Air cooling structure of inverter and control method of inverter air duct self-cleaning

Abstract

The present invention discloses an air-cooled heat dissipation structure for a frequency converter and a control method for self-cleaning the frequency converter's air duct. The frequency converter includes a housing and a control circuit, the control circuit including a controller. The housing includes a cooling air duct, a radiator is provided in the cooling air duct, a fan is installed at one end of the cooling air duct's air outlet, and an air inlet window is installed at one end of the cooling air duct's air inlet. The fan is a bidirectional fan. The control circuit includes a fan forward and reverse drive circuit, a motor of the bidirectional fan is connected to the fan forward and reverse drive circuit, and a control terminal of the fan forward and reverse drive circuit is connected to the controller. The present invention can self-clean the cooling air duct by controlling the fan's reverse rotation, eliminating the need for a separate fan. The frequency converter is compact and low-cost.

Description

[Technical field]

[0001] The present invention relates to a frequency converter, and in particular to an air cooling and heat dissipation structure of the frequency converter and a control method for self-cleaning of the air duct of the frequency converter. [Background Technology]

[0002] As a crucial device for motor speed regulation, VFDs require a variety of protection circuits and mechanisms to ensure safe and reliable operation. Stable and effective operation of the VFD's heat dissipation system is crucial for reliable operation. Standard VFDs generally utilize fan cooling for heat dissipation. The heat sink is mounted vertically within the VFD's air duct, with the lower end of the duct serving as the air inlet and the upper end as the air outlet. The fan in the duct directs heat loss from power components adjacent to the heat sink out of the device. The fan then generates pressure and air volume, either blowing or drawing heat away from the heat sink's surface, thereby reducing the temperature of the internal power electronics and ensuring proper operation within acceptable limits.

[0003] In actual use, due to the harsh working environment, debris often blocks the air inlet of the air duct, resulting in insufficient air intake in the heat dissipation duct and overheating of the internal electronic power devices. In order to ensure the normal heat dissipation function of the inverter, the inverter heat dissipation duct needs to be manually cleaned.

[0004] For example, cotton wool, dust and other silky debris that are common in the textile industry environment are easily absorbed by the air inlet during the use of the inverter due to the airflow generated by the operation of the fan. Over time, the air inlet will be blocked, resulting in insufficient heat removed by the fan, causing thermal protection or failure of the electronic components inside the radiator, and the inverter will not work properly.

[0005] The utility model with patent number CN201820795971.3 discloses a special inverter for air-jet looms, including a main unit, a shell and a partition arranged inside the shell. The partition divides the shell into a main unit installation cavity and a cooling air duct. The main unit components of the inverter are installed in the main unit installation cavity, a heat sink is arranged inside the cooling air duct, a No. 1 fan is arranged at one end of the cooling air duct, and an air inlet filter is arranged at the other end of the cooling air duct; a No. 2 fan is arranged in the cooling air duct between the air inlet filter and the heat sink, and the No. 2 fan is located at one end close to the air inlet filter; this utility model can avoid air duct blockage by adding a No. 2 fan, but adding a fan will cause the inverter to increase in size and cost. [Summary of the invention]

[0006] The technical problem to be solved by the present invention is to provide an air-cooling heat dissipation structure for an inverter which does not require an additional fan and can still perform self-cleaning of the air duct.

[0007] The technical problem to be solved by the present invention is to provide a control method for self-cleaning of the air duct of the inverter with the above-mentioned air-cooling heat dissipation structure.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is an air-cooling heat dissipation structure of an inverter, including a housing and a control circuit of the inverter, the control circuit including a controller, the housing including a cooling air duct, a radiator provided in the cooling air duct, a fan installed at one end of the cooling air duct outlet, an air inlet window installed at one end of the cooling air duct inlet, and the fan is a bidirectional fan; the control circuit includes a fan forward and reverse drive circuit, the motor of the bidirectional fan is connected to the fan forward and reverse drive circuit, and the control end of the fan forward and reverse drive circuit is connected to the controller.

