Bulk curing barn circulating fan control device

Abstract

The utility model discloses a bulk curing barn circulating fan control device, which comprises a frequency converter, a configuration screen and a power supply switching circuit, and is characterized in that a three-phase power supply access end group of the frequency converter is connected with a fan high-speed winding wiring terminal strip and a fan low-speed winding wiring terminal strip of a curing barn controller through the power supply switching circuit; a fan high-speed winding terminal block and a fan low-speed winding terminal block of the curing barn controller supply power to a frequency converter, an automatic control end group of the frequency converter is connected with a configuration screen, and the configuration screen is connected with a multipurpose curing barn temperature sensor. A three-phase power supply output end group of the frequency converter is connected with a high-speed winding connection terminal strip of the circulating fan, and a low-speed winding connection terminal strip of the circulating fan is in short circuit; and the configuration screen controls the circulating fan to work through the frequency converter according to a signal of the multipurpose curing barn temperature sensor. According to the utility model, the curing barn controller does not need to be upgraded and replaced, and automatic frequency conversion speed regulation of the circulating fan is realized.

Description

Technical Field

[0001] This utility model relates to the technical field of intensive drying room equipment, and in particular to a control device for the circulating fan of an intensive drying room. Background Technology

[0002] Currently, tobacco curing is mainly carried out in intensive curing barns. These barns are equipped with a controller that regulates temperature, humidity, and airflow by controlling the heating, dehumidification, and circulating fans. Circulating fans come in single-phase and three-phase types. The three-phase fans all employ a dual-winding structure, allowing for both high and low speed settings. The corresponding barn controller has a winding switching switch, which is currently operated manually.

[0003] To improve baking quality, some baking ovens use oven controllers with variable frequency control (VFD) functions. The oven controller outputs control commands to the VFD to achieve continuous adjustment of the fan speed. However, this method requires the redevelopment or upgrading of the existing oven controller hardware and software. Furthermore, due to the wide variety of VFD models, the oven controller needs to modify its software to match each VFD, which hinders the widespread application of VFDs.

[0004] Due to the large number of existing conventional high-density drying oven controllers, replacement and upgrade costs are high. Currently, the commonly used frequency converters are individually powered, and the drying oven controller is connected to the frequency converter via a communication line to send control commands. This presents the following problems:

[0005] (1) Communication connection between the oven controller and the frequency converter. The communication protocols of frequency converters from different manufacturers and brands are different. Therefore, the oven controller needs to design a special control program for different models of frequency converters, which results in a large development workload for oven controller manufacturers. Some oven controllers do not even have reserved communication interfaces, making it difficult to promote this solution on a large scale.

[0006] (2) The circulating fan current does not pass through the oven controller, which means that the oven controller cannot directly collect the fan current. When the oven controller cannot detect the fan current, it will issue an alarm signal by default. Therefore, the operator needs to turn off the current alarm function. For controllers without an alarm shutdown function, the alarm signal will continue to be issued.

[0007] Therefore, designing a fan controller that does not require upgrading or replacing the oven controller and can simultaneously achieve automatic frequency conversion speed regulation of the circulating fan is of practical use. Utility Model Content

[0008] In view of at least one deficiency of the prior art, the purpose of this utility model is to provide a control device for the circulating fan of a dense drying oven, which can realize automatic frequency conversion speed regulation of the circulating fan without upgrading or replacing the drying oven controller.

[0009] To achieve the above objectives, this utility model adopts the following technical solution: a control device for a circulating fan in a dense drying oven, comprising a frequency converter and a configuration panel, and further comprising a power switching circuit. The three-phase power input terminal group of the frequency converter is connected to the high-speed winding terminal block and the low-speed winding terminal block of the fan of the drying oven controller via the power switching circuit. The high-speed winding terminal block and the low-speed winding terminal block of the fan of the drying oven controller supply power to the frequency converter. The automatic control terminal group of the frequency converter is connected to the configuration panel, and the configuration panel is connected to a multi-purpose drying oven temperature sensor. The three-phase power output terminal group of the frequency converter is connected to the high-speed winding terminal block of the circulating fan, and the low-speed winding terminal block of the circulating fan is short-circuited. The configuration panel controls the operation of the circulating fan via the frequency converter based on the signal from the multi-purpose drying oven temperature sensor.

