SU868911A1 - Device for temperature protection of electric equipment - Google Patents

Description

one

The invention relates to electrical engineering and can be used for temperature protection of electrical installations.

A device of similar purpose is known l.

A significant drawback of the device is the complexity of manufacture, configuration and operation. This is due to the complexity of the blocking unit of the start button, the use of the measuring bridge, and the limited choice of nominal value for thermistors, the resistance of which determines the thyristor control current.

In addition, the sensitivity of this device is low and depends on the value of the control current of the thyristors. This may lead to the appearance of a constant component in the supply circuit of the winding of the magnetic starter.

The closest technical solution to the present invention is a device containing a power source, to the terminals of which a voltage divider with a thermal sensor in one arm is connected, a transistor switch, the input of which is connected to the output of a voltage divider and actuator L2.

A significant disadvantage of this device is the complexity of manufacturing and low reliability of operation due to the lack of control over the operability of the earthing of the installation case and the need to use two wires to connect the temperature sensors to the input of the device.

The purpose of the invention is to simplify the device and increase the reliability of its operation.

The goal is achieved by the fact that the actuator is connected to the clamping power source through

15 resistors, and its input is shunted by a collector-emitter junction of the transistor. .

In addition, a second voltage divider is additionally introduced into it,

20 connected to the power supply and the second transistor switch, the input of which is connected to the output of the second voltage divider and the emitter of the transistor to the output of the first divider

25 voltage, while the collectors of both transistors are interconnected and connected to the second output of the first voltage divider.

Claims (2)

The drawing is a coziness scheme30. . The device comprises an actuating element 1, a power source 2, a voltage divider 3 with a thermal sensor 4 in one arm is connected to the terminals of which, and a transistor switch 5 / whose input is connected to the output of the voltage divider. An executive element is connected to the power supply terminals through resistors b and 7 and is shunted through a diode 8 by a collector-emitter junction of a transistor switch, the collector of which is connected via a second diode 9 to the output of the second arm 10 of the voltage divider. A second voltage divider 11 connected to the power supply terminals and a second transistor switch 12, the input of which is connected to the output of the second voltage divider, and the collector-emitter junction through the second diode 9 with the output of the second arm 10 can additionally be introduced into the device. first divider 3 voltage. Current transformers can be used to reduce the dynamic error of the device as power supply 2. The device works in a dim way. In the initial state, the voltage at the output of the power supply 2 is zero. The executive element 1 is disabled, the transistor switches 5 and 12 are closed. The sensor 4 is installed on a controlled installation, which is de-energized. Current transformers, the primary windings of which are included in the power circuit of the installation, are used as the power source 2. When the power source 2 is turned on, the device is initially energized using the control button. Actuator 1 is turned on and gives a command to turn on the installation. The voltage from the current transformers appears at the output of the power source 2, therefore, the actuator 1 and the installation remain in the on state. The transistor switches 5 and 12 remain closed, as the potentials of their emitters are higher than the potentials of the bases. In the event of an overload of the installation, the heating of its elements and, accordingly, the temperature of the thermal sensor 4 increase. At the same time, the voltage at the output of the power supply 2 increases, however, when the mass overload increases, the voltage does not have a significant effect on the thermal heating 4, therefore the temperature of the latter determined by the temperature of the elements of the installation. When it exceeds the value of the response temperature of the sensor 4, its resistance increases. The base potential of the transistor switch 5 is higher than the potential of the emitter, so key 5 opens and shunts the actuator 1. The latter turns off and forms a command to turn off the device, which can be reclosed when the installation elements are cooled to their nominal value. In the event of a significant overload of the installation, for example, when the engine research institute overturns, the voltage at the output of power supply 2 increases sharply, which leads to additional heating of the thermal sensor 4. If the overload is not removed, the device provides a forced shutdown of the installation. This compensates for the dynamic error of the device. When the thermal sensor 4 breaks, transistor switch 5 opens, disconnecting the actuator 1. When the thermal sensor 4 short-circuits, transistor switch 12 opens, which also shunts the actuator 1 with its collector-emitter junction, disconnecting the latter. Due to the exclusion of their thyristor circuit, simplification of the rectifier, the reliability of the device operation has increased, and the connection of a single clamp of the thermal sensor with the installation case greatly simplifies the installation of the device. Claim 1. A device for thermal protection of an electrical installation, containing a power source, to the terminals of which a voltage divider with a thermal sensor in one arm is connected, a transistor switch, the input of which is connected to the output of a voltage divider and an actuator, characterized in that valuing the device and improving its reliability, the actuator is connected to the power source through resistors, and its input is shunted by a collector-emitter junction of the transistor. 2. The device according to claim 1, about tl and which is so that, the second divider is reintroduced into it eg. connected to a power source and a second transistor switch, the input of which is connected to the output of the second voltage divider and the emitter of the transistor to the output of the first voltage divider, while the collectors of both transistors are interconnected and connected to the second output of the first voltage divider Sources of information taken into account in the examination 1. Danilov Woy. Thyristor motor overheating protection circuit. Mechanization and electrification of socialist agriculture, 1978, 2, 0.43. 2. Authors certificate of the USSR 357644, cl. H 02 H 7/08, 1972.