[0009] The air-cooling heat dissipation structure of the inverter described above has a control circuit including a cooling duct inlet temperature sensor and a radiator temperature sensor, and the signal output terminals of the cooling duct inlet temperature sensor and the radiator temperature sensor are respectively connected to the controller.

[0010] The air-cooling heat dissipation structure of the inverter described above, the fan forward and reverse drive circuit includes a fan motor power supply circuit and a fan motor control circuit, the fan motor power supply circuit includes a MOS tube, a first optocoupler and a fifth resistor, the motor power supply control signal output end of the controller is connected to the gate of the MOS tube through the first optocoupler; the drain of the MOS tube is connected to the positive pole of the motor power supply through the fifth resistor, and the source of the MOS tube is connected to the negative pole of the motor power supply; the positive input end of the fan motor is connected to the positive pole of the motor power supply, and the negative pole is connected to the drain of the MOS tube; the fan motor control circuit includes a transistor, a second optocoupler and a seventh resistor, the motor forward and reverse control signal output end of the controller is connected to the base of the transistor through the second optocoupler, the collector of the transistor is connected to the positive pole of the motor power supply through the seventh resistor, and the emitter of the transistor is connected to the negative pole of the motor power supply; the control end of the fan motor is connected to the collector of the transistor.

[0011] The air-cooling heat dissipation structure of the inverter described above, the fan motor power supply circuit includes a first voltage regulator tube and a diode, the cathode of the first voltage regulator tube is connected to the gate of the MOS tube, and the anode is connected to the source of the MOS tube; the anode of the diode is connected to the drain of the MOS tube, and the cathode is connected to the positive pole of the motor power supply; the fan motor control circuit includes a second voltage regulator tube, the anode of the second voltage regulator tube is connected to the emitter of the transistor, and the cathode is connected to the collector of the transistor.

[0012] A control method for self-cleaning of the inverter air duct adopts the air cooling and heat dissipation structure of the above-mentioned inverter and includes the following working steps: setting the reversal time of the fan in the self-cleaning mode; when the inverter enters the self-cleaning mode, the controller controls the bidirectional fan to reverse according to the set reversal time through the fan forward and reverse drive circuit, thereby realizing reverse air supply in the inverter cooling duct.

[0013] In the control method of the inverter described above, the self-cleaning mode is started and executed according to the system settings when the inverter is powered on, running and / or stopped; if the self-cleaning mode is executed when the inverter is powered on and / or running, after the fan reversal time is reached, the bidirectional fan rotates forward and the forward air supply is restored; if the self-cleaning mode is executed when the inverter is stopped, after the fan reversal time is reached, the bidirectional fan stops running.

[0014] The control method for the inverter described above includes a control circuit including a cooling duct inlet temperature sensor and a radiator temperature sensor, wherein the signal output terminal of the cooling duct inlet temperature sensor and the signal output terminal of the radiator temperature sensor are respectively connected to a controller; and includes the following working steps: comparing the temperature T1 of the cooling duct inlet with the temperature TH of the radiator, where the difference between T1 and TH is ΔT; when ΔT is greater than a set value and the radiator temperature TH is less than the radiator limit test value THmax, starting and executing the self-cleaning mode.

[0015] In the control method of the inverter described above, the execution time of the self-cleaning mode is controlled according to the temperature of the cooling air duct inlet; the higher the cooling air duct inlet temperature, the shorter the execution time of the self-cleaning mode; the lower the cooling air duct inlet temperature, the longer the execution time of the self-cleaning mode.

