Control circuit for cooperative use of frequency converter and cooling fan

Abstract

The utility model discloses a control circuit for cooperative use of a frequency converter and a cooling fan. The control circuit comprises a main loop and a control loop. The main loop comprises a main switch QF1, a frequency converter and a variable frequency motor which are sequentially connected in series on a three-phase power line; the control loop comprises a normally open contact of a first intermediate relay KA1, a normally open contact of a contactor KM of a cooling fan, a normally open contact of a second intermediate relay KA2, a first branch, a second branch and a third branch, wherein the first branch, the second branch and the third branch are connected in parallel. The two ends of the stop button SB1 in the first branch are connected in parallel with a normally open contact of a first intermediate relay KA1, and the two ends of the start button SB2 in the first branch are connected in parallel with a normally open contact of a contactor KM of a cooling fan; the two ends of the normally open contact of the stop button SB1 in the second branch are connected in parallel with the normally open contact of a second intermediate relay KA2; and the third branch is formed by connecting a contact K of the PLC and a coil of the first intermediate relay KA1 in series.

Description

Technical field:

[0001] The utility model relates to the technical field of motor cooling, in particular to a control circuit used in conjunction with a frequency converter and a cooling fan. Background technology:

[0002] Variable frequency motors are generally powered by frequency converters, and the motor speed is variable. In the hot summer, especially in Xinjiang, the ambient temperature is high. Due to the small air volume of the frequency converter's built-in cooling fan and the limited space in the electrical control box, the heat dissipation effect of the built-in cooling fan is not ideal.

[0003] At present, independent fans are often used on the market to cool down the frequency converter. However, due to operating errors of operators, they often forget to start the cooling fan after starting the frequency converter motor, or stop the cooling fan before stopping the frequency converter. This results in the frequency converter not dissipating heat in time and insufficient cooling, often causing high temperature alarm and shutdown, or even burning of the frequency converter motor, which seriously affects production. Utility model content:

[0004] The utility model aims to provide a control circuit for use with a frequency converter and a cooling fan.

[0005] The purpose of the utility model is implemented by the following technical solution: a control circuit used in conjunction with a frequency converter and a cooling fan, which includes a main circuit and a control circuit;

[0006] The main circuit includes a main switch QF1, a frequency converter and a variable frequency motor connected in series on the three-phase power line in sequence; the normally closed contact of the second intermediate relay KA2, the normally open contact of the contactor KM of the cooling fan and the normally open contact of the first intermediate relay KA1 are connected in series between the a terminal and the c terminal of the frequency converter, and the a terminal and the b terminal of the frequency converter are short-circuited;

[0007] The control loop includes a normally open contact of a first intermediate relay KA1, a normally open contact of a contactor KM of a cooling fan, a normally open contact of a second intermediate relay KA2, a first branch, a second branch and a third branch; the first branch, the second branch and the third branch are connected in parallel;

[0008] The first branch is composed of a normally closed contact of a stop button SB1, a normally open contact of a start button SB2, and a contactor KM coil of a cooling fan connected in series. The two ends of the normally closed contact of the stop button SB1 in the first branch are connected in parallel with the normally open contacts of the first intermediate relay KA1, and the two ends of the normally open contact of the start button SB2 in the first branch are connected in parallel with the normally open contacts of the contactor KM of the cooling fan;

[0009] The second branch circuit is composed of the normally open contact of the stop button SB1, the normally closed contact of the start button SB2, and the coil of the second intermediate relay KA2 connected in series. The normally open contact of the second intermediate relay KA2 is connected in parallel at both ends of the normally open contact of the stop button SB1 in the second branch circuit;

[0010] The third branch circuit is composed of the contact K of the PLC controller and the coil of the first intermediate relay KA1 connected in series.

[0011] Preferably, the control loop further includes a control switch QF2. After the first branch circuit, the second branch circuit, and the third branch circuit are connected in parallel, they are then connected in series with the control switch QF2 to form a closed loop.

[0012] Advantages of the present utility model: Through the present utility model, it is possible to achieve the purpose that the cooling fan starts and runs earlier than the frequency converter, and the cooling fan stops running later than the frequency converter. Even if the operator makes a wrong operation and first connects the contact K of the PLC controller, the frequency converter cannot be directly started. After pressing the start button SB2 and starting the cooling fan to run, the frequency converter can be started; or, in case of a wrong operation - first pressing the stop button SB1, the cooling fan cannot be directly stopped. It is necessary to first disconnect the contact K of the PLC controller to make the normally open contact of the first intermediate relay KA1 in the main circuit disconnect. After the frequency converter stops running, then press the stop button SB1 again to stop the cooling fan. Description of the drawings:

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative labor, other drawings can be obtained based on these drawings.

