SU1320861A1 - Device for protecting three-phase induction electric motor from two-phase operation and locked rotor operation - Google Patents

Abstract

This invention relates to the field of electrical engineering - to motor protection devices against emergency operation. The purpose of the invention is to increase the reliability and sensitivity of the protection device. The device contains quick-switching current transformers 1, 2, 3, which, through the inverter 7, the pulse sequence control unit 8, the detuning unit 9 from the starting mode, the inverter 10, the integrating unit 11, the threshold amplifier unit 12 acts on the actuator 13 and turns off motor from the network at the time of the occurrence of a two-phase engine Preventing a false engine shutdown is achieved by setting up circuit elements that exclude the supply of voltage to the executive unit 13. 1 sludge. (L

Description

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11320861

The RFC declaration relates to electrical engineering, namely, devices for protecting the motor from emergency operation.

The purpose of the invention is to increase the reliability and sensitivity of the protection device.

The drawing shows a circuit diagram of the device. The proposed device consists of fast-current transformers 1-3, load resistors 4-6, three-phase half-wave puller 7, block 8 for controlling the sequence of current pulses, block 9 for detuning from the starting mode, inverter 10, made on the element I - NOT, the integrating unit 11, the threshold amplifying unit 12, the actuator 13s of the power unit 14, the diodes 15 and 16.

The device works as follows

When starting the motor, current transformers 1-3 enter saturation and at the output of a half-wave Three-phase rectifier 7 voltage pulses with a frequency of 150 Hz appear. The constant component voltage decreases to zero. The pulses arrive at the input of the block 8 of the control of a sequence of current pulses. The resistor 17 and the zener diode 18 limits the amplitude of the input voltage to a logic level of 1. The inverter 19, made on the element AND- NOT, begins to periodically switch. From the output of the inverter 19, the pulses arrive at the first input of the detuning unit 9 from the starting mode, consisting of a resistor 20, a condensate 21, and an IS-NOT 22 element.

The second input of the log: the IS-NE 22 is connected in parallel to the capacitor 21, which is charged by positive pulses through d-15 and resistor 20. The time it takes for the capacitor 21 to charge to logic level 1 is the detuning time from the starting mode. As long as the capacitor 21 is not charged at the second input of element 22, there is a logic level O, therefore, at the output, the level of logic 1 is independent of the change in the logic level at the first input. As soon as the engine starts, the currents in the primary windings of the transformer

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Gender: Female; Current output;

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current tori are reduced and they go out of saturation mode. On the input of a three-phase half-wave rectifier 7, the constant component increases to logic level 1. Logic level 1 appears at the input of the inverter 19 of the control unit of the pulse current sequence, and logic level O appears at the output. By this time the capacitor 21 of the detuning unit from the starting one the mode is charged to logic level 1. Therefore, the output of element 22 is logic level 1, and the output of inverter 10 is logic level O. The device switches to monitoring mode.

When a two-phase operation occurs, the constant constituting the output of the three-phase half-wave rectifier 7 is reduced to zero. Inverter 19 starts to periodically switch and pulses with a frequency of 100 Hz from its output go to the first input of element 22. Since the second input of element 22 is logical 1, the pulses go to inverter 10 and then to integrated block 11. As soon as the terminal on the integrate unit reaches a certain value., The threshold amplifying element 12 connects the executive organ 13, which disconnects the electric motor from the mains. In this case, the power supply voltage disappears, the capacitor 21 of the detuning unit from the starting mode is discharged. The diode 15 and the power supply circuit of the microcircuit are discharged. The device is again ready to monitor the starting mode of the electric motor.

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If the mode of the braked rotor is observed during the operation of the electric motor, the currents in the primary windings of the current transformers 1 and 3 increase and they enter saturation. At the output of a half-wave three-phase rectifier 7, voltage pulses with a frequency of 150 Hz and a constant appear. This component is reduced to zero. The pulses are fed to the input of the inverter 19 of the control unit of the sequence of current pulses. The inverter starts to periodically switch. From the inverter output, the pulses arrive at the first input of the logic element 22 of the detuning unit from the starting mode 9. Since the second input of the logic element 22 is present

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logic level 1 (capacitor 21 is charged), the pulses are unobstructed to the input of the inverter 10 and further to the integrating unit -1 1. When the voltage on the integrating unit 5 reaches a certain value, the threshold amplifying element 12 connects the actuator 13, which turns off the electric motor from the network. Consequently, when a decelerated rotor mode arises during the operation of an electric motor, it is immediately disconnected from the network, which prevents overheating of the windings.

The device is powered by a power source 14. The device is performed on integrated circuits of a CMOS structure, and the executive element 20 is located on a pointer relay. .

Claims (1)

Invention Formula wasp A device for protection of a three-phase asynchronous electric motor against operation on two phases and a braking rotor mode, containing three fast-current current transformers, the primary windings of which are connected to the phase conductors, and the B-star connected in parallel with a burned-out neutral connected to the common bus of the device, and connected to the input of a three-phase half-wave puller, the output of which is connected to the control unit for the sequence of current pulses and the power supply unit. thirty 35 Editor L.Povkhan Order 2664/54 Compiled by L. Anisimova Tehred V. Kadar, Proofreader V. But ha Circulation 618- Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4 with 0 five integrating power unit, executive unit, connected to: with the power supply unit, a detuning unit from the starting mode, made on a capacitor, differing in that. in order to increase reliability and sensitivity, it is additionally equipped with a threshold amplifying unit connected between the integrating unit and the executive body, two diodes, an inverter made on the NAND element and connected between the integrating unit and the detuning unit from the starting mode, made on the element, a resistor connected in series with a capacitor connected to the common bus of the device, and the common connection point of the specified resistor and capacitor is connected to the second input of the I-YE element, first input connected to the output of the pulse sequence control unit vsholnennym on H-NO element, a resistor and zener diode, wherein a resistor included IU SchU yield uni periodkogo rectifier element and to two inputs of AND-block sequence control pulses. The js to which the anode of the Zener diode is also connected, the cathode of which is connected to the common spike of the device, the anode of the first diode is connected to the inputs of the AND-NOT element of the pulse sequence control unit, and the cathode to one of the terminals of the detuning unit resistor, another connected to the adapter in the second diode, the cathode of which is connected to the power supply.