[0016] In the control method of the inverter described above, during the self-cleaning mode operation, the time for the bidirectional fan to reverse is Tcc, and the product of Tcc and T1 is the reference coefficient for the self-cleaning mode operation; at the end of the self-cleaning mode, if the product of Tcc and T1 is greater than the set value of the self-cleaning mode operation reference coefficient, the bidirectional fan switches to forward rotation; at the end of the self-cleaning mode, if the product of Tcc and T1 is still less than the set value of the self-cleaning mode operation reference coefficient, the self-cleaning mode is entered again.

[0017] When ΔT is greater than the set value, but the radiator temperature TH is greater than or equal to the radiator limit test value THmax, the controller records the status and automatically enters the post-shutdown self-cleaning mode when the inverter stops.

[0018] The present invention can self-clean the cooling air duct by controlling the fan to reverse, without adding an additional fan, and the frequency converter is small in size and low in cost. [Brief Description of the Drawings]

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 It is a cross-sectional view of the frequency converter according to the embodiment of the present invention.

[0021] Figure 2 It is a principle block diagram of the control circuit of an embodiment of the present invention.

[0022] Figure 3 4 is a circuit diagram of a fan motor power supply circuit according to an embodiment of the present invention.

[0023] Figure 4 4 is a circuit diagram of a fan motor control circuit according to an embodiment of the present invention.

[0024] Figure 5 This is a flow chart of the self-cleaning mode of the inverter in the standby state according to an embodiment of the present invention.

[0025] Figure 6 This is a flow chart of the self-cleaning mode in the inverter operation state according to an embodiment of the present invention. [Specific implementation method]

[0026] The structure of the frequency converter according to the embodiment of the present invention is as follows: Figures 1 to 4 As shown, the housing 10 includes a cooling duct M. The cooling duct M houses a heat sink 20 and a capacitor bank 60. The lower end of the cooling duct M serves as the cooling duct's air inlet, while the upper end serves as the cooling duct's air outlet. An air inlet window 30 is located at the air inlet, and a two-way fan 40 and a mesh cover 70 are located at the air outlet.

[0027] The windows 31 of the air inlet window 30 are arranged in a grid shape, and the lower ends of the fins 21 of the radiator 20 are against the air inlet window 30. The grid bars of the air inlet window 30 block the fins 21 of the radiator 20. The capacitor bank 60 is arranged between the radiator 20 and the fan 40.

[0028] like Figure 2 As shown, the control circuit of the inverter includes a controller, a fan forward and reverse drive circuit, a cooling air duct inlet temperature sensor and a radiator temperature sensor.

[0029] The motor of the bidirectional fan is connected to the fan forward and reverse driving circuit, and the control end of the fan forward and reverse driving circuit is connected to the controller.

[0030] The signal output end of the cooling air duct inlet temperature sensor and the signal output end of the radiator temperature sensor are connected to the controller respectively. Figure 1 As shown, the cooling air duct inlet temperature sensor is fixed on the air inlet window 30 , and the radiator temperature sensor 51 is fixed on the radiator 20 .

[0031] The fan forward and reverse drive circuit includes a fan motor power supply circuit and a fan motor control circuit.

[0032] The fan motor power supply circuit includes a MOS transistor M1, an optocoupler U1, a voltage regulator Z1, a diode D1, and a resistor R5. The controller's motor power control signal output is connected to the gate of MOS transistor M1 through the optocoupler U1. The drain of MOS transistor M1 is connected to the motor power supply's positive terminal VCC2 through resistor R5, while the source of MOS transistor M1 is connected to the motor power supply's negative terminal COM. The fan motor's positive input terminal is connected to the motor power supply's positive terminal VCC2, while the fan motor's negative terminal is connected to the drain of MOS transistor M1. The cathode of voltage regulator Z1 is connected to the gate of MOS transistor M1, while the anode is connected to the source of MOS transistor M1. The anode of diode D1 is connected to the drain of MOS transistor M1, while the cathode is connected to the motor power supply's positive terminal VCC2.

