Bearing temperature monitoring device for electric motor

Abstract

The application relates to a bearing temperature monitoring device of a motor, which comprises a comparator A3, the inverting phase input end of the comparator A3 is connected with a voltage signal U2 corresponding to the bearing temperature, and the non-inverting phase input end of the comparator A3 is connected with a set voltage U1 continuously rising with time, wherein when the slope of the voltage signal U2 is greater than the slope of the set voltage U1, the output end of the comparator A2 outputs an alarm signal. The beneficial effects are as follows: 1. the change rate of the set voltage is the safe change rate of the bearing temperature, the change rate of the bearing temperature corresponds to the bearing fault degree, the greater the fault degree, the greater the change rate, when the change rate of the bearing temperature is greater than the safe change rate, the monitoring device outputs the alarm signal, the user is reminded to arrange time for the motor maintenance, and sudden stop production is avoided; the conventional set voltage is a fixed value, and the change rate of the bearing temperature cannot be monitored; 2. the influence of the environment temperature can be eliminated, and the alarm is accurate; 3. the bearing temperature change rate monitoring circuit has simple structure, reliable work and low manufacturing cost.

Description

Technical Field

[0001] This invention relates to a bearing temperature monitoring device for an electric motor. Background Technology

[0002] If the bearing is worn or poorly lubricated, it will generate heat, which will damage the motor if not dealt with in time.

[0003] The usual method for monitoring bearing overheating is to manually measure the temperature of the bearing area with a thermometer. However, this method has the drawback of not being able to detect faults in a timely manner. Some systems employ online monitoring, where the temperature monitor outputs an alarm or cuts off the power when the bearing temperature reaches a set value, prompting the user to stop the machine for maintenance. However, this method has limitations. It cannot determine the bearing's failure trend. For example, if the bearing temperature is 90°C but its temperature curve flattens over a period of time, it indicates the bearing can continue operating. If the set value is also 90°C, then stopping the machine for maintenance based on the monitor's alarm is unnecessary. Furthermore, in summer, higher ambient temperatures can cause misjudgments. Also, if the bearing temperature rises from 75°C to 85°C over a period of time (e.g., continuous operation for 8 hours), this indicates a developing bearing failure, but the detector will not alarm. Summary of the Invention

[0004] To address the above shortcomings, this invention proposes a bearing temperature monitoring device for electric motors, which can predict faults based on changes in bearing temperature, giving users the opportunity to arrange maintenance and avoid production stoppages caused by sudden failures.

[0005] The technical solution of the present invention is a bearing temperature monitoring device for an electric motor, which includes a comparator A3. The inverting input terminal of the comparator A3 is connected to a voltage signal U2 corresponding to the bearing temperature. The device is characterized in that the non-inverting input terminal of the comparator A3 is connected to a set voltage U1 that continuously increases over time, and the output terminal of the comparator A2 outputs an alarm signal.

[0006] Its beneficial effects are: 1. The set voltage output by the set voltage generator of this monitoring device gradually increases over time. The rate of change of the set voltage is the safe rate of change of the bearing temperature. The rate of change of the bearing temperature corresponds to the degree of bearing failure. The greater the degree of failure, the greater the rate of change. When the rate of change of the bearing temperature is greater than the safe rate of change, the monitoring device outputs an alarm signal to remind the user to schedule time to maintain the motor and avoid sudden production stoppage. Conventional set voltage is a fixed value and cannot monitor the rate of change of the bearing temperature. 2. It can eliminate the influence of ambient temperature and the alarm is accurate. 3. The bearing temperature change rate monitoring circuit has a simple structure, reliable operation, and low manufacturing cost. Attached Figure Description

[0007] Figure 1 This is the circuit schematic diagram of the present invention.

[0008] Figure 2 Another circuit schematic for setting the voltage generator.

[0009] Figure 3 for Figure 1 Voltage waveforms at relevant points. Detailed Implementation

[0010] A bearing temperature monitoring device for an electric motor includes a comparator A3, the inverting input terminal of the comparator A3 is connected to a voltage signal U2 corresponding to the bearing temperature, characterized in that the non-inverting input terminal of the comparator A3 is connected to a set voltage U1 that continuously increases over time, and the output terminal of the comparator A2 outputs an alarm signal.