[0010] During the baking process in a dense baking oven, the speed of the circulating fan is generally determined by the temperature of the oven. Typically, it is set to low speed (960 rpm) below 42 degrees Celsius, high speed (1440 rpm) in the range of 42-54 degrees Celsius, and low speed (960 rpm) above 54 degrees Celsius. This temperature setting method is the conventional setting method.

[0011] The power switching circuit includes relays;

[0012] The UCH terminal of the high-speed winding terminal block of the fan is connected to the UC terminal of the three-phase power input terminal group of the frequency converter via the normally open switch of the first main switch of the relay. The UCL terminal of the low-speed winding terminal block of the fan is connected to the UC terminal of the three-phase power input terminal group of the frequency converter via the normally closed switch of the first main switch of the relay.

[0013] The VCH terminal of the high-speed winding terminal block of the fan is connected to the VC terminal of the three-phase power input terminal group of the frequency converter via the normally open switch of the second main switch of the relay. The VCL terminal of the low-speed winding terminal block of the fan is connected to the VC terminal of the three-phase power input terminal group of the frequency converter via the normally closed switch of the second main switch of the relay.

[0014] The WCH terminal of the high-speed winding terminal block of the fan is connected to the WC terminal of the three-phase power input terminal group of the frequency converter via the normally open switch of the third main switch of the relay. The WCL terminal of the low-speed winding terminal block of the fan is connected to the WC terminal of the three-phase power input terminal group of the frequency converter via the normally closed switch of the third main switch of the relay.

[0015] The relay's control coil is connected to any two of the UCH, VCH, and WCH terminals.

[0016] One end of the normally closed switch of the fourth main switch of the relay is connected to a DC power supply, and the other end of the normally closed switch of the fourth main switch is connected to the manual control terminal TIN of the frequency converter.

[0017] It also includes a power conversion circuit, whose two input terminals are connected to the UC terminal and the VC terminal respectively, and whose output terminal is connected to one end of the normally closed switch of the fourth main switch to provide the DC power. The power conversion circuit also supplies power to the configuration panel and the multi-purpose oven temperature sensor.

[0018] Significant effect: This utility model provides a control device for the circulating fan of a dense drying oven, which eliminates the need to upgrade or replace the drying oven controller and realizes automatic frequency conversion speed regulation of the circulating fan. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the fan controller connection for a standard drying room;

[0020] Figure 2 This is a connection diagram for the fan controller;

[0021] Figure 3 This is a schematic diagram of the structure of the wind turbine controller;

[0022] Figure 4 The diagram shows the connection between the oven controller and the power supply switching circuit, where (a) is the fan terminal of the oven controller; and (b) is the circuit diagram of the power supply switching circuit.

[0023] Figure 5 This is a wiring diagram of the frequency converter and the circulating fan; where (a) is the power supply terminal of the frequency converter; (b) is the motor interface of the frequency converter; and (c) is a wiring diagram of the high-speed winding connection terminal block and the low-speed winding connection terminal block of the circulating fan.

[0024] Figure 6 For the communication interface and switch interface of the frequency converter;

[0025] Figure 7 This is a circuit diagram for the temperature sensor interface.

[0026] Figure 8 This is a circuit diagram of a power conversion circuit;

[0027] Figure 9 The circuit diagram for the alarm interface;

[0028] Figure 10 This is a flowchart of the temperature difference measurement process for the configuration panel.

[0029] Figure 11 The process for adjusting the rotation speed of the configuration screen;

[0030] Figure 12 This describes the forward and reverse rotation switching process for the circulating fan. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0032] Existing oven controllers do not have inverter functionality and can only perform manual switching control of the circulating fan windings. To achieve variable frequency control of the fan, an external inverter is required. Currently, the conventional method is as follows: Figure 1 As shown, the frequency converter is powered independently, and the oven controller is connected to the frequency converter via a communication line and sends control commands to the frequency converter.

[0033] like Figures 1-12 As shown, this utility model relates to a control device for the circulating fan of a dense drying oven, namely a fan controller. The connection method adopted by this utility model is as follows: Figure 2 As shown, the frequency converter is replaced with a fan controller with the frequency converter as the core component, and components such as a multi-purpose drying oven temperature sensor, configuration panel, and alarm are added. Figure 3 This is a schematic diagram of the structure of a wind turbine controller.