[0014] Figure 1 It is a circuit schematic diagram of the main circuit in the present utility model.

[0015] Figure 2 It is a circuit schematic diagram of the control loop in the present utility model.

[0016] The marks of each component in the drawings are as follows: main switch QF1, control switch QF2, first branch circuit 1, second branch circuit 2, third branch circuit 3, stop button SB1, start button SB2, contactor KM of the cooling fan, first intermediate relay KA1, second intermediate relay KA2, contact K of the PLC controller, variable frequency motor M, frequency converter 4. Specific implementation manners:

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present utility model in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without making creative efforts belong to the scope of protection of the present utility model.

[0018] As Figure 1 - Figure 2 shown, a control circuit for the coordinated use of an inverter and a cooling fan includes a main circuit and a control circuit; among them, in the main circuit, when the a terminal and the c terminal of the inverter 4 are connected, the inverter 4 starts, causing the variable-frequency motor M to operate;

[0019] The main circuit includes a variable-frequency motor M, an inverter 4, a main switch QF1, a normally open contact of the contactor KM of the cooling fan, a normally open contact of the first intermediate relay KA1, and a normally closed contact of the second intermediate relay KA2;

[0020] The main switch QF1, the inverter 4, and the variable-frequency motor M are sequentially connected in series on the three-phase power line; between the a terminal and the c terminal of the inverter 4, a normally closed contact of the second intermediate relay KA2, a normally open contact of the contactor KM of the cooling fan, and a normally open contact of the first intermediate relay KA1 are connected in series, and the a terminal and the b terminal of the inverter 4 are short-circuited; when the a terminal and the c terminal are connected, the inverter 4 starts to operate; when the a terminal and the c terminal are disconnected, the inverter 4 stops operating;

[0021] The control circuit includes a control switch QF2, a first branch 1, a normally open contact of the first intermediate relay KA1, a normally open contact of the contactor KM of the cooling fan, a second branch 2, a normally open contact of the second intermediate relay KA2, and a third branch 3;

[0022] The first branch 1 is composed of a normally closed contact of the stop button SB1, a normally open contact of the start button SB2, and the coil of the contactor KM of the cooling fan connected in series in sequence. By the energization and de-energization of the coil of the contactor KM of the cooling fan in the first branch 1, the start and stop operations of the cooling fan are controlled; a normally open contact of the first intermediate relay KA1 is connected in parallel at both ends of the normally closed contact of the stop button SB1 in the first branch 1, and a normally open contact of the contactor KM of the cooling fan is connected in parallel at both ends of the normally open contact of the start button SB2 in the first branch 1;

[0023] The second branch 2 is composed of a normally open contact of the stop button SB1, a normally closed contact of the start button SB2, and the coil of the second intermediate relay KA2 connected in series in sequence. A normally open contact of the second intermediate relay KA2 is connected in parallel at both ends of the normally open contact of the stop button SB1 in the second branch 2;

[0024] The third branch 3 is composed of the contact K of the PLC controller and the coil of the first intermediate relay KA1 connected in series. By closing or opening the contact K of the PLC controller, the coil of the first intermediate relay KA1 is energized or de-energized, controlling the normally open contact of the first intermediate relay KA1 in the main circuit to close or open, thereby controlling the start and stop of the frequency converter 4;

[0025] After the first branch 1, the second branch 2, and the third branch 3 are connected in parallel, they are then connected in series with the control switch QF2 to form a closed loop.

