CN211981487U - Hardware thermal protection circuit structure of frequency converter - Google Patents

Abstract

The utility model discloses a converter hardware thermal protection circuit structure, alternating current power supply generates the direct current through rectifier circuit 1, this direct current produces the changeable alternating current driving motor of voltage frequency through inverter circuit, contain a temperature sensing element in the inverter circuit, the signal that this temperature sensing element produced controls electronic switch through the trigger circuit, this electronic switch is arranged between switching power supply and main control chip, control switching power supply to main control chip's power supply; or the electronic switch is arranged between the inverter circuit and the main control chip and controls the main control chip to transmit PWM signals to the inverter circuit; or the electronic switch is arranged between the alternating current power supply and the rectification circuit 1 and is controlled by a trigger circuit which is formed by a second rectification circuit and a switching power supply and is powered by an independent power supply. The utility model realizes the overheat protection of the controller and the motor completely by a hardware circuit, and does not depend on software; there is no need to embed a thermal protector in the motor coil.

Description

Hardware thermal protection circuit structure of frequency converter

Technical Field

The utility model belongs to the technical field of motor speed control system and specifically relates to hot protection circuit structure of converter hardware.

Background

In a motor speed regulating system, the current of a motor and a driving controller is increased and the temperature rise is overhigh due to the reasons of motor overload, locked rotor and the like, so that the overheating protection is an extremely important technical content in the motor speed regulating system. In UL product safety certification, motor stalling is a necessary test item, and high temperature generated during motor stalling examination cannot damage a motor and a driver, and particularly cannot cause combustion. In the UL certification test, if the over-temperature protection relates to software control, the UL will perform extremely strict and careful auditing on the corresponding source code of the product, resulting in extremely complicated certification procedures, long time and high cost. Therefore, many products seek to replace software protection with a hardware protection mode so as to smoothly and quickly pass the UL authentication, and even if the UL authentication is not performed, in practical application, a pure hardware thermal protection mode is superior to a pure software protection mode, so that the problem of failure of the protection function caused by software error or program runout can be avoided.

There are three common methods of overheat protection, the first is to place a thermal protector inside the motor, the second is to provide a separate temperature sensor at the controller, and the third is to use a heat sensitive element integrated in the semiconductor power device. The first method is that the thermal protector is tightly attached to the surface of the motor coil, the outgoing wires at two ends of the thermal protector are directly connected with the motor coil in series or are led out to be connected to the power input end of the controller, and when the temperature of the coil is too high, the protector acts to disconnect the electrical connection. The former can only protect the motor, and the latter can protect the whole speed regulating system. The second and third methods generally input the signal of a temperature sensor or a thermistor into a single chip, and the single chip controls the system according to the temperature rise. In some occasions, the internal resistance of a motor coil is small, the controller and the motor are integrally installed, the motor is not rotated by a fan when the motor is locked, the temperature rise of the coil generated by the current of the motor is not increased, and the thermal protector in the first method is probably not operated and cannot play a role in protection. In the latter two methods, the main chip controls the switch of the power element according to the signal voltage, the control is usually completed by a software algorithm, if the program of the main chip makes mistakes, the system will be out of control, and the protection cannot be realized when overheating and overtemperature happen.

SUMMERY OF THE UTILITY MODEL

For solving the above-mentioned problem that common overheat protection method exists, the utility model provides a converter hardware thermal protection circuit structure.

In order to achieve the above purpose, the utility model adopts the following technical scheme:

the hardware thermal protection circuit structure of the frequency converter, the alternating current power supply produces the direct current through the rectifier circuit 1, the direct current produces the variable alternating current driving motor of voltage frequency through the inverter circuit, include a heat-sensitive component in the inverter circuit, the signal that the heat-sensitive component produces controls the electronic switch through the trigger circuit, the electronic switch is placed between switching power supply and main control chip, control the switching power supply to the power supply of the main control chip; or the electronic switch is arranged between the inverter circuit and the main control chip and controls the main control chip to transmit PWM signals to the inverter circuit; or the electronic switch is arranged between the alternating current power supply and the rectification circuit 1 and is controlled by a trigger circuit which is formed by a second rectification circuit and a switching power supply and is powered by an independent power supply.

