SU1758755A1 - Device for protecting electric motor windings against moisture condensation - Google Patents

Abstract

The invention relates to electrical engineering and can be used to protect the windings of electric motors from moisture condensation. The purpose of the invention is to reduce power consumption in a wide range of changes in temperature and humidity of the environment. Protection is carried out by creating an excess of the temperature of the windings above the ambient temperature and automatically maintaining this excess during the technological pauses by passing an electric current through the windings. In the device, voltage-voltage converters 4 and current-voltage 5 are connected in parallel to windings 1 and thermostable shunt 2 through low-voltage filters b and 7 and limiters 8 and 9. Transmitters 4 and 5 outputs are connected to dividing unit 10, output which is connected to a large-scale amplifier 11, to the second input of which is connected the unit 12 of the temperature coefficient of the material of the windings. The temperature signal of the windings is removed from the output of the large-scale amplifier 11, is fed to the first input of the differential amplifier 13, to the second input of which is connected the sensor 14 of the ambient temperature. The temperature difference signal is fed to the comparison unit 15 with the setpoint 16 that the windings exceed the temperature and then to the control action generation unit 17, which controls the voltage applied to the windings 1 through the actuator 18. 2 Il. VI CL 00 VI SL SL

Description

The invention relates to electrical engineering and can be used to protect against the condensation of moisture windings of electric motors operating with significant intervals between switching on in places with varying humidity and ambient temperature.

The aim of the invention is to reduce power consumption over a wide range of temperature and device variations depending on the humidity of the environment.

FIG. 1 is a block diagram; 2 is a circuit diagram of a device for protecting motor windings from moisture condensation.

The device contains (Fig. 1 and 2) the windings of the electric motor 1 and thermostable

Shunt 2, connected in series by means of the second contacts of switch 3, to which the voltage converters are connected in parallel - voltage 4 and current - voltage 5 through the first and second low-frequency filters 6 and 7 connected in series, and the first and second limiters 8 and 9. The outputs of the converters 4 and 5 are connected to the inputs of the dividing unit 10, the output of which is connected to the first input of the large-scale amplifier 11, to the second input of which the output of the temperature coefficient of the material of the windings 12 is connected, and to the output y - the first input of the differential amplifier 13, to the second input of which is connected the output of the first ambient temperature sensor

14, and at the output the first input of the comparator unit 15, to the second input of which the output of the setpoint device for the winding temperature above the ambient temperature 16 is connected, and the output is connected to the input of the control action shaping unit

17, the output of which is connected to the control input of the actuator 18, through which, through the first contacts of the switch 3, the power source 19 is connected to the series-connected thermostable shunt 2 and windings 1. The input of the first power supply unit 20 is connected to the power source 19. The first output of the first power supply unit 20 is connected to voltage converters - voltage 4 and current - voltage 5, dividing unit 10, control influence forming unit 17, and the second output to scale force body i, unit of temperature coefficient of the material of windings 12, differential amplifier 13, first ambient temperature sensor 14, comparison unit

15, the setpoint for the temperature rise of the windings 16. The first input of the first comparator 12 is connected to the setpoint of the ambient temperature 22, to the second input is the output of the second ambient temperature sensor 23, the output is the input of the first transistor switch 24, the output of which is connected to the input of the relative humidity sensor environment 25, the output of the latter is connected to the first inputs of the second comparator 26, the second input of which is connected to the output of the sensor of relative humidity of the environment 27. The output of the second comparator 26 is connected to the input of the second transistor switch 28. The second power supply unit 29 is connected by its input to the third output of the switch 3, the first output to the first comparator 21. the setpoint temperature

environment 22, the second ambient temperature sensor 23, the first transistor switch 24, the relative humidity controller 25, the second comparator 26, the sensor relative environmental humidity 27, the second output to the second transistor switch 28.

Switch 3 consists of switching device 30, second contacts 31, first contacts 32, switching device 33, third contacts 34, auxiliary contacts 35, Start buttons 36, Stop 37, fourth 38 buttons, fifth 39 and sixth 40 contacts.

The voltage converters — voltage 4 and current — voltage 5 consist of operational amplifiers 41 and 42 with resistors 43 and 44.