[0034] 1. Connection method. The fan controller draws power from the fan terminal of the oven controller. The oven controller can collect the circulating fan current and will not trigger a "no fan current" alarm.

[0035] In terms of connection method, the fan controller is connected in series between the oven controller and the circulating fan. The power supply is connected to the circulating fan after passing through the oven controller and the fan controller. Therefore, the oven controller can normally collect the current of the circulating fan and the oven controller will not have a "no current in fan" alarm.

[0036] The following section will describe this device in detail, focusing on its circuit diagram. Figure 4 The diagram shows the connection between the oven controller and the power supply switching circuit. In this diagram, (a) is the fan terminal block of the oven controller. The high-speed winding terminal block of the fan of the oven controller is equipped with three terminals: UCH, VCH, and WCH. The low-speed winding terminal block of the fan is equipped with three terminals: UCL, VCL, and WCL.

[0037] (b) is the circuit diagram of the power supply switching circuit; where the three terminals UC, VC, and WC are the three-phase power supply input terminals of the frequency converter;

[0038] Figure 5This is a wiring diagram of the frequency converter and the circulating fan; where (a) is the power supply terminal of the frequency converter, and the three-phase power input terminal group of the frequency converter is UC, VC, WC; (b) is the motor interface of the frequency converter; its three terminals are connected to the three terminals U2, V2, W2 of the high-speed winding connection terminal block of the circulating fan; (c) is a wiring diagram of the high-speed winding connection terminal block and the low-speed winding connection terminal block of the circulating fan; the frequency conversion speed regulation of the circulating fan motor is controlled by the three terminals U2, V2, W2 of the high-speed winding connection terminal block of the circulating fan, and the three terminals U1, V1, W1 of the low-speed winding connection terminal block of the circulating fan are shorted together.

[0039] Figure 6 This is the communication interface and switch interface for the frequency converter; the frequency converter is connected to the configuration panel via RS485A and RS485B, and its signal output terminal TB is connected to the alarm to control its alarm.

[0040] Figure 7 This is a circuit diagram of the temperature sensor interface; the multi-purpose drying oven temperature sensor is connected to the configuration panel via RS485A and RS485B. The multi-purpose drying oven temperature sensor can be a DHT11 temperature and humidity sensor, etc.

[0041] Figure 8 This is a circuit diagram of a power conversion circuit. The input terminals of its main control chip are connected to UC and VC in the three-phase power input terminals of the frequency converter; it outputs 24V DC power.

[0042] Figure 9 This is the circuit diagram for the alarm interface; the inverter is connected via the TB terminal.

[0043] like Figures 2-9 As shown, this utility model includes a frequency converter and a configuration panel, as well as a power switching circuit. The three-phase power input terminals (UC, VC, WC) of the frequency converter are connected to the high-speed winding terminal blocks (UCH, VCH, WCH) and low-speed winding terminal blocks (UCL, VCL, WCL) of the fan of the drying oven controller via the power switching circuit. The inverter is powered by an RS485A and RS485B automatic control terminal group. A configuration panel is connected to the inverter, and the configuration panel is connected to a multi-purpose oven temperature sensor via RS485A and RS485B. The inverter's three-phase power output terminal group is connected to the high-speed winding terminal block (U2, V2, W2) of the circulating fan, and the low-speed winding terminal block (U1, V1, W1) of the circulating fan is short-circuited. The configuration panel controls the operation of the circulating fan via the inverter based on the signal from the multi-purpose oven temperature sensor.

[0044] The configuration panel is a mature product, model TPC7012EL, and its detailed structure will not be described further. The frequency converter is also a mature product.

[0045] The multi-purpose oven temperature sensor is used to detect the temperature inside the dense oven and send it to the configuration panel.

[0046] During the baking process in a dense baking oven, the speed of the circulating fan is generally determined by the temperature of the oven. Typically, it is set to low speed (960 rpm) below 42 degrees Celsius, high speed (1440 rpm) in the range of 42-54 degrees Celsius, and low speed (960 rpm) above 54 degrees Celsius. This temperature setting method is the conventional setting method.

