Motor overheating protection circuit
By designing a motor overheating protection circuit, using transistors and thermistors to detect the motor temperature, controlling the motor shutdown and sending an alarm, it solves the problem of difficulty in stopping timely when the motor is overheated, and effectively protects the motor.
Patent Information
- Application Number
- CN202421556578.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-03
- Publication Date
- 2025-08-12
- Estimated Expiration
- 2034-07-03
AI Technical Summary
In the prior art, it is difficult to stop running in time when the motor is overheated, resulting in damage and lack of an effective protection mechanism.
A motor overheating protection circuit is designed, which induces the motor temperature through the control circuit, uses transistors and thermistors to detect the overheating situation, controls the relay circuit to shut down the motor, and issues an alarm through the alarm circuit.
It realizes timely shutdown when the motor is overheated, protects the motor, avoids damage, and displays overheating status through the light emitting diode, providing visual alarms.
Smart Images
Figure CN223218827U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a motor overheat protection circuit in the technical field of motor overheat protection. Background Art
[0002] Motor overheating is a common problem, usually caused by the following reasons: 1. Excessive load. When the load carried by the motor exceeds its rated load, it consumes more energy and generates additional heat, leading to overheating; 2. Poor ventilation. The motor requires good ventilation to dissipate heat. If the environment around the motor is closed or the ventilation holes are blocked, the heat dissipation effect will be affected, resulting in overheating; 3. Internal faults in the motor, such as coil short circuits and rotor damage, will cause unstable motor operation and generate a lot of heat. Generally, methods such as improving ventilation conditions and regular maintenance and protection can be used to prevent overheating. However, in actual operation, the motor may also overheat due to some sudden and unexpected situations. If it is not stopped in time, it will be damaged due to overheating. Utility Model Content
[0003] The purpose of the utility model is to provide a motor overheat protection circuit, which can stop the motor from running in time when the motor is overheated, thereby protecting the motor.
[0004] To achieve the above object, the utility model provides a motor overheat protection circuit, which includes a control circuit, and the control circuit is connected to an alarm circuit and a relay circuit respectively.
[0005] Compared with the prior art, the beneficial effect of the present invention is that the temperature of the motor is sensed by the control circuit, thereby issuing a control instruction to the relay circuit, and the relay circuit controls the on and off of the motor according to the control instruction. In this process, once overheating occurs, the alarm circuit will sound an alarm and the motor will stop running, thereby achieving the purpose of protecting the motor.
[0006] As a further improvement of the present utility model, the control circuit includes a transistor V1, the base of the transistor V1 is respectively connected to one end of the varistor RP and one end of the thermistor RT1, the other end of the varistor RP is connected to the alarm circuit, the other end of the thermistor RT1 is connected to one end of the thermistor RT2, the other end of the thermistor RT2 is connected to one end of the thermistor RT3, the other end of the thermistor RT3 is connected to one end of the resistor R3, and the other end of the resistor R3 is respectively connected to the emitter of the transistor V1 and the emitter of the diode V2; the collector of the transistor V1 is respectively connected to the alarm circuit and one end of the resistor R4, the other end of the resistor R4 is respectively connected to one end of the resistor R5 and the base of the transistor V2, the other end of the resistor R5 is connected to one end of the resistor R3 and is connected to the negative electrode of the power supply, and the collector of the transistor V2 is connected to the relay circuit.
[0007] Under normal circumstances, the thermistors are at room temperature and their total resistance is low. At this time, transistor V1 is off and V2 is on, which activates the relay circuit and allows the motor to operate on mains power. If the motor overheats locally due to a fault or other reason, as long as one thermistor is heated, its resistance will increase, causing transistor V1 to conduct and V2 to cut off. The relay circuit then powers the motor off and stops operation, achieving the desired protection.