[0011] The set voltage is generated by a set voltage generator, which includes an operational amplifier A2. The non-inverting input of operational amplifier A2 is grounded through capacitor C3. The inverting input of operational amplifier A2 is connected to its output. The output of operational amplifier A2 is connected to one end of resistor R7. The other end of resistor R7 is connected to power supply VDD through resistor R6. The other end of resistor R7 is connected to the non-inverting input of operational amplifier A2 through resistor R5. The non-inverting input of operational amplifier A2 is connected to the output of electronic switch G1. The input of electronic switch G1 is connected to voltage signal U2 through resistor R4. The control electrode of electronic switch G1 is connected to the output of comparator A1. The non-inverting input of comparator A1 is connected to power supply VDD through resistor R2. The non-inverting input of comparator A1 is grounded through resistor R3. The inverting input of comparator A1 is connected to voltage signal U2 through resistor R4. The resistance of resistor R4 is much smaller than that of resistor R5.

[0012] The circuit principle is as follows: the power supply VDD charges the capacitor C3 at a constant current through resistors R5 and R6. The voltage of capacitor C3 rises linearly, and the voltage at the output terminal of operational amplifier A2 also rises accordingly. The output voltage of operational amplifier A2 is the set voltage U1. The resistance value of resistor R5 is much larger than the resistance values ​​of resistors R6 and R7. The duration for which the set voltage U1 continues to rise can be achieved by selecting the resistance value of resistor R5 and the capacitance of capacitor C3. Resistor R5 can be a variable resistor, and adjusting resistor R5 can also change the slope of the set voltage U1. Considering that the bearing temperature rises from room temperature to a stable temperature during the initial operation, and the rate of change of bearing temperature during this period is much greater than the rate of change during the stable temperature period, in order to prevent misjudgment, electronic switch G1 is turned on during this period, and capacitor C3 is charged by voltage signal U2 through resistor R4. When the bearing temperature reaches the stable temperature (e.g., 75°C), comparator A1 changes from high level to low level, electronic switch G1 is turned off, and capacitor C3 is charged by power supply VDD through resistors R5 and R6; the set value of the stable temperature is determined by resistors R2 and R3.

[0013] The rate of change of the set voltage U1 can be set by resistor R5. The range of the rate of change of the set voltage U1 is from 1°C / hour to 2°C / hour, preferably 1.5°C / hour.

[0014] Based on the characteristics of an 8-hour workday, the charging time for capacitor C3 is greater than or equal to 8 hours.

[0015] The set voltage generator can also have the following structure: a transistor T2, the base of which is connected to the slider of potentiometer W3; one end of potentiometer W3 is connected to power supply VDD through resistor R10, and the other end is grounded through resistor R11; the emitter of transistor T2 is connected to power supply VDD through resistor R12; the collector of transistor T2 is grounded through capacitor C5; the collector of transistor T2 is connected to the output of electronic switch G1'; the input of electronic switch G1' is connected to voltage signal U2 through resistor R4'; the control terminal of electronic switch G1' is connected to the output of comparator A1'; the non-inverting input of comparator A1' is connected to power supply VDD through resistor R2'; the non-inverting input of comparator A1' is grounded through resistor R3'; and the inverting input of comparator A1' is connected to voltage signal U2. The collector of transistor T2 outputs the set voltage U1. The resistance of resistor R4' is much smaller than that of resistor R12.

[0016] The above circuit constitutes a constant current source capacitor charging circuit. The voltage of capacitor C5 is proportional to the charging time. Adjusting potentiometer W3 or resistor R12 can change the charging speed, i.e., the slope of the set voltage U1.

[0017] The output of comparator A3 is connected to the base of transistor T1 through resistor R9. The emitter of transistor T1 is connected to power supply VDD. The collector of transistor T1 is grounded through the coil J1 of relay. A diode D2 is connected in parallel with the coil J1 of relay. The anode of diode D2 is grounded. The contacts of the relay can control the alarm or control the motor power supply.

[0018] To prevent the voltage signal U2 from being equal to the set voltage U1 during the initial operation of the bearing, the inverting input of comparator A3 is connected to the cathode of diode D1. The anode of diode D1 is connected to the voltage signal U2. Thus, due to the voltage drop across diode D1, the voltage signal U2 will be less than the set voltage U1.

[0019] To prevent interference from noise in the voltage signal U2, the inverting input of comparator A3 is grounded through capacitor C4, and resistor R8 is connected between the voltage signal U2 and diode D1.

