Device for protection of electric motor from non full phase modes and overload

FIELD: electric engineering, possible use for protecting three-phased asynchronous electric engines from non full phase modes and overloads.

SUBSTANCE: device contains asymmetry indicator for voltages of powering network, first, second and third threshold blocks, signals delay block, supporting voltage block, executing block, first and second current transformers, current sensor for asymmetry of phase currents of electric motor, while for excluding galvanic connection of device and electric network, introduced additionally are: diode optic couple into sensor of asymmetry of feeding network voltages, and into support voltage block - separating transformer. To detect reason of disabling of electric motor introduced additionally is fourth threshold block, which depending on abnormal mode of operation of network or electric motor sends positive impulse to light diodes, indicating reason of disabling of electric motor.

EFFECT: increased reliability and expanded functional capabilities.

2 dwg

 

The invention relates to electrical engineering and can be used to protect three-phase induction motors on unbalanced modes and overload.

Known devices for protecting three-phase asynchronous motors from loss of phase, phase containing the sensors, the threshold elements, the output relay, RC filters, controls, filters current reverse sequence and the amplifier /see A.S. 1580479, CL N 02 N 7/08, 1990, A.S. 2126037, N 02 N 3/26, 1999/.

The disadvantage of such devices is the lack of galvanic isolation device supplying the motor network, which reduces reliability. Also the disadvantages are the lack of control voltage unbalance, therefore it is impossible to determine, for any reason, disconnect the motor from phase failure or short-circuit the windings of the motor, which is a low functionality of the device.

It is also known a device selected as a prototype of the proposed technical solution described in A.S. N1584028, CL N 02 N 7/08, 1990, to control and protect the motor from unbalanced modes and winding short circuits containing transformers, control units unbalance of currents and voltages in the sensor block of the reference voltage, the first and second threshold blocks.

The disadvantage of this device are the two which is necessary to combine the zero point of the windings of the motor, connected in star, with the zero point of the device, which reduces the reliability of the device, when disturbances in the network, for example when switching surges, as well as when the resistance of the grounding device, will change the current and voltage zero-sequence that will result in incorrect operation of the device.

The technical result is increased reliability and enhanced functionality.

The technical result is achieved in that in the device to protect the motor from unbalanced modes and overload containing the sensor unbalance voltage supply network, the inputs of which are terminals for connection to respective phases of the supply network, the first, second and third threshold units, a unit delay signals, the block of the reference voltage, the Executive unit, the first and second current transformers in the supply circuit of the motor, the current sensor unbalance currents of phases of the motor, it is additionally an optocoupler in the scheme of the sensor unbalance voltage of the mains, the fourth threshold unit, the first input connected to the first input of the third threshold block and the output of the sensor unbalance voltage of the mains, and the third input is connected to the first input of the second threshold unit and the second output of the delay block signal, the first input connected the output of the current sensor unbalance currents of phases of the motor, connected to the first and second current transformers, the secondary winding of the second transformer is connected to a second input of the unit delay signal and the first output of the unit delay signal is connected to the first input of the first threshold unit, the outputs of the first, second and third threshold blocks are interconnected and connected to the first input of the Executive unit, the second and third inputs of which are connected with the first and second input reference voltage and connected to the phase voltage, and the fourth input of the control unit connected to the first output of the reference voltage, while the second inputs of the first, second, third and the fourth threshold blocks are interconnected and connected to the second output of the reference voltage.

Introduction the fourth threshold block allows you to determine the cause of the disconnection of the motor from the network claimed device light indication LEDs. The sensor current unbalance currents of phases of the motor and the sensor voltage unbalance phase, reacting to changes in currents and voltages in the reverse order, respectively, and an introduction to sensor voltage unbalance phase diode of the optocoupler and the separation of the transformer in the unit of the reference voltage, allows to apply the scheme, galvanically nesv is connected to an external mains supply, what improves the reliability of the claimed device. For normal functioning of the device do not need to connect the zero point of the windings of the stator of the motor with earthing device, which is necessary for the normal functioning of the prototype, resulting in reduced reliability of the known device.

Figure 1 shows a block diagram of the device, figure 2 shows a schematic diagram of a device.