[0008] As a further improvement of the present utility model, the alarm circuit includes a light-emitting diode VD1, the cathode of the light-emitting diode VD1 is connected to the negative electrode of the power supply, the positive electrode of the light-emitting diode VD1 is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the other end of the rheostat RP, the other end of the rheostat is also connected to one end of the resistor R2, the other end of the resistor R2 is connected to the positive electrode of the light-emitting diode VD2, and the negative electrode of the light-emitting diode VD2 is respectively connected to the collector of the transistor V1 and one end of the resistor R4.
[0009] In this way, when the transistor V1 is cut off and V2 is turned on, the light-emitting diode VD1 emits green light, while the light-emitting diode VD2 does not emit light, indicating that the motor is in normal operation; on the contrary, when the transistor V1 is turned on and V2 is cut off, the light-emitting diode VD1 does not emit light, while the light-emitting diode VD2 emits red light, indicating that the motor is in an overheated state.
[0010] As a further improvement of the present invention, the relay circuit includes a relay K, one end of the coil of the relay K is respectively connected to the collector of the transistor V2 and the positive electrode of the freewheeling diode VD3, and the other end of the coil of the relay K is respectively connected to the positive electrode of the power supply and the negative electrode of the freewheeling diode VD3.
[0011] In this way, when the transistor V1 is cut off and V2 is turned on, the coil of relay K is energized and attracted, so that the motor is powered and operates; when the transistor V1 is turned on and V2 is cut off, the coil of relay K loses power, so that the motor stops and serves the purpose of overheat protection. The freewheeling diode can protect the transistor from being broken down by the back electromotive force of the inductor when the relay coil loses power.
[0012] As a further improvement of the present invention, the thermistors RT1 , RT2 and RT3 have consistent characteristics and are evenly distributed in the stator winding of the motor.
[0013] In this way, the local heating of the motor can be better detected, and the thermistors are equivalent to a whole after being connected in series, so the circuit detection accuracy is higher and the response is more sensitive and accurate.
[0014] As a further improvement of the present invention, the Curie temperatures of thermistors RT1, RT2 and RT3 are 40° C. lower than the insulation temperature of the motor.
[0015] In this way, the resistance limit temperature of the thermistor is 40°C lower than the limit temperature of the motor insulation, which can effectively ensure that the insulation material of the motor will not be damaged due to excessive temperature. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 This is the circuit diagram of the utility model. DETAILED DESCRIPTION
[0017] The present invention is further described below with reference to the accompanying drawings:
[0018] like Figure 1 A motor overheat protection circuit shown includes a control circuit, which is connected to an alarm circuit and a relay circuit respectively.
[0019] The control circuit includes a transistor V1, the base of which is connected to one end of a variable resistor RP and one end of a thermistor RT1, respectively; the other end of the variable resistor RP is connected to an alarm circuit; the other end of the thermistor RT1 is connected to one end of a thermistor RT2; the other end of the thermistor RT2 is connected to one end of a thermistor RT3; the other end of the thermistor RT3 is connected to one end of a resistor R3; the other end of the resistor R3 is connected to the emitter of the transistor V1 and the emitter of the diode V2, respectively; the collector of the transistor V1 is connected to the alarm circuit and one end of a resistor R4, respectively; the other end of the resistor R4 is connected to one end of a resistor R5 and the base of the transistor V2, respectively; the other end of the resistor R5 is connected to one end of the resistor R3 and to the negative electrode of the power supply; and the collector of the transistor V2 is connected to the relay circuit.
[0020] The alarm circuit includes a light-emitting diode VD1, the cathode of the light-emitting diode VD1 is connected to the negative electrode of the power supply, the anode of the light-emitting diode VD1 is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the other end of the variable resistor RP, the other end of the variable resistor is also connected to one end of the resistor R2, the other end of the resistor R2 is connected to the anode of the light-emitting diode VD2, and the cathode of the light-emitting diode VD2 is respectively connected to the collector of the transistor V1 and one end of the resistor R4.