The first 6 and second 7 low-pass filters are resistive-capacitance circuits 45, 46, and 47.48.

Sand 8 and second 9 limiters consist of diodes 49, 50 and 51, 52 and resistors 53-56 and 57-60.

The division unit 10 consists of an analog multiplier 61 and an operational amplifier 62 and a resistor 63-68,

The scale amplifier 11 is made on the operational amplifier 69 and the resistors 70,71.

The temperature coefficient of the material of the windings 12 is made in the voltage divider of resistors 72-74. The difference amplifier 13 is made on an operational amplifier 75 with resistors 76-79. The first sensor of ambient temperature 14 is a thermistor 80 connected in the voltage divider circuit of resistors 81-84 and zener diode 85.

Comparison unit 15 is made on the basis of a differential amplifier on the operational amplifier 86 and resistors 87-90.

The over-temperature setting device of the coil 16 is made up of a voltage divider consisting of resistors 91, 92. The control action shaping unit 17 consists of transistors 93, 94 of diode 95, capacitor 96 and resistors 97-104. The parameters of the charging circuit, as well as the magnitude of the voltage supplied to the circuit of the charging capacitor 96, determine the opening angle of the thyristor 18 and, accordingly, the voltage applied to the windings of the electric motor 1. Moreover, the block parameters are selected in such a way that in the absence of a signal The output of dividing unit 10 on thyristor 18 sets the minimum open angle.

The first power supply unit 20 is made of a transformer 105 with two secondary windings that feed rectifier bridges on diodes 106-109 and 110-113. In the filtering and voltage stabilization circuit stand transistor 114, zener diodes 115-117, capacitors 118-123, resistors 124-126.

The first comparator 21 is a dedicated operational amplifier 127 with resistors 128, 129.

The ambient temperature setter 22 is represented by a voltage divider consisting of resistors 130, 131.

The second ambient temperature sensor 23 consists of a voltage divider consisting of resistors 132, 133 and a thermistor with a negative temperature coefficient 134 connected in parallel with resistor 133.

The first transistor switch 24 is represented by an n-p-p type transistor. The ambient relative humidity sender 25 is a voltage divider of resistors 135-137. The second comparator 26 consists of a dedicated opamp 138 with a resistor 139 in the feedback circuit. The ambient relative humidity sensor 27 is a voltage divider of resistors 140, 141 with a moisture sensitive element 142 connected in parallel with resistor 141.

The second transistor switch 28 includes a resistor 143 connected to the base of transistor 144, in the collector circuit of which a relay 145 is connected, shunted by diode 146. The second power supply unit 29 is made of a transformer 147 with two secondary windings feeding rectifying bridges on diodes 148 -151 and 152-155. The filtering and voltage stabilization circuits included capacitors 156-160, resistors 161, 162, and zener diodes 163, 164.

Device to protect the windings of the motor against condensation of moisture (Fig.1 and 2) works as follows.

When the motor is stopped using a button, the switching device 33 is turned off. At the same time, contacts 35 and 40 are closed, contacts 34 in the power supply circuit of switching device 30 and contacts 38 in the power supply circuit of the second power supply unit 29 are closed. Switching device 30 does not receive power because the power supply circuit has an open contact 39 of the relay 145. Second power supply unit 29 provides power to the first 21 and the second 26 comparators, the setting device

temperature 22 and the setpoint relative humidity 25 of the environment, the relative humidity sensor 27 and the second temperature sensor 23 of the environment. the first 24 and the second 28 transistor switches.

It is known that the moistening of the windings of electric motors occurs at a certain ratio of temperature t and relative humidity p of the environment. So moistening of the windings occurs if:

1.1 12 ° C, and p 75%; 2. t 12 ° C, and p 60%.

Therefore, the temperature setting device 22 is selected so that at 120 ° C, at the output of the first comparator 21, a signal appears that opens the transistor switch 24, which, bypassing the resistor 137 in the circuit

setting unit of relative humidity 25. Changes the specified humidity value of 75% to 60%. At t 12 ° C at the output of the first comparator 21, the signal is zero and the relative humidity setting unit 25 sets the humidity 75%.