The device includes transformers 1, 2 DC in the circuit of the motor 3, the secondary winding of which is connected to the sensor 4 of unbalance currents of phases of the motor, the output of which is connected to the unit 5 delays the signal, to which is also connected to the secondary winding of the transformer 2 current. The first output unit 5 delays the signal connected to the first input of the threshold unit 6, and a second output connected to the first input of the threshold unit 7 and the third input of the threshold unit 8, the first input connected to the first input of the threshold unit 9 and is connected to the output of the sensor 10 of the unbalance voltage of the mains supply, which is connected to the phase wire of the mains. The outputs of threshold units 6, 7, 9 are interconnected and connected to the first input of the control unit 11, the second and third input connected to the first and the second input unit 12 of the reference voltage and connected to the phases of the WMD supply voltage. The first output unit 12 of the reference voltage is connected to the fourth input of the control unit 11, and a second output connected to second inputs of threshold units 6, 7, 8 and 9.

Sensor 4 current unbalance currents of the phases contains RC-shift linkage, made on the resistors 13, 14, 15 and the capacitor 16. The resistance of the resistors and the capacitor are selected so that in the normal mode, the shift vectors of the voltage drops at the resistors 14, 15 was 180 electrical degrees, and the lengths of these vectors stresses were equal.

Unit 5 delays the signal consists of two RC-circuits that contain resistors 17, 18, 19, 20, 21, 22, the capacitors 23, 24 and the diodes 25, 26. This unit eliminates the possibility of triggering threshold blocks 6, 7 and the control unit 11 when starting the motor 3.

Threshold blocks 6, 7, 9 made in the form of RS-flip-flops 27, 28, 29, and R inputs is supplied reference voltage, and T the outputs of each trigger device is activated the LEDs 30, 31, 32 and connected to the diodes 33, 34, 35, respectively.

The threshold unit 8 is designed as two RS-flip-flops 36, 37, T-outputs which device is activated the LEDs 38, 39, and R inputs is supplied reference voltage. S-input of the trigger 36 is connected to the E input of the trigger 37 is first input of the threshold unit 8, and S-input of the trigger 37 is connected to the E input of the trigger 36 and is tritlington threshold unit 8. This unit provides an opportunity to determine what kind of protection has switched off the motor 3, the protection voltage unbalance (led lights up 38) or protection against unbalance currents (led lights up 39).

The sensor 10 of the unbalance voltage of the mains supply contains RC-shift linkage, made on the resistors 40, 41 and capacitors 42, 43, midpoints, which is connected to a diode bridge 44, the output of which through the Zener diode 45, resistors 46, 47 and capacitor 48 is connected to the photodiode of the optocoupler 49, which is connected to the output of the sensor 10 of the unbalance voltage of the mains supply.

Executive unit 11 includes two transistor switch, is performed on the transistors 50, 51 and resistors 52, 53, 54. The relationship between the thyristor transistor 55 and the key is made on the opto-coupler 56, the input of which is connected to the collector of transistor 51, and the output adjusting device is activated contacts 57. If this is consistently the optocoupler included resistor 58, and between the anode and control electrode of the thyristor 55 included resistance 59. Executive unit 11 includes a button 60, "Stop", which is connected to the button 61 "start"device is activated block contacts 62, which is connected to including the coil 63, which is connected to the zero conductor.

The block 12 of the reference voltage power supply includes an isolation transformer 64, the primary winding to the th is connected to the mains, and secondary to the diode bridge 65, which is loaded by the Zener diode 66, a smoothing capacitor 67 and signal the presence of voltage photodiode 68, enabled through a resistor 69. Also in the circuit of the reference voltage switched capacitor 70 and resistor 71 to reset the E-logon trigger 27.

The enabling and disabling of the electric motor 3 from the mains circuit breaker contactor 72 and 73, which includes a coil which is a coil 63.

The device operates in two modes "Work" and "setting". In the "run" mode the device operates as follows.

In the initial position, the key 57 is open, the button 60 "Stop" is closed. When you enable the automatic switch 72 voltage appears at the output of block 12 reference voltage. The first time charging the capacitor 70 than the reset voltage value on the T-outputs of all flip-flops 27, 28, 29. When the allowable unbalance voltage network voltage at the output of the sensor 10 of the unbalance voltage of the mains supply is not enough to activate the trigger 29 and 36, and the current in the circuit to contactor 73 to the motor 3 is absent, and the voltage on the S-inputs of flip 27, 28 missing. Therefore, all triggers are closed, respectively, is closed, the transistor 50 and transistor 51 is open. The current flows through the diode of the optocoupler 56, whereupon the optocoupler is opened and will occupait signal to open gate 55. When the button 61 "start" coil 63 tightens power contacts of the contactor 73 and the auxiliary contact 62. The motor 3 is energized.

