SU1483541A1 - Protection unit - Google Patents

Abstract

The invention relates to the field of electrical engineering, in particular to relay protection against overload in the load circuit. The purpose of the invention is to simplify the protection unit. This goal is achieved by connecting the free output of the diagonal of the measuring bridge to the output of the switching element 16 of the actuating unit 12 to ensure that the protection unit is held in the actuated state, since both half-shoulders are disconnected from the power source, and the necessary holding potential is created by supplying a corresponding bias to the input of the differential amplifier 8 through a resistor 11 from the input power bus, since and the differential amplifier 8 and the measuring bridge are powered by the input voltage, then all the changes in the input voltage occur symmetrically and the differential amplifier 8 does not change its state under the influence of changes in the feed voltage. 2 Il.

Description

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The invention relates to electrical engineering and can be used both separately and as part of a secondary power source as an automation element that cuts off the load circuit from the source when the consumed current is exceeded by the load from the source.

The purpose of the invention is to simplify the protection unit.

FIG. 1 and 2 are diagrams of a block of protection with different transistors in executive units.

The protection unit contains the first and second poles 1 and 2, respectively, of the power source, a measuring bridge of resistors 3-6, a current sensor 7, a differential amplifier 8 The output of the measuring bridge is connected to the inputs of a differential amplifier 8 through resistors 9 and 10, and the half-arm output of the measuring bridge the bridge of resistors 5 and 6 is connected to the pole 1 of the power supply (power bus) through a resistor 11. The output of the differential amplifier 8 is connected to the input of the execution unit 12, made on resistors 13, 14, a trasistor 15, switching electr ments performed E a relay 16 with normally closed contact 17 and a diode 18. The load 19 is connected between the poles of the power source. Between the positive power bus and the half-arm output of the measuring bridge, resistors 3 and 4 can be connected in series with a circuit from the closing contact 20 and a capacitor 21, in parallel with which a resistor 22 is connected.

The protection unit operates as follows.

When power is applied to the poles 1 and 2 along the load circuit 19 and the current sensor 7, the operating current flows. At the outputs of the measuring bridge, a voltage is formed that has a higher level in the half-shoulder of resistors 3 and 4 than at the output of the half-shoulder of resistors 5 and 6 and resistor 11. At the output of the differential amplifier 8, the voltage is low and executive unit 12 is in a de-energized state. This state is maintained until

one when the operating current does not exceed the allowable value.

When the operating current exceeds the allowable value at the output of half

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The measuring bridge arm of resistors 5 and 6 becomes higher than the half-arm output of the measuring bridge of resistors 3 and 4. At the output of the differential amplifier 8, a voltage level appears that causes the opening of the transistor 15, as a result of which the relay coil 16 is connected between the power leads, pin 17 opens, de-energizes the load circuit 19 and the measuring bridge on the resistors 3-6. However, due to the presence of a resistor 11 at the output of the measuring bridge half-arm, the resistors 5 and 6 maintain a voltage level that keeps the executive unit 12 in the de-energized state, which de-energizes the load circuit 19.

To return the device to the initial state, contact 20 is closed, and the current pulse through the capacitor 21 provides a voltage at the output of the bridge half-arm of resistors 3, 4, which is higher than the output of the bridge half-arm of resistors 5 and 6. This leads to the appearance at the output of the differential level amplifier, at which the executive unit 12 is de-energized. Contact 17 of relay 16 is closed, and if everything is normal, this state is held, if overcurrent is not eliminated, then de-energization of load circuit 19 will occur.

When contact 20 is opened, capacitor 21 is discharged through resistor 22. Diode 18 and resistor 14 bias transistor 15 to lock it securely

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Claims (1)

Invention Formula A protection unit containing a current-to-voltage converter made in the form of a current sensor and a measuring bridge, the first output of the current sensor is connected to the first pole of the power supply, the second output is intended to be connected to the first load terminal, to the output of the current sensor is connected one output of the diagonal of the measuring bridge , the measuring diagonal of which is connected to the inputs of the differential amplifier, the output of which is connected to the input of the execution unit connected between the poles of the power source, the first terminal wiping member actuating unit connected to the second pole of the power source, a second terminal intended for connection to a second terminal of the load resistor, characterized in that, for the purpose of simplicity, a resistor is included between one of the poles of the power supply and the half-arm output of the measuring bridge connected to the direct input of the differential amplifier, with the other output of the diagonal of the measuring bridge connected to the second output of the switching element of the control unit. Compiled by L.Voropaeva Editor M.Tsitkina Tehred l. Serdkzhova Order 2842/50 Circulation 607 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 Production and publishing plant Patent, Uzhgorod, st. Gagarin, 101 G, „, P FIG. 2 Proofreader N.Korol Subscription