[0033] The fan motor control circuit includes transistor Q1, optocoupler U2, voltage regulator Z2, and resistor R7. The controller's motor forward and reverse control signal output is connected to the base of transistor Q1 through optocoupler U2. The collector of transistor Q1 is connected to the positive terminal of the motor power supply, VCC2, through resistor R7. The emitter of transistor Q1 is connected to the negative terminal of the motor power supply, COM. The fan motor control terminal is connected to the collector of transistor Q1. The anode of voltage regulator Z2 is connected to the emitter of transistor Q1, and the cathode is connected to the collector of transistor Q1.

[0034] like Figure 3 and Figure 4 As shown in the figure, the fan forward and reverse drive circuit has three output terminals, of which the "FAN+" terminal and the "FAN-" terminal are the fan power supply terminals. The "FAN-set" terminal is the motor forward and reverse control signal output terminal.

[0035] When the signal output from the "FAN-set" terminal is high relative to the level of the "FAN-" terminal, the fan rotates forward; when the signal output from the "FAN-set" terminal is low relative to the level of the "FAN-" terminal, the fan rotates reversely.

[0036] exist Figure 3 and Figure 4 In the figure, the FAN-A and FAN-B signals are provided by the controller. The FAN-A signal is the motor power control signal, and the FAN-B signal is the motor forward and reverse control signal. The low level of the FAN-A and FAN-B signals is valid.

[0037] The "FAN+" and "FAN-" terminals are connected to the fan power supply terminal. In the default state, there is no potential difference between the "FAN+" and "FAN-" terminals, and both are the positive voltage VCC2 of the motor power supply.

[0038] The "FAN-set" terminal is connected to the fan control terminal. In the default state, the voltage level of the "FAN-set" terminal is related to the Z2 voltage regulation value of the Zener diode.

[0039] When the inverter is running and the cooling system is required to operate normally, the controller outputs a low level for "FAN-A." The signal, after being isolated by an optocoupler, drives MOS transistor M1. The fan power port is then connected to the positive power supply VCC2 via the "FAN+" terminal. The level of the "FAN-" terminal is equivalent to the low level of the negative power supply COM, connecting the fan to the fan power supply.

[0040] When the controller's "FAN-B" signal is high, optocoupler U2 is off. Transistor Q1 is off, and the voltage at the "FAN-set" terminal is the regulator voltage of Zener diode Z1. When the fan is powered, the "FAN-set" signal is high, and the fan rotates forward.

[0041] When the "FAN-B" signal given by the controller is at a low level, the optocoupler U2 is turned on, causing the transistor Q1 to be turned on. At this time, the voltage output by the "FAN-set" terminal is pulled down to the low level of the negative electrode COM of the power supply by the transistor Q1. When the fan power is turned on, the "FAN-" level is close to the low level of the COM port, that is, the levels of "FAN-set" and "FAN-" are both low levels. The fan will stop in the forward direction and then start to reverse. Different fans have different switching times due to the different inertia of their fan blades.

[0042] If the "FAN+" and "FAN-" terminals are not connected to the motor power supply, the fan will not start.

[0043] When the bidirectional fan 40 rotates in the opposite direction, the cooling air flows from top to bottom, flowing in from the air outlet of the cooling air duct and out from the air inlet of the cooling air duct; the dust and cotton wool blocked on the air inlet window grille are subjected to the dual effects of downward thrust and their own gravity, and are peeled off by the reverse cooling air and blown away, thereby realizing self-cleaning of the cooling air duct.