Further, the intelligent power supply comprises an alternating current power supply, a rectifying circuit 1, an inverter circuit, a motor, a trigger circuit, a switching power supply, an electronic switch and a main control chip, wherein the alternating current power supply, the rectifying circuit 1 and the inverter circuit are sequentially connected with the motor, the inverter circuit comprises a thermosensitive element, the thermosensitive element and the trigger circuit are sequentially connected with the electronic switch, the rectifying circuit 1 is further connected with the switching power supply, the switching power supply and the electronic switch are sequentially connected with the main control chip, the main control chip is interconnected with the inverter circuit, and the switching power supply is further connected with the trigger circuit.

Further, the motor comprises an alternating current power supply, a rectifying circuit 1, an inverter circuit, a motor, a trigger circuit, a switching power supply, an electronic switch and a main control chip, wherein the alternating current power supply, the rectifying circuit 1 and the inverter circuit are sequentially connected with the motor, the inverter circuit comprises a thermosensitive element, the thermosensitive element and the trigger circuit are sequentially connected with the electronic switch, the main control chip and the electronic switch are sequentially interconnected with each other, the rectifying circuit 1 is also connected with the switching power supply, and the switching power supply is respectively connected with the trigger circuit and the main control chip.

Further, the motor comprises an alternating current power supply, a rectification circuit 1, an inverter circuit, a motor, a trigger circuit, a switching power supply, an electronic switch and a second rectification circuit, wherein the alternating current power supply, the electronic switch, the rectification circuit 1 and the inverter circuit are sequentially connected with the motor, the inverter circuit comprises a thermosensitive element, the thermosensitive element and the trigger circuit are sequentially connected with the electronic switch, the alternating current power supply is also connected with the second rectification circuit, and the second rectification circuit and the switching power supply are sequentially connected with the trigger circuit.

Has the advantages that:

1. the utility model discloses realize the overheat protection to controller and motor by hardware circuit completely, do not rely on software.

2. The utility model discloses need not bury the hot protector underground in the electric machine coil, simplify motor production technology and save material.

Drawings

Fig. 1 is a block diagram of a first thermal protection circuit of the present invention;

fig. 2 is a schematic diagram of a thermal protection circuit according to an embodiment of the present invention;

fig. 3 is a block diagram of a second thermal protection circuit according to the present invention;

FIG. 4 is a schematic diagram of a second thermal protection circuit according to an embodiment of the present invention;

fig. 5 is a block diagram of a third thermal protection circuit according to the present invention;

fig. 6 is a structure diagram of a thermal protection circuit according to an embodiment of the present invention;

in the figure: the device comprises an alternating current power supply 1, a rectification circuit 2, an inverter circuit 3, a motor 4, a switch power supply 5, a thermosensitive element 6, a trigger circuit 7, an electronic switch 8, a main control chip 9 and a second rectification circuit 10.

Detailed Description

The present invention will be further explained with reference to the drawings and examples.

The utility model provides a three kinds of circuit structures that utilize the temperature sensing element of integrated or independent setting to carry out hardware overheat protection in the controller.

The first method comprises the following steps: the power to the main chip in the controller is turned off as shown in fig. 1. In fig. 1, an alternating current power supply 1 generates direct current through a rectification circuit 12, the direct current generates alternating current electric drive motor 4 with variable voltage and frequency through an inverter circuit 3, the inverter circuit 3 comprises a thermosensitive element 5, a signal generated by the thermosensitive element 5 controls an electronic switch 8 through a trigger circuit 6, and the electronic switch 8 controls a switch power supply 7 to supply power to a main control chip 9. When the temperature rises to the protection limit value, the signal generated by the thermosensitive element 5 enables the trigger circuit 6 to act, the electronic switch 8 is turned off, the main control chip 9 stops working due to power loss, and the motor 4 stops working. When the temperature drops, the electronic switch 8 is switched on, the main control chip 9 is powered on to work, and the motor 4 is restarted to run.