[0047] The power switching circuit includes relay RLY1;

[0048] The UCH terminal of the high-speed winding terminal block of the fan is connected to the UC terminal of the three-phase power input terminal group of the frequency converter via the normally open switch of the first main switch of the relay. The UCL terminal of the low-speed winding terminal block of the fan is connected to the UC terminal of the three-phase power input terminal group of the frequency converter via the normally closed switch of the first main switch of the relay.

[0049] The VCH terminal of the high-speed winding terminal block of the fan is connected to the VC terminal of the three-phase power input terminal group of the frequency converter via the normally open switch of the second main switch of the relay. The VCL terminal of the low-speed winding terminal block of the fan is connected to the VC terminal of the three-phase power input terminal group of the frequency converter via the normally closed switch of the second main switch of the relay.

[0050] The WCH terminal of the high-speed winding terminal block of the fan is connected to the WC terminal of the three-phase power input terminal group of the frequency converter via the normally open switch of the third main switch of the relay. The WCL terminal of the low-speed winding terminal block of the fan is connected to the WC terminal of the three-phase power input terminal group of the frequency converter via the normally closed switch of the third main switch of the relay.

[0051] The relay's control coil is connected to any two of the UCH, VCH, and WCH terminals.

[0052] When the high-speed winding terminal block (UCH, VCH, WCH) of the fan in the drying oven controller is energized and the low-speed winding terminal block (UCL, VCL, WCL) of the fan is de-energized, any two phases of the UCH, VCH, and WCH terminals energize the control coil of relay RLY1. The normally open switch of the first main switch of the relay closes, and the normally closed switch of the first main switch of the relay opens. The current flows through the UCH terminal of the high-speed winding terminal block of the fan to the UC terminal of the three-phase power input group of the frequency converter. When the high-speed winding terminal block (UCH, VCH, WCH) of the fan is de-energized and the low-speed winding terminal block (UCL, VCL, WCL) of the fan is energized, the control coil of relay RLY1 is de-energized, the normally open switch of the first main switch of the relay opens, and the normally closed switch of the first main switch of the relay closes. The current flows through the UCL terminal of the low-speed winding terminal block of the fan to the UC terminal of the three-phase power input group of the frequency converter. The second and third main switches operate on the same principle as the first main switch, and will not be described again. When the high-speed winding terminal blocks (UCH, VCH, WCH) of the fan are energized, they supply power to the three-phase power input terminals (UC, VC, WC) of the frequency converter. When the low-speed winding terminal blocks (UCL, VCL, WCL) of the fan are energized, they supply power to the three-phase power input terminals (UC, VC, WC) of the frequency converter. When UCH, VCH, WCH and UCL, VCL, WCL are all de-energized, the frequency converter is de-energized, and the circulating fan stops.

[0053] In addition to the relay control circuit mentioned above, the power switching circuit can also use a microcontroller. The microcontroller detects the voltage of the high-speed winding terminal block and the low-speed winding terminal block of the fan through a sampling circuit. When there is voltage in one of the terminals, the three-phase power input terminals of the frequency converter are connected to the high-speed winding terminal block or the low-speed winding terminal block of the fan with voltage through a contactor. The circuit diagram is omitted.

[0054] like Figure 4 As shown in (b), one end of the normally closed switch of the fourth main switch of relay RLY1 is connected to a DC power supply (+24V), and the other end of the normally closed switch of the fourth main switch is connected to the manual control terminal TIN of the frequency converter; the normally open switch of the fourth main switch of the relay is left floating.

[0055] When manual control is used (manual control is performed by the oven controller, and the control signal from the configuration panel is invalid), the normally closed switch of the fourth main switch detects whether the high-speed winding terminal block (UCH, VCH, WCH) or the low-speed winding terminal block (UCL, VCL, WCL) of the fan is energized. This triggers a DC power signal (e.g., 24V) to the inverter via the manual control terminal TIN. For example, when the low-speed winding terminal block (UCL, VCL, WCL) is energized, the manual control terminal TIN outputs a 24V DC power signal to the inverter, which then controls the circulating fan to run at low speed. Conversely, when there is no DC power signal at the manual control terminal TIN, the inverter controls the circulating fan to run at high speed.