[0044] The control method for self-cleaning of the inverter air duct in embodiment 1 of the present invention is as follows: Figure 5 As shown, the control method used is the simplest open-loop parameter setting control, requiring only the fan reverse time Tcc to be set in standby mode. The fan reverse time Tcc can be set from 15s to 30s. Because a bidirectional fan has a soft-start time during startup or switching, once the maximum reverse speed is reached, the fan must run for a certain period of time to reach the maximum speed and pressure. After the inverter is powered on, the internal parameters are checked to determine whether the three cleaning modes are set: power-on self-cleaning, self-cleaning during operation, and self-cleaning after shutdown. Figure 1As shown, it is mainly embodied in two ways: power-on self-cleaning and self-cleaning after shutdown. And these two judgment methods need to set the self-cleaning duration Tcc before the controller executes the operation command. Its characteristic is simple control, but in some applications, when it needs to start quickly after shutdown or startup, it cannot meet the application requirements.

[0045] The control method for self-cleaning of the inverter air duct in Embodiment 2 of the present invention is as Figure 6 shown. Embodiment 2 makes up for the deficiencies of Embodiment 1. Embodiment 2 can run the self-cleaning program during the operation of the inverter. The specific implementation method is that when the inverter is operating within the rated state, the controller detects the temperature T1 of the air inlet of the inverter device and the temperature TH of the radiator, and judges whether there is foreign matter blockage at the air inlet and whether self-cleaning mode needs to be performed by comparing the temperature difference ΔT between T1 and TH. The internal temperature difference reference value Tref of the controller can be set to 50°C. Then it is judged that when operating under normal rated conditions, when ΔT < 50°C, it is judged that the components in the inverter air duct can dissipate heat normally and there is no need to start the self-cleaning program; when ΔT > 50°C, it is judged that the self-cleaning process can be entered.

[0046] In addition, it should also be considered whether the radiator temperature TH exceeds its maximum value THmax. Since the THmax values of different specifications of inverters are different, this parameter is set to be adjustable, and the default THmax is 85°C. When TH > THmax = 85°C, due to the changes in air volume and air pressure during the forward and reverse rotation switching of the cooling fan, to ensure the thermal stability of the electronic components on the radiator. At this time, the self-cleaning mode is not entered temporarily (that is, the fan switches from forward rotation to reverse rotation state), and the controller records the state. When the inverter stops, it automatically enters the self-cleaning mode after shutdown, that is, the process described in Embodiment 1. When TH < THmax, the controller determines that the inverter device can perform the air duct self-cleaning mode. At this time, the inverter can operate stably, and the rotation direction of the fan changes from forward rotation to reverse rotation (the self-cleaning mode starts), and the length of the reverse rotation time Tcc is inversely proportional to the change in the air inlet temperature T1. Its purpose is to take the heat on the radiator to the fluffs and dust blocked at the air inlet, making it bear thermal stress for easy cleaning. Here, it is defined that Tcc × T1 = Kref (self-cleaning mode operation reference coefficient). The set value of the self-cleaning mode operation reference coefficient Kref is 1800, which means that when the air inlet temperature is 60°C, the self-cleaning time lasts for 30 seconds. For different inverters, due to different air ducts, the Kref value can be set to different values, which can be determined according to the specific cleaning time required.

[0047] During the self-cleaning process, when Tcc×T1 is greater than or equal to the set Kref, it indicates that the self-cleaning is complete. At this time, the fan of the inverter equipment switches to forward operation. When Tcc×T1 is less than the set Kref, it is necessary to enter the self-cleaning mode again.

[0048] The cleaning mode of the above embodiment of the present invention solves the problem of clogging of the variable frequency air duct opening, does not require manual maintenance, and does not require the design of a frequency converter with other heat dissipation methods, which has high economic benefits for users or manufacturers.