And the second method comprises the following steps: and disconnecting a signal link from the main chip to the power switch tube (IGBT, MOS tube, thyristor, etc.), and stopping the power switch tube from working, as shown in FIG. 3. The basic principle is similar to the first one, except that the electronic switch 8 is arranged between the main control chip 9 and the inverter circuit 3, and controls the transmission of the PWM signal from the main control chip 9 to the inverter circuit 3. When the temperature rises to reach the protection limit value, the signal generated by the thermosensitive element 5 enables the trigger circuit 6 to act, and the electronic switch 8 is turned off, so that the PWM signal is cut off, the inverter circuit 3 stops working, and the motor 4 is stopped. When the temperature is reduced, the electronic switch 8 is switched on to obtain a signal, the inverter circuit 3 obtains the signal to work again, and the motor 4 is recovered to operate.

The utility model discloses in, electronic switch 8 and thermistor 5's power and main control chip 9's power supply are each other not electrically connected, prevent that protection circuit from losing the electricity because of circuit protection is permanent, can not automatic recovery work.

And the third is that: the motor controller main loop power supply is disconnected as shown in fig. 5. An electronic switch 8 is arranged between an alternating current power supply 1 and a rectification circuit 12 of a main loop, the electronic switch 8 is controlled by a trigger circuit 6 powered by an independent power supply (a second rectification circuit 10 and a switching power supply 7), when the temperature rises to reach a protection limit value, a signal generated by a thermosensitive element 5 enables the trigger circuit 6 to act, and the electronic switch 8 is turned off, so that the power supply of the main loop is cut off, and the motor 4 is stopped. When the temperature drops, the electronic switch 8 is switched on, the main loop recovers power supply, and the system is restarted.

The utility model discloses in, can arrange three kinds of hardware overheat protection circuit structure in electronic switch's position in with an independent temperature switch, replace thermistor 5, trigger circuit 6 and electronic switch 8 among the above-mentioned three kinds of hardware overheat protection circuit structure.

The first embodiment is as follows: turning off the power supply of the main control chip (DSP or MCU)

As shown in fig. 2, the power source VC3 of the main control chip U2 is connected to the control board auxiliary power source VC2 (direct output of the switching power source or output of the switching power source after passing through the LDO precision voltage reduction device) through an electronic switch Q1 such as a triode, a MOS transistor, a relay, etc., ON/OFF of the electronic switch Q1 is controlled by a comparator U1 circuit, one input of the comparator U1 is connected to the thermistor NTC, the other input is connected to a reference voltage, and the reference voltage is generated by the VC2 through voltage division by two precision resistors R2, R3 and serves as a threshold voltage for NTC temperature protection. Along with the rise of the temperature, the resistance value of the NTC is reduced, when the voltage on the NTC is reduced to be lower than the reference voltage, the output level of the comparator is reversed, the electronic switch Q1 is controlled to be turned off, the main control chip U2 is powered off, no voltage is output to the motor M1 by the inverter circuit PM1 due to the loss of the control signal, and the motor M1 is stopped. When the temperature gradually decreases, the resistance value of the NTC increases, and the voltage on the NTC exceeds the reference voltage, the output level of the comparator U1 is inverted again, the electronic switch Q1 is controlled to be switched on, the MCU is powered on to recover to work, and the motor M1 is restarted to run. The resistor R4 forms a hysteresis circuit of the comparator U1, and is used for generating a window of output level inversion action of the comparator U1, so that the NTC output level is not frequently inverted when the voltage generated by the NTC falls near the reference voltage, and power supply oscillation and unstable system operation of the main control chip U2 are avoided.

Second embodiment two: PWM signal sent to inverter circuit by switching off main control chip

As shown in fig. 4, the basic principle is the same as that of the first embodiment, the in-phase device U5 is disposed in the PWM signal circuit of the main control chip U2 and the inverter circuit PM1, when the temperature sensed by the thermistor NTC is higher than the reference protection value, the output of the comparator U1 is reversed, the signal link in the in-phase device U5 is disconnected, the inverter circuit PM1 has no output voltage to the motor M1 due to signal loss, and the motor M1 is stopped. When the temperature of the thermistor NTC is reduced, the output of the comparator U1 is reversed, so that a signal link in the in-phase device U5 is connected, the inverter circuit PM1 works again, and the motor M1 resumes operation.