[0056] like Figure 8 As shown, it also includes a power conversion circuit. The two input terminals of the power conversion circuit are connected to the UC terminal and the VC terminal respectively. The output terminal of the power conversion circuit is connected to one end of the normally closed switch of the fourth main switch of the relay RLY1 to provide the DC power supply (+24V). The power conversion circuit also supplies power to the configuration panel and the multi-purpose baking oven temperature sensor.

[0057] like Figure 9 As shown, the frequency converter is also connected to an alarm via the control terminal TB. When the configuration panel detects a fault, such as a temperature sensor fault, the configuration panel controls the alarm to send an alarm signal through the frequency converter.

[0058] 2. Operating Mode. The operating method of the drying oven controller remains unchanged, meaning it is compatible with the operating habits of conventional drying oven controllers.

[0059] During the baking process in a drying oven, the fan speed is generally determined by the oven temperature. Typically, below 42 degrees Celsius, it operates at low speed (960 rpm); between 42 and 54 degrees Celsius, it operates at high speed (1440 rpm); and above 54 degrees Celsius, it operates at low speed (960 rpm). Conventional drying oven controllers require manual monitoring of the oven temperature and manual switching between high and low speed settings for the circulating fan. For drying ovens equipped with frequency converters, the oven controller reads the dry and wet bulb temperatures and sends speed adjustment commands to the frequency converter.

[0060] The wind turbine operation mode of this invention can be set and viewed through a configuration screen.

[0061] Operating modes include: manual mode, multi-gear mode, and forward / reverse mode.

[0062] Manual mode refers to the same fan control method as a conventional drying oven controller. The operator manually operates the circulating fan speed switch on the drying oven controller. The fan controller determines whether to use high or low speed based on the power supply to the fan terminals, and then adjusts the circulating fan speed accordingly via the frequency converter. Generally, high speed is 1440 rpm, and low speed is 960 rpm. The drying operator typically switches the circulating fan speed based on the drying oven temperature: generally, low speed (960 rpm) is used below 42 degrees Celsius, high speed (1440 rpm) is used between 42 and 54 degrees Celsius, and low speed (960 rpm) is used above 54 degrees Celsius.

[0063] Furthermore, the multi-speed mode allows for setting multiple speed settings for the circulating fan. Compared to conventional oven controllers that only offer high and low speed settings, the multi-speed mode provides more flexible speed adjustments based on the oven temperature. For example, the oven baking process typically involves multiple baking stages, each with a different temperature, which can be configured with different fan speeds. See Table 1 below for examples.

[0064] Table 1

[0065] Baking stage Curing oven temperature range (degrees) Fan speed (rpm) 1 ≤35 1200 2 35＜t≤38 960 3 38＜t≤40 960 4 40＜t≤42 960 5 42＜t≤44 1440 6 44＜t≤48 1440 7 48＜t≤54 1200 8 54＜t≤60 1000 9 60＜t≤67 720 10 ≥67 720

[0066] The forward and reverse rotation mode involves setting the fan speed to multiple levels, then separately setting the forward and reverse rotation speeds, and adjusting the cycles for both forward and reverse rotation. See Table 2 below for example.

[0067] Table 2

[0068]

[0069] The fan controller in this application does not need to receive speed adjustment commands from the drying oven controller. The configuration screen reads the temperature of the multi-purpose drying oven temperature sensor as the basis for fan speed adjustment. Different speeds can be set for multiple stages, such as 1200 rpm for temperatures below 36 degrees Celsius, 960 rpm for temperatures between 36 and 42 degrees Celsius, 1440 rpm for temperatures between 42 and 54 degrees Celsius, and 720 rpm for temperatures above 54 degrees Celsius.

[0070] The oven controller does not need to communicate with the fan controller. The fan controller determines the fan speed switch status by detecting the power supply status of the high-speed and low-speed terminals of the oven controller's fan wiring terminals, and adjusts the fan speed to high or low speed via the frequency converter.

[0071] See implementation details Figures 4-9 The high-speed and low-speed winding terminals of the drying oven controller are both connected to the fan controller. The fan controller has a power supply switching circuit (a contactor controlled by the high-speed winding terminal, with normally closed contacts connected to the low-speed winding terminal and normally open contacts connected to the high-speed winding terminal).