If t 12 ° C is f 75% or 1 12 ° C p 60% at the output of the second comparator 26, the signal is zero and transistor 144 opens, energizing the relay 145, which closes its contact 39 and zzpiruyut switching device 30. This closes the contacts 31 and 32 that is, the device is put into operation,

By reducing t and y below given

the second comparator 26 switches, transistor 144 closes, de-energizes with relay 145, opens contact 39, which will de-energize the switching device 30 and turn off the device

from work.

Consider the possible cases when operating the device.

When the device is turned on, the temperature of the windings is equal to the ambient temperature

environment. Since in the absence of a signal at the output of the dividing unit, the thyristor 18 transmits a minimum current equal to the sensitivity threshold of the converters 4 and 5, the voltage — the voltage and the current — the voltage, the pulsating voltage drops on the windings 1 and the thermostable shunt 2. Between the windings 1 and shunt 2 and converters 4 and 5, the first and second low-frequency filters 6 are installed.

and 7 separating the DC component from the pulsating voltage, and the first and second amplitude limiters of the signals 8 and 9. At the output of the converter - voltage 4, a signal is proportional to the DC voltage drop on the windings 1, and at the output of the converter, the current - voltage 5 separates a signal proportional to the current of the windings 1. The division unit 10 divides these signals and outputs a signal proportional to the active resistance of the windings 1. Then this signal goes to the large-scale signal the silicon 11, where it is converted into a signal proportional to the temperature of the windings of the electric motor 1} and a voltage proportional to the temperature coefficient of the material of the windings 1 from the temperature coefficient setting 12 is applied to one of the inputs of the large-scale amplifier 11.

Indeed, at the output of the converter the current - voltage 5 separates the signal proportional to the current of the windings 1:

.U§k ,. RI 1

where Us is a constant voltage drop equal to the signal at the output of converter 5;

Ki is the scale factor of converter 5;

RI is the resistance of the thermostable shunt 2.

In this case, the product UsKi is equal to the fall of the constant voltage across shunt 2. Since the windings and shunt 2 are connected in series, this current is common to them. The fall of the constant voltage on the windings 1 is equal to:

Ui 1M-Kg.

where U4 is a DC voltage drop equal to the signal at the output of converter 4;

2 - scale factor of the converter 4,

The division unit 10 divides the voltage IJ4 by the voltage Us:

Ui / K2

Z-K

iRiTRT AZ

 K1 fa

I Ri

Кз - R обм К

where Ks is the scale factor of the division block 10;

K is the total mill scale factor, K KiKaK3 / R2, since RI is also a constant value.

Consequently, a change in the active resistance of the windings 1 is recorded by the division unit 10.

If for the resistance of the windings 1 in the cold state to take its value, reduced to 15 ° C, then the temperature of the hot windings is equal to:

V2 250

R2 -Ris

 - 4-15

0

five

0

five

0

R15

 250 235 R15 2

where R2, R15 are the resistances of the windings in the hot state and at a temperature of 15 ° C.

As can be seen from the formula, to obtain the temperature signal of the windings 1, it is necessary to subtract the signal proportional to the constant coefficient 235 from the output signal of the dividing unit 10. This function is performed by the scale amplifier 11 together with the temperature coefficient setting unit 12,

From the output of the scale amplifier 11, a signal proportional to the temperature of the windings 1 is fed to the first input of the differential amplifier 13, the second input of which receives a signal proportional to the ambient temperature from the sensor 14. Since the temperature of the windings is equal to the ambient temperature, the output of the difference amplifier 13 signal is equal to zero, equal to eul, and the signal at the first input of the comparator unit 15. But at the second input of this block there is a reference voltage setting unit that exceeds the winding temperature

16, which is transmitted to the input of the control action shaping unit 17, opening the thyristor 18. With the passage of current, the windings 1 are heated. The resistance of the windings increases, which leads to an increase in the signal at the output of the scale amplifier 11. At the output of the differential amplifier 13, a signal appears between the temperature of the windings and the environment. Consequently, at the output of the comparison block 15, the signal decreases, the temperature difference is subtracted from the reference voltage 0 signal. The signal is also reduced at the input of the control shaping unit

17, reducing the opening angle of the thyristor

18. As a result, the voltage applied to the windings of the motor 1 decreases, the current and heating intensity of the windings 1 decrease. When the predetermined temperature of the windings 1 reaches above the ambient temperature, the signal from the difference amplifier 13 is fully compensated by the setpoint signal of the temperature rise of the windings 16 and the input of the block of formation of control actions 17 signal is zero. The resistance in the circuit of the charge capacitor 92 during adjustment is chosen in such a way that the opening angle of the thyristor 18 and, accordingly, the current through the thyristor to the windings 1 ensures in the last

five

0

five

heat release equal in quantity to the heat loss of the electric motor to the environment for a given increase in the temperature of the windings above the ambient temperature.