Third embodiment three: turning off the main loop power supply

As shown in fig. 6, an auxiliary control power supply U3 is provided at the ac input end independently of the main power supply of the controller, in an isolated or non-isolated manner, for supplying power to the NTC temperature sampling circuit and the main circuit electronic switch U2 (relay, thyristor), when the NTC temperature is higher than the temperature protection threshold point, the output level of the comparator U1 is inverted, so that the transistor Q1 is turned off, and the electronic switch U2 is also turned off due to the loss of the control power supply, so that the entire main circuit is powered off; when the NTC temperature drops below the protection threshold point, the output level of the comparator U1 is inverted again, so that the electronic switch U2 is turned on, and the main power supply of the controller is electrified to recover the work.

To the limitation of the protection scope of the present invention, it should be understood by those skilled in the art that, on the basis of the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

Claims (4)

1. Frequency converter hardware thermal protection circuit structure, alternating current power supply (1) generate the direct current through rectifier circuit 1(2), and this direct current passes through inverter circuit (3) and produces changeable alternating current driving motor (4) of voltage frequency, its characterized in that: the inverter circuit (3) comprises a thermosensitive element (5), a signal generated by the thermosensitive element (5) controls an electronic switch (8) through a trigger circuit (6), the electronic switch (8) is arranged between a switching power supply (7) and a main control chip (9), and the switching power supply (7) is controlled to supply power to the main control chip (9); or the electronic switch (8) is arranged between the inverter circuit (3) and the main control chip (9) to control the transmission of the PWM signal from the main control chip (9) to the inverter circuit (3); or the electronic switch (8) is arranged between the alternating current power supply (1) and the rectifying circuit 1(2), and the electronic switch (8) is controlled by a trigger circuit (6) which is formed by a second rectifying circuit (10) and a switching power supply (7) and is powered by an independent power supply.

2. The converter hardware thermal protection circuit structure of claim 1, wherein: the intelligent energy-saving control circuit comprises an alternating current power supply (1), a rectifying circuit 1(2), an inverter circuit (3), a motor (4), a trigger circuit (6), a switching power supply (7), an electronic switch (8) and a main control chip (9), wherein the alternating current power supply (1), the rectifying circuit 1(2), the inverter circuit (3) and the motor (4) are sequentially connected, a thermosensitive element (5) and the trigger circuit (6) are sequentially connected with the electronic switch (8), the rectifying circuit 1(2) is also connected with the switching power supply (7), the switching power supply (7) and the electronic switch (8) are sequentially connected with the main control chip (9), the main control chip (9) is interconnected with the inverter circuit (3), and the switching power supply (7) is also connected with the trigger circuit (6).

3. The converter hardware thermal protection circuit structure of claim 1, wherein: the intelligent energy-saving control circuit comprises an alternating current power supply (1), a rectifying circuit (1) (2), an inverter circuit (3), a motor (4), a trigger circuit (6), a switching power supply (7), an electronic switch (8) and a main control chip (9), wherein the alternating current power supply (1), the rectifying circuit (1) (2), the inverter circuit (3) and the motor (4) are sequentially connected, a thermosensitive element (5), the trigger circuit (6) and the electronic switch (8) are sequentially connected, the main control chip (9), the electronic switch (8) and the thermosensitive element (5) are sequentially interconnected, the rectifying circuit (1) (2) is further connected with the switching power supply (7), and the switching power supply (7) is respectively connected with the trigger circuit (6) and the main control chip (9).

4. The converter hardware thermal protection circuit structure of claim 1, wherein: the intelligent energy-saving control circuit comprises an alternating current power supply (1), a rectifying circuit (1) (2), an inverter circuit (3), a motor (4), a trigger circuit (6), a switching power supply (7), an electronic switch (8) and a second rectifying circuit (10), wherein the alternating current power supply (1), the electronic switch (8), the rectifying circuit (1) (2), the inverter circuit (3) and the motor (4) are sequentially connected, a thermosensitive element (5), the trigger circuit (6) and the electronic switch (8) are sequentially connected, the alternating current power supply (1) is further connected with the second rectifying circuit (10), and the second rectifying circuit (10), the switching power supply (7) and the trigger circuit (6) are sequentially connected.

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