[0072] The power supply mode is automatically switched according to the status of the circulating fan speed switch, which can be divided into three cases:

[0073] 1) Stop position. Both the high-speed and low-speed windings are de-energized, so no voltage is transmitted to the fan controller. The fan controller is in a de-energized state, and the circulating fan is also in a de-energized state.

[0074] 2) High-speed mode. The high-speed winding terminal of the oven controller is powered, the low-speed winding terminal is disconnected, and the fan controller draws power from the high-speed winding terminal.

[0075] 3) Low speed mode. The high-speed winding terminal of the oven controller is de-energized, and the low-speed winding terminal is powered. The fan controller draws power from the low-speed winding terminal.

[0076] 3. Multi-purpose curing oven temperature sensor. Used to determine the temperature difference inside the curing oven, serving as a basis for automatically adjusting the speed and direction of the circulating fan.

[0077] Traditional drying ovens are equipped with two sets of sensors: one for the dry-bulb and wet-bulb temperatures of the upper rack and the other for the dry-bulb and wet-bulb temperatures of the lower rack, for a total of four temperature sensors, which are connected to the drying oven controller.

[0078] In this application, the fan controller does not communicate with the drying oven controller; instead, a single multi-purpose drying oven temperature sensor is used to achieve the following functions:

[0079] 1) Measure the temperature difference inside the drying room.

[0080] Because the airflow direction in a conventional tobacco curing barn is fixed, and the loading chamber has an air inlet and an air outlet, hot air enters through the air inlet and exits through the air outlet. Therefore, the temperature is higher near the air inlet and lower near the air outlet. To monitor the temperature difference inside the curing barn, upper and lower temperature sensors need to be installed.

[0081] The multi-purpose drying oven temperature sensor described in this device can be installed on either the upper or lower shelf. A frequency converter is used to time the forward and reverse rotation of the fan, changing the airflow direction and thus swapping the functions of the air inlet and outlet. The original air inlet becomes the actual air outlet, and the original air outlet becomes the actual air inlet, thereby changing the positions of the high-temperature and low-temperature zones. By placing a single multi-purpose drying oven temperature sensor in a fixed location (e.g., the lower shelf), the high and low temperatures of the drying oven can be measured at different times. Figure 10 This is a flowchart of the temperature difference measurement process for the configuration panel. The configuration panel measures the temperature of the high-temperature zone and the low-temperature zone inside the intensive drying oven via a multi-purpose drying oven temperature sensor.

[0082] 2) As a basis for adjusting the fan speed.

[0083] During the baking process in a drying oven, the speed of the circulating fan is generally determined by the oven temperature. Conventional drying oven controllers require manual monitoring of the oven temperature and switching between high and low speed settings. To simplify manual operation, only a simple switching logic is set: typically low speed (960 rpm) below 42 degrees Celsius, high speed (1440 rpm) between 42 and 54 degrees Celsius, and low speed (960 rpm) above 54 degrees Celsius. For drying ovens equipped with frequency converters, the oven controller reads the dry and wet bulb temperatures and sends speed adjustment commands to the frequency converter.

[0084] The fan controller in this application does not need to receive speed adjustment commands from the controller. The configuration screen reads the temperature from the multi-purpose drying oven temperature sensor as the basis for fan speed adjustment, and multiple different speeds can be set. See the multi-speed mode above. For example, typically 1200 rpm below 36 degrees Celsius, 960 rpm below 36-42 degrees Celsius, 1440 rpm in the range of 42-54 degrees Celsius, and 720 rpm above 54 degrees Celsius. Figure 11 As shown, this is the process of adjusting the fan speed in the configuration panel. The configuration panel calls the temperature difference measurement program to adjust the fan speed according to the temperature of the high-temperature zone of the drying oven.

[0085] 3) As a basis for switching the forward and reverse rotation of the circulating fan.

[0086] The rotation direction of the circulating fan in a conventional curing barn is fixed, resulting in high-temperature and low-temperature zones inside the barn. This affects the consistency of the curing quality of tobacco leaves in different areas of the barn. Therefore, by regularly switching the forward and reverse rotation of the circulating fan in the curing barn according to a certain logic, the temperature of tobacco leaves in different areas can be alternately at high and low temperatures, which helps to improve the consistency of curing quality.

