transistor 2, a capacitor 3, a resistor 4, a shunt transistor 5, the collector and emitter of which are connected respectively to the anode, the cathode of thyristor 6 and to the input 20 terminals of inverter 7, transistor 8, / of which the emitter is connected with the positive bus of the auxiliary source of quoting, the collector is connected to the second gap of a single-junction transistor 2, 25

The gap is connected through a resistor 9 to the anode. thyristor 6, overload sensor 10, the output terminals of which are connected to the cathode and the control electrode of the thyristor 6, and the input terminals are ₃ θ to the output of the inverter 7.

The device operates as follows.

In the steady state, when there is no overload at the output of the sensor 10 [the overload signal to the thyristor 6 and [the transistor 5 is closed, the input of the inverter 7 is open and the inverter is operating in nominal mode, and its output voltage is rated. Thyristor 5 ₄ q and thyristor 6 are closed, because there is no current in the base of transistor 8 and it is closed. The supply voltage of the pulse generator 1 is zero, the capacitor 3 is discharged, the current in the base of transistor 45 of torus 5 is zero.

When a signal appears at the output of the overload sensor 10, the thyristor 6 opens and shunts (closes) the input of the inverter 7, as a result of which the voltage at the output of the inverter 7 becomes zero. At the same time, current will flow through the opened thyristor 6, resistor 9, and the base-emitter junction of transistor 8. The transistor 8 will open- $$ and the voltage will be supplied to the power output of the pulse generator 1. The charge of the capacitor 3 through the resistor 4 will begin. When the voltage on the capacitor 3 reaches the threshold of the single-junction transistor 2, a current pulse will pass through the base-emitter junction of the shunt transistor 5, which will open this transistor. The opened transistor 5 shunts the thyristor 6, the current through it will stop and it will go into a non-conductive state. When the capacitor 3 is discharged and the current pulse through the base-emitter junction ends, the shunt transistor 5 will close, which will cause the closure of the additional transistor 8 and the voltage at the power output of the pulse generator 1 will be reduced to zero. At the moment of closing of the shunt transistor 5, since the thyristor 6 was closed earlier, the input of the inverter 7 will open, it will turn on and the rated voltage will appear at its output. If at this moment the overload at the output of the inverter remains, then at the output of the overload sensor a signal appears again that opens the thyristor 6, and the process of turning off the inverter will be repeated.

Since each cycle of the device for protection ends in the fact that the capacitor 3 is completely discharged, and begins with the fact that the completely discharged capacitor 3 is charged to a certain value, the time for the inverter to turn on again, which is equal to the sum of the times of the indicated processes of discharge and charge of the capacitor 3, in the proposed device is stable and independent of the duration of the overload and the moment of its occurrence.

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Claims (1)

Claim A device for protecting the transistor inverter from overload, containing an overload sensor, the output of which is connected to the thyristor control electrode, the anode and cathode of which are designed to be connected in parallel with the input terminals of the transistor inverter, the first transistor, emitter and collector of which are connected respectively to the cathode and anode of the thyristor, the second a transistor, first and second resistors, each of which is connected to the base with a first output, of the corresponding transistor, a third resistor, capacitor and auxiliary power supply, the first pin5 1534619 connected to the cathode of the thyristor, characterized by the fact that, in order to increase the stability of time! re-enable delays, a single-junction transistor is introduced, the first base of which is connected to the base of the first transistor and connected through its first resistor to its emitter, connected through a capacitor to the single-junction transistor emitter, connected through a third resistor to its second base connected to the collector of the second transistor, a second transistor having a conductivity type 5 opposite to that of the first transistor is connected to an emitter. the second output of the auxiliary power supply, · IQ and the base is connected to the second output of the second resistor.