[0021] The relay circuit includes a relay K. One end of the coil of the relay K is connected to the collector of the transistor V2 and the positive electrode of the freewheeling diode VD3 respectively, and the other end of the coil of the relay K is connected to the positive electrode of the power supply and the negative electrode of the freewheeling diode VD3 respectively.
[0022] Thermistors RT1, RT2, and RT3 have the same characteristics and are evenly distributed in the stator winding of the motor. The Curie temperatures of thermistors RT1, RT2, and RT3 are 40°C lower than the insulation temperature of the motor.
[0023] In this utility model, the selection of PTC thermistors depends on the motor's insulation class. The Curie temperature of the PTC thermistor is selected to be approximately 40°C lower than the corresponding maximum temperature limit for the motor's insulation class. For example, for Class E insulation, which has a maximum allowable operating temperature of 120°C and is commonly used in medium and small motors, a PTC thermistor with a Curie temperature of 80°C is selected. RT1, RT2, and RT3 are three step-type PTC thermistors with identical characteristics, evenly distributed throughout the motor's stator windings. The number of thermistors can be adjusted based on actual conditions and is not limited to three.
[0024] Under normal circumstances, PTC thermistors are at room temperature, their resistance is very low, and the total resistance when connected in series is also low. At this time, V1 is off, V2 is on, the coil of relay K is energized, and the normally open contacts close, allowing the motor to operate on mains power. If the motor overheats locally due to a fault, as long as one PTC thermistor is heated above the preset temperature, its resistance will increase, increasing the total resistance of the entire series of thermistors. Consequently, V1 is turned on, V2 is turned off, VD2 displays a red alarm, the de-energized coil of relay K is released, and the motor stops, achieving its protective function.
[0025] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed herein, technicians in this field can make some substitutions and deformations of some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present invention.
Claims
1. A motor overheat protection circuit, characterized in that: It includes a control circuit, which is connected to the alarm circuit and the relay circuit respectively; The control circuit includes a transistor V1, the base of the transistor V1 is connected to one end of a variable resistor RP and one end of a thermistor RT1, the other end of the variable resistor RP is connected to the alarm circuit, the other end of the thermistor RT1 is connected to one end of the thermistor RT2, the other end of the thermistor RT2 is connected to one end of the thermistor RT3, the other end of the thermistor RT3 is connected to one end of a resistor R3, and the other end of the resistor R3 is connected to the emitter of the transistor V1 and the emitter of the diode V2, respectively. The collector of transistor V1 is connected to the alarm circuit and one end of resistor R4 respectively. The other end of resistor R4 is connected to one end of resistor R5 and the base of transistor V2 respectively. The other end of resistor R5 is connected to one end of resistor R3 and the negative electrode of the power supply. The collector of transistor V2 is connected to the relay circuit. The alarm circuit includes a light-emitting diode VD1, the cathode of the light-emitting diode VD1 is connected to the negative electrode of the power supply, the anode of the light-emitting diode VD1 is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the other end of the variable resistor RP, the other end of the variable resistor is also connected to one end of the resistor R2, the other end of the resistor R2 is connected to the anode of the light-emitting diode VD2, and the cathode of the light-emitting diode VD2 is respectively connected to the collector of the transistor V1 and one end of the resistor R4; The relay circuit includes a relay K. One end of the coil of the relay K is connected to the collector of the transistor V2 and the positive electrode of the freewheeling diode VD3 respectively, and the other end of the coil of the relay K is connected to the positive electrode of the power supply and the negative electrode of the freewheeling diode VD3 respectively.
2. A motor overheat protection circuit according to claim 1, characterized in that: Thermistors RT1 , RT2 and RT3 have consistent characteristics and are evenly distributed in the stator winding of the motor.
3. A motor overheat protection circuit according to claim 2, characterized in that: The Curie temperatures of thermistors RT1, RT2, and RT3 are 40°C lower than the insulation temperature of the motor.