SU1415316A1 - Device for temperature protection of electric motor - Google Patents

Abstract

The invention relates to the field of electrical engineering and can be used to protect electrically major, responsive to current overloads and deviations from normal temperature. The aim of the invention is to ensure noBbiujenne accuracy by compensating for the dynamic linearity of the posistors. The goal is achieved by introducing a pulse generator 7, a duty ratio controller 8, a resistor 9, a first and 4 and a second 5 filters, an adder 6 and a key 12 into the device. Due to the additional heating of the posistor with a pulse current, the duration of which is controlled in the duty cycle controller 8 and directly proportional to the magnitude of the load current, compensates for the dynamic error of the posistor at any rate of rise of the winding temperature, depending on the load of the electric motor. 5 il. (O (L was eating :) O5

Description

I. the invention relates to .txtrotch hnike and may be nciio.TbaoEUiHO to protect:) electrical systems that react to shock loads and deviations from the normal temperature.

The aim of the invention is to improve the accuracy by compensating for the dynamic but | -replicacy of the nozzetors.

FIG. 1 shows a block diagram of the device; in fig. 2 5 time diagrams of voltages and currents of pa elements of the circuit. We are when the device is operating.

The device consists of a thermal sensor, full on the nose. Connectedly, 1P1 | x Nosistors 1, which are installed in the frontal parts of the motor windings. In the two phases of the motor windings there are terminals for connecting the primary windings of the two transformers, respectively, of the current, the secondary windings 2 and 3 of which are connected respectively to the inputs of the first 4 and V D filters, the outputs of the latter are connected to the I (accumulator (i. Pulse-rcne ) aio) 7 is connected to the first input terminal of the duty cycle of the 8; the second input of the Topoi o is connected to the output of the adder 6. B1,1 the inputs of the duty cycle adjuster 8 are connected to the posistor 1, the first of which is connected through a resistor 9, and the second directly. The 11 telio terminals of the thermal sensor and from the posistor 1 are connected after-D () Vage. The diode K) and the capacitor II connected to each other. 1 aralle, so-called ropv node, key 12 connected to the base of the power. 1) 1m body 115 and the commutation apparatus 14.

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Immunity1) 1Y generator 7 produces an imp, directly from the shape of the positive polarity of the frequency and then read it (Fig. 2). Voltage pulses are supplied from the output of the generator 7 by a pa () the input of the regulator 8 of the duty cycle, while in the thermosensitive circuit, there is a nieii of sequentially connected nozzles 1 and a resistor 9 connected to the outputs of an nm volt of torus 8 duty cycle, flowing imnu.pnny current (Fig. 3). which creates a cooTBCTCTBenfH) voltage drop on P-shafts 1 and Estors 9.

The fall of the cable joint, the electrical resistance, to the electrical resistance of the nozzles 1, is fed to the co-detector 11 through the diode K). At one time, the second input of the duty ratio controller 8 is supplied from the sum of the controller (), coming from the secondary first-time () 2 n BTOpoi o 5 transformer currents, respectively, through the first 4 and second n filters, proportional to the sum of the currents in () the windings of a zaniped electric motor | at.t., almost allows it to be more than the point (j) oi) Mn- (un)) (111) and the second signal at the second input of the rotary ratio adjuster b.

Ianr zhe | ie, postunak) P1ee with sumgo and) c () at the second entrance of the river .; . then) and H duty ratio.

0

five

0

five

0

five

It is controlling for it and is influenced by the duration of the current pulses flowing in the thermosensitive circuit consisting of series-connected posistor 1 and resistor 9. As the load increases, the motor consumes its current and increases . The pulling voltage and duration of the current, Proyayun1, it in the heat-sensitive circuit (Fig. 4 and 5).

With a minimum current in the motor windings and small overloads (for example, up to 21N), when the speed of the motor windings increases, Ia, a thermal current flows through the temperature sensitive circuit of the posistor 1 and resistor 9, which does not cause the self-heating of the resistors 1. Dynamic posistors error 1 in this case, the case is practically absent, and their thermal state, and accordingly, the electrical resistance, are determined by the thermal state of the motor windings.

When the battery packs do not regulate, for example, more than 21N, when the rate of increase in the temperature of the windings increases noticeably and the dipamic error of the posistor 1 also increases, the duration of the current pulses flowing in the temperature-sensitive circuit increases proportionally to the current load of the electric motor, and as a result, an additional charge occurs} | th heating of the posistor 1, which ensures their accelerated response and compensation of the dynamic error (inertia of the posistor). The value of the equivalent of a current flowing in a temperature-sensitive circuit is determined by the expression

and „/ ..

 R, K, T

0

five

where L lin Ri

power supply voltage; cyMMapiioe posistor resistance;

 resistance of resistor 9; - the duration of the current pulse flowing in the heat-sensitive circuit (Fig. 2);

Tperiod current pulse (Fig. 2).

When the temperature response of the posistor 10 is reached due to their heating from the motor windings (with a slight P1IH overload of the electric motor up to 21 N) or their combined heating from the winding of the electric motor and due to the current, Q flow) in the thermally sensitive circuit ( when the motor overloads and currents are more than 2IH), the electrical resistance of the posistor 10 increases dramatically, which leads to an increase in the drop in voltage and increase in voltage across the capacitor 1 1 according to the expression

UJ I-L HN

R. + R

If the voltage on the capacitor 1-1 reaches the key trigger threshold, the actuator 13 is triggered, acting on the switching device 14, and the superheated electric motor is disconnected from the power source. The trigger voltage of the switch 12 is determined only by the resistance of the posistor I and does not depend on the magnitude of the current in the temperature-sensitive circuit.

In the mode of frequent frequent starts (which is typical of many electric drives), when the electric motor is already sufficiently heated, due to the thermal effect of the equivalent current A flowing in the thermally sensitive circuit, early operation of the posistor 1 may occur, although the windings of the electric motor exceed the permissible for this class of insulation of

In order to eliminate the advance response of the fins 1, filters 4 and 5 provide an increase in control of the signal on the second input of the duty ratio controller 8, coming from the adder 6, depending on the time of the starting current.

In the proposed device, in comparison with the known, greater accuracy is achieved in the protection of an electric motor due to the flow of a pulsed current built in the motor winding, proportional to the current in the phase windings, thereby compensating for the dynamic error of the posistor at any of the sko) os0

five

0

five

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t x increase winding temperature, depending on the load of the electric motor.

Claims (1)

Invention Formula A device for the temperature of the electric motor, containing a thermal sensor, made on series-connected posistor, which are installed in the frontal parts of the motor windings, parallel to the terminals of the thermal junction are connected in series a diode and a capacitor, two current transformers, the primary windings of which contain terminals for connection to the corresponding motor power phases as well as the executive body, characterized in that, in order to improve accuracy by compensating for the dynamic posistors, a pulse generator, a duty cycle controller, a resistor, the first and second filters, an adder and a key were added to the device, and the pulse generator was connected to the first inlet regulator the first input of which is through a resistor, and the second is directly connected to the terminals of the thermal sensor, the secondary windings of the current transformers are connected to the first and second filters respectively, the outputs of which are connected to the inputs of the adder, the output of the adder is connected to the second input of the register with importance. couple. 1. 1e, 1рпо to () ndensato n is connected to, 1yuch, the output of which is connected to the executive module.