When the unbalance current is the sum of the voltage drops at the resistors 14, 15 is different from zero and the output of the sensor 4 current unbalance currents of the phases appears a voltage which is rectified by diode 25 and energizes the first RC circuit block 5 signal delay. Further unbalance the capacitor is charging and forming a positive pulse to the S input of the trigger 28 and 37 and the input of the trigger 36, which prevents the trigger 36 to be opened even when a positive pulse to the S input, which appears when the voltage unbalance. When opening triggers 28 and 37 light up the LEDs 31, 39, and the led 38 is illuminated to indicate that the asymmetry of the phase currents. Then you receive a positive pulse to the base of transistor 50, it opens, and the transistor 51 is closed, the current in the circuit of the collector of the transistor 51 stops flowing and closes the optical coupler 56. As a result, the thyristor 55 is closed and de-energized coil 63, the contactor 73 is turned off and the motor 3 is turned off.

When an overcurrent charging the second RC circuit unit 5 delays the signal, if the current phase is not reduced, and the voltage on the S-input of the trigger 27 quarter exceeds the limit is of the trigger 27, it is opened. You receive a positive signal on the photodiode 30 that indicates congestion, and works Executive unit 11, de-energized coil 63, the contactor 73 is turned off and the motor 3 is turned off.

When the unbalance voltage is the sum of the voltage drops across the resistor 40 and the capacitor 43 is different from zero. At the output of the diode bridge 44 receive the voltage charging the capacitor 48 and, if the voltage asymmetry does not stop, then opens the optocoupler 49 and generates a positive pulse on the S-input of the trigger 29 and 36 and the E-logon trigger 37, which prevents the trigger 37 to be opened even when a positive pulse to the S input, which appears when the unbalance currents. When reaching a certain value of the voltage on the S-input of the trigger 29 and 36 are opened, resulting in led lights 32, 38, and led 39 does not light up to indicate that the voltage unbalance. Then actuates the actuating unit 11, de-energized coil 63, the contactor 73 is turned off and the motor 3 is turned off.

In "setup" mode the device operates as follows. The key 57 is closed. Automatically switch 72, pressed 61 "start"as the key 57 bypasses the optocoupler 56, the thyristor 55 will be opened regardless of the voltage at the input of the control unit 11. So the WMD motor 3 can be disabled only by pressing the button 60, "Stop." Thus, the action triggers can be judged only by the lighting of the photodiodes. In "setup" mode is used for setting the values of the resistances of resistor 47 to offset unbalance voltage, resistor 17 to offset unbalance currents, resistor 20 for offset against current overloads.

Thus, this device can be used to protect the motor from overload, unbalance voltage and current phases. The use of separation schemes trigger allows you to identify each reason. This function is useful because it allows rapid restoration of the technological process involving the motor, by addressing specific problems.

Device to protect the motor from unbalanced modes and overload containing the sensor unbalance voltage supply network, the inputs of which are terminals for connection to respective phases of the supply network, the first, second and third threshold units, a unit delay signals, the block of the reference voltage, the Executive unit, the first and second current transformers in the supply circuit of the motor, the current sensor unbalance currents of phases of the motor, characterized in that it additionally an optocoupler in the scheme of the sensor unbalance voltage supply network, Thursday is rty threshold block, first input connected to the first input of the third threshold unit and the sensor output of the unbalance voltage of the mains, and the third input is connected to the first input of the second threshold unit and the second output of the delay block signal, the first input connected to the output of the sensor current unbalance currents of phases of the motor, is connected to the first and second current transformers, the secondary winding of the second transformer is connected to the second input of the unit delay signal and the first output of the unit delay signal is connected to the first input of the first threshold unit, the outputs of the first, second and third threshold blocks are interconnected and connected to the first the input of the control unit, the second and third inputs of which are connected with the first and second input reference voltage and connected to the phase voltage, and the fourth input of the control unit connected to the first output of the reference voltage, while the second inputs of the first, second, third and fourth threshold blocks are interconnected and connected to the second output of the reference voltage.



 

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