Consider the principle of operation of the device at the time of shutdown of the electric motor. when the temperature of its windings 1 reaches a value significantly higher than a predetermined value exceeding 5-8 ° C. At the same time, the signal at the output of the comparator unit 15 changes its polarity and the control influence forming unit 17 locks the thyristor 18 to a minimum. In the process of cooling the motor, the temperature difference between the windings 1 and the environment decreases. When the temperature exceeds a predetermined value, the thyristor 18 opens and a current flows through the windings of the motor 1, equal to the compensation of heat losses

When the motor starts up at any time by pressing the Start button 36, the switching device 33 is energized, its contact 40 and the auxiliary contact 35 are closed. At the same time, its contacts 34 and 38 are opened, thereby de-energizing the switching device 30 and the second power supply unit 29. In this case, the device is completely turned off.

Thus, the claimed device for protecting motor windings from moisture condensation, as compared to the prototype, allows using it with all electric motors without interfering with their windings, switching the device on and off as needed, which will increase the operational reliability of electric motors, reduce labor costs on maintenance and reduce power consumption.

Claims (1)

The device for protection of motor windings from moisture condensation, containing a switch, the first input of which has terminals for connection to the power supply network, its first output is connected to the power input of the actuating element and the input of the first power supply unit, the second output has terminals for connection to the windings of the electric motor, thermally stable shunt, the output of which through the first low-pass filter connected in series and the transducer is connected to the first input of the current converter - voltage, the output of which connected to the first input of the dividing unit, the voltage converter is a voltage, the first input of which is connected to the terminals for connecting the windings of the electric motor through the serially connected second limiter and low-pass filter, the second input of the voltage converter is connected to the second inputs of the current converter - voltage, dividing unit, the first output of the first power supply unit and the first input of the control shaping unit, the output of the voltage-voltage converter is connected to the friction The input of the division unit, the output of which is connected to the first input of the scale amplifier, the output of the latter is connected to the first input of the differential amplifier, the input of the first ambient temperature sensor is connected to the second input of the first power supply unit, the second input of the differential amplifier, the first input of the comparison unit, the input of the setter over temperature 0 windings above the ambient temperature and the second input of the large-scale amplifier, the third input of which is connected to the input of the first sensor through the unit of temperature coefficient of the winding material 5 of the ambient temperature, the output of which is connected to the third input of the differential amplifier, the output of which is connected to the second input of the comparator unit, the third input of which is connected to the output of the setpoint that the windings exceed the ambient temperature, the output of the comparator unit is connected to the second input of the control unit impacts which output through 5 serially connected actuator and thermostable shunt is connected to the second input of the switch, the second output of the first low-frequency filter is connected to the second input of the second 0 low-pass filter, characterized by that, in order to reduce energy consumption in a wide range of changes in ambient temperature and humidity, a first comparator was additionally introduced in it, the first input of which is connected to the output of the newly introduced ambient temperature setpoint, the second input is connected to the output of the newly introduced second temperature sensor environment, and the third input is connected to the inputs of the setter of the ambient temperature, the second sensor of the ambient temperature, the first inputs of the newly introduced first transistor 5 key, setter for relative humidity of the environment, second comparator, sensor for relative humidity of the environment and with the first output of the newly introduced second power supply unit, the output of the first comparator is connected to the second the input of the first transistor switch, the output of which is connected to the second input of the setpoint relative environmental humidity, the output of which is connected to the second input of the second comparator, to the third input of which the output of the sensor of relative humidity of the environment is connected, the second transistor switch, the first input of which is connected to the output of the second comparator, the second input is connected to the second output of the second power supply unit, and the output is connected to the third input of the switch, to the third output of which the input of the second power supply unit pi is connected tani. W.1 2