Claims

1. A control method for self-cleaning of an inverter air duct, characterized in that: The inverter includes a shell and a control circuit, the control circuit includes a controller, the shell includes a cooling air duct, a radiator is provided in the cooling air duct, a fan is installed at one end of the cooling air duct outlet, and an air inlet window is installed at one end of the cooling air duct inlet, and the fan is a bidirectional fan; the control circuit includes a fan forward and reverse drive circuit, the motor of the bidirectional fan is connected to the fan forward and reverse drive circuit, and the control end of the fan forward and reverse drive circuit is connected to the controller; the control circuit includes a cooling air duct inlet temperature sensor and a radiator temperature sensor, and the signal output end of the cooling air duct inlet temperature sensor and the signal output end of the radiator temperature sensor are respectively connected to the controller; the self-cleaning control method includes the following working steps: setting the reversal time of the fan in the self-cleaning mode, when the inverter enters the self-cleaning mode, the controller controls the reversal of the bidirectional fan through the fan forward and reverse drive circuit according to the set reversal time, thereby realizing reverse air supply in the inverter cooling air duct; Compare the temperature T1 of the cooling air duct inlet and the temperature TH of the radiator, and the difference between T1 and TH is ΔT; when ΔT is greater than the set value and the radiator temperature TH is less than the radiator limit test value THmax, the self-cleaning mode is started and executed; during the self-cleaning mode, the reversal time of the two-way fan is Tcc, and the product of Tcc and T1 is the reference coefficient for the self-cleaning mode operation; at the end of the self-cleaning mode, if the product of Tcc and T1 is greater than the set value of the self-cleaning mode operation reference coefficient, the two-way fan switches to forward operation; at the end of the self-cleaning mode, if the product of Tcc and T1 is still less than the set value of the self-cleaning mode operation reference coefficient, the self-cleaning mode is entered again.

2. The control method according to claim 1, characterized in that: The fan forward and reverse drive circuit includes a fan motor power supply circuit and a fan motor control circuit. The fan motor power supply circuit includes a MOS tube, a first optocoupler and a fifth resistor. The motor power supply control signal output end of the controller is connected to the gate of the MOS tube through the first optocoupler; the drain of the MOS tube is connected to the positive electrode of the motor power supply through the fifth resistor, and the source of the MOS tube is connected to the negative electrode of the motor power supply; the positive input end of the fan motor is connected to the positive electrode of the motor power supply, and the negative electrode is connected to the drain of the MOS tube; the fan motor control circuit includes a transistor, a second optocoupler and a seventh resistor. The motor forward and reverse control signal output end of the controller is connected to the base of the transistor through the second optocoupler, the collector of the transistor is connected to the positive electrode of the motor power supply through the seventh resistor, and the emitter of the transistor is connected to the negative electrode of the motor power supply; the control end of the fan motor is connected to the collector of the transistor.

3. The control method according to claim 2, characterized in that: The fan motor power supply circuit includes a first voltage regulator tube and a diode, wherein the cathode of the first voltage regulator tube is connected to the gate of the MOS tube, and the anode is connected to the source of the MOS tube; the anode of the diode is connected to the drain of the MOS tube, and the cathode is connected to the positive electrode of the motor power supply; the fan motor control circuit includes a second voltage regulator tube, wherein the anode of the second voltage regulator tube is connected to the emitter of the transistor, and the cathode is connected to the collector of the transistor.

4. The control method according to claim 1, wherein: The self-cleaning mode is activated and executed according to the system settings when the inverter is powered on, running and / or stopped. If the self-cleaning mode is executed when the inverter is powered on and / or running, the bidirectional fans will rotate forward after the fan reverse rotation time is reached, and forward air supply will be restored. If the self-cleaning mode is executed when the inverter is stopped, the bidirectional fans will stop running after the fan reverse rotation time is reached.

5. The control method according to claim 1, characterized in that: The execution time of the self-cleaning mode is controlled according to the temperature of the cooling air duct inlet. The higher the cooling air duct inlet temperature, the shorter the execution time of the self-cleaning mode; the lower the cooling air duct inlet temperature, the longer the execution time of the self-cleaning mode.

6. The control method according to claim 1, characterized in that: When ΔT is greater than the set value, but the radiator temperature TH is greater than or equal to the radiator limit test value THmax, the controller records the status and automatically enters the post-shutdown self-cleaning mode when the inverter stops.

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