[0087] During the curing process in the tobacco curing barn, not only temperature but also humidity are controlled. However, the fan controller described in this device is only connected to one multi-purpose curing barn temperature sensor. To effectively combine the characteristics of the tobacco curing process during forward and reverse rotation control, a special forward and reverse rotation switching method is adopted. See the forward and reverse rotation mode above. Figure 12 The diagram shows the forward and reverse rotation switching process of the circulating fan; the configuration panel controls the forward and reverse rotation of the circulating fan based on the temperature signal from the multi-purpose drying oven temperature sensor using the forward and reverse rotation switching process.

[0088] Advantages of the present invention

[0089] 1) No need to modify the existing curing oven controller or use a dedicated curing oven controller. The fan controller does not need to communicate with the curing oven controller. It includes manual mode, multi-speed mode and forward and reverse mode, which can realize more flexible circulating fan control logic.

[0090] 2) The fan controller is connected to a multi-purpose oven temperature sensor to realize multiple functions of one temperature sensor. It can measure the high and low temperature difference of the oven and also serve as the basis for controlling the speed and direction of the circulating fan.

[0091] 3) A forward and reverse rotation control method was proposed, and the rotation speed and time for forward and reverse rotation were set independently, which is more in line with the requirements of tobacco curing process.

Claims

1. A control device for the circulating fan of a high-density drying room, comprising a frequency converter and a configuration panel, characterized in that, It also includes a power switching circuit. The three-phase power input terminal group of the frequency converter is connected to the high-speed winding terminal block and the low-speed winding terminal block of the fan of the drying oven controller via the power switching circuit. The high-speed winding terminal block and the low-speed winding terminal block of the fan of the drying oven controller supply power to the frequency converter. The automatic control terminal group of the frequency converter is connected to a configuration panel, which is connected to a multi-purpose drying oven temperature sensor. The three-phase power output terminal group of the frequency converter is connected to the high-speed winding terminal block of the circulating fan, and the low-speed winding terminal block of the circulating fan is short-circuited. The configuration panel controls the operation of the circulating fan through the frequency converter based on the signal from the multi-purpose drying oven temperature sensor.

2. The intensive drying oven circulating fan control device according to claim 1, characterized in that: The power switching circuit includes relays; The UCH terminal of the high-speed winding terminal block of the fan is connected to the UC terminal of the three-phase power input terminal group of the frequency converter via the normally open switch of the first main switch of the relay. The UCL terminal of the low-speed winding terminal block of the fan is connected to the UC terminal of the three-phase power input terminal group of the frequency converter via the normally closed switch of the first main switch of the relay. The VCH terminal of the high-speed winding terminal block of the fan is connected to the VC terminal of the three-phase power input terminal group of the frequency converter via the normally open switch of the second main switch of the relay. The VCL terminal of the low-speed winding terminal block of the fan is connected to the VC terminal of the three-phase power input terminal group of the frequency converter via the normally closed switch of the second main switch of the relay. The WCH terminal of the high-speed winding terminal block of the fan is connected to the WC terminal of the three-phase power input terminal group of the frequency converter via the normally open switch of the third main switch of the relay. The WCL terminal of the low-speed winding terminal block of the fan is connected to the WC terminal of the three-phase power input terminal group of the frequency converter via the normally closed switch of the third main switch of the relay. The relay's control coil is connected to any two of the UCH, VCH, and WCH terminals.

3. The intensive drying oven circulating fan control device according to claim 2, characterized in that: One end of the normally closed switch of the fourth main switch of the relay is connected to a DC power supply, and the other end of the normally closed switch of the fourth main switch is connected to the manual control terminal TIN of the frequency converter.

4. The intensive drying oven circulating fan control device according to claim 3, characterized in that: It also includes a power conversion circuit, whose two input terminals are connected to the UC terminal and the VC terminal respectively, and whose output terminal is connected to one end of the normally closed switch of the fourth main switch to provide the DC power. The power conversion circuit also supplies power to the configuration panel and the multi-purpose oven temperature sensor.

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