[0020] The variation pattern of the set voltage U1 can be derived from the test data of bearing operating temperature changes; bearing failures (such as wear, lubricant aging, pitting) develop gradually, and the temperature will also rise slowly and regularly, as shown in the following... Figure 3 As shown in curve 1; Voltage signal U2 such as Figure 3 As shown in curve 2, the slope of curve 2 varies depending on the degree of bearing failure. When the failure is minor, the slope of curve 2 is less than that of curve 1, and the two will not intersect. When the bearing failure is severe, the slope of curve 2 will be greater than that of curve 1, and the two will intersect at a certain moment t1. When they intersect, U2 is greater than or equal to U1, and comparator A3 outputs an alarm signal. When the slope of curve 2 is less than that of curve 1, the two will not intersect, and the bearing failure can be considered minor. Comparator A2 will not output an alarm signal.

[0021] Figure 3 The steeper portion of curve 1 corresponds to the change in bearing temperature as it rises from room temperature to a stable temperature.

[0022] It should be noted that the standard setting voltage is a fixed value, assuming it corresponds to a bearing temperature of 90°C. Figure 3 As shown by line 3, the intersection of curve 2 and line 3 occurs at time t1'; while the intersection of curve 2 and curve 1 occurs at time t1. This indicates that monitoring the bearing's temperature change rate can detect bearing failures in advance. Furthermore, monitoring the bearing's temperature change rate can eliminate the influence of ambient temperature.

[0023] The usage method is as follows: when the user leaves work, turn off the power supply VDD and when the user arrives at work, turn on the power supply VDD.

Claims

1. A bearing temperature monitoring device for an electric motor, comprising a comparator A3, wherein the inverting input terminal of the comparator A3 is connected to a voltage signal U2 corresponding to the bearing temperature, characterized in that, A set voltage U1 that rises continuously over time is connected to the non-inverting input of comparator A3, and an alarm signal is output from the output of comparator A2.

2. The bearing temperature monitoring device for an electric motor according to claim 1, characterized in that, The set voltage continues to rise for more than 8 hours.

3. The bearing temperature monitoring device for an electric motor according to claim 1, characterized in that, The set voltage is generated by a set voltage generator, which includes an operational amplifier A2. The non-inverting input of operational amplifier A2 is grounded through capacitor C3. The inverting input of operational amplifier A2 is connected to its output. The output of operational amplifier A2 is connected to one end of resistor R7. The other end of resistor R7 is connected to power supply VDD through resistor R6. The other end of resistor R7 is connected to the non-inverting input of operational amplifier A2 through resistor R5. The non-inverting input of operational amplifier A2 is connected to the output of electronic switch G1. The input of electronic switch G1 is connected to voltage signal U2 through resistor R4. The control electrode of electronic switch G1 is connected to the output of comparator A1. The non-inverting input of comparator A1 is connected to power supply VDD through resistor R2. The non-inverting input of comparator A1 is grounded through resistor R3. The inverting input of comparator A1 is connected to voltage signal U2.

4. The bearing temperature monitoring device for an electric motor according to claim 1, characterized in that, The voltage generator includes a transistor T2. The base of transistor T2 is connected to the slider of potentiometer W3. One end of potentiometer W3 is connected to power supply VDD through resistor R10, and the other end of potentiometer W3 is grounded through resistor R11. The emitter of transistor T2 is connected to power supply VDD through resistor R12, and the collector of transistor T2 is grounded through capacitor C5. The collector of transistor T2 is connected to the output terminal of electronic switch G1'. The input terminal of electronic switch G1' is connected to voltage signal U2 through resistor R4'. The control terminal of electronic switch G1' is connected to the output terminal of comparator A1'. The non-inverting input terminal of comparator A1' is connected to power supply VDD through resistor R2', and the non-inverting input terminal of comparator A1' is grounded through resistor R3'. The inverting input terminal of comparator A1' is connected to voltage signal U2.

5. The bearing temperature monitoring device for an electric motor according to claim 1, characterized in that, The rate of change of voltage U1 is set to 1.5°C / hour.

6. The bearing temperature monitoring device for an electric motor according to claim 3 or 4, characterized in that, The output of comparator A3 is connected to the base of transistor T1 through resistor R9. The emitter of transistor T1 is connected to power supply VDD. The collector of transistor T1 is grounded through the coil J1 of relay. A diode D2 is connected in parallel with the coil J1 of relay. The anode of diode D2 is grounded. The contacts of the relay control the alarm or control the motor power supply.

7. The bearing temperature monitoring device for an electric motor according to claim 1, characterized in that, The inverting input of comparator A3 is connected to the cathode of diode D1. The anode of diode D1 is connected to the voltage signal U2.

8. The bearing temperature monitoring device for an electric motor according to claim 7, characterized in that, The inverting input of comparator A3 is grounded through capacitor C4, and resistor R8 is connected between voltage signal U2 and diode D1.

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