[0026] Working process: To ensure that the variable-frequency motor M and the frequency converter 4 are always in a cooled state during operation, the requirements are as follows: The cooling fan should start running before the frequency converter 4, and the cooling fan can only stop running after the frequency converter 4 stops running. The specific process is as follows:

[0027] First, close the main switch QF1 and the control switch QF2, and press the start button SB2. The coil of the contactor KM of the cooling fan is instantaneously energized and attracted, driving the normally open contact of the contactor KM of the cooling fan to close, forming self-locking, and the cooling fan starts running;

[0028] Secondly, connect the contact K of the PLC controller. The coil of the first intermediate relay KA1 is energized, the normally open contact of the first intermediate relay KA1 in the main circuit closes, and the frequency converter 4 starts; and the normally open contact of the first intermediate relay KA1 in the first branch 1 closes;

[0029] Then, disconnect the contact K of the PLC controller. The coil of the first intermediate relay KA1 is de-energized, and the already closed normally open contact of the first intermediate relay KA1 in the main circuit opens, and the frequency converter 4 stops running;

[0030] Finally, press the stop button SB1. The coil of the contactor KM of the cooling fan in the first branch 1 is de-energized, and the cooling fan stops running;

[0031] If, during the operation of the cooling fan, the operator forgets to first disconnect the contact point K of the PLC controller to stop the operation of the frequency converter 4; instead, the operator directly presses the stop button SB1. Since the third branch 3 is always in the closed state, that is, the coil of the first intermediate relay KA1 is energized. At this time, the normally open contact of the first intermediate relay KA1 in the first branch 1 is in the closed state. Even if the stop button SB1 is directly pressed, the coil of the contactor KM of the cooling fan is still energized and maintains the self-locking state, and the cooling fan will not stop running; while the normally open contact of the stop button SB1 in the second branch 2 is instantaneously closed, the coil of the second intermediate relay KA2 is instantaneously energized and the normally open contact of the second intermediate relay KA2 is closed to form self-locking. At this time, the normally closed contact of the second intermediate relay KA2 in the main circuit is disconnected, and the frequency converter 4 stops running; it is necessary to disconnect the contact point K of the PLC controller again to de-energize the coil of the first intermediate relay KA1, and the normally open contact of the first intermediate relay KA1 that has been closed in the first branch 1 is in the open state, the coil of the contactor KM of the cooling fan is de-energized, and the cooling fan stops running;

[0032] When it is necessary to restart the frequency converter 4 to make the frequency conversion motor M run, if the operator forgets to first press the start button SB2 to start the cooling fan first, instead, after directly closing the contact point K of the PLC controller in the third branch 3, the coil of the first intermediate relay KA1 is energized, and the normally open contact of the first intermediate relay KA1 in the main circuit is closed. Since the coil of the second intermediate relay KA2 is still energized and maintains the self-locking state, the normally closed contact of the second intermediate relay KA2 in the main circuit is always in the open state, and the frequency converter 4 will not start running; it is necessary for the operator to press the start button SB2 again. The normally closed contact of the start button SB2 in the second branch 2 is disconnected, the coil of the second intermediate relay KA2 is de-energized, and the normally closed contact of the second intermediate relay KA2 that has been disconnected in the main circuit is closed. At the same time, the coil of the contactor KM of the cooling fan is instantaneously energized and the normally open contact of the contactor KM of the cooling fan is closed to form self-locking, the cooling fan starts running, and the normally open contact of the first intermediate relay KA1 in the main circuit is closed, and the frequency converter 4 starts;

[0033] Therefore, through the above circuit, the purpose of making the cooling fan start running earlier than the frequency converter 4 and stop running later than the frequency converter 4 can be achieved. Even if the operator makes an operation error and first closes the contact point K of the PLC controller, the frequency converter 4 cannot be directly started. It is necessary to press the start button SB2 again, and after starting the cooling fan to run, the frequency converter 4 can be started; or, due to misoperation - first pressing the stop button SB1, the cooling fan cannot be directly stopped, and the frequency converter 4 will stop running first. It is necessary to disconnect the contact point K of the PLC controller again to stop the cooling fan from running.

[0034] The above are only the preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A control circuit for the coordinated use of a frequency converter and a cooling fan, characterized in that, It includes a main circuit and a control circuit; The main circuit includes a main switch QF1, an inverter, and a variable-frequency motor connected in series in sequence on the three-phase power line; a normally-closed contact of a second intermediate relay KA2, a normally-open contact of a contactor KM of a cooling fan, and a normally-open contact of a first intermediate relay KA1 are connected in series between the a terminal and the c terminal of the inverter, and the a terminal and the b terminal of the inverter are short-circuited; The control circuit includes a normally-open contact of a first intermediate relay KA1, a normally-open contact of a contactor KM of a cooling fan, a normally-open contact of a second intermediate relay KA2, a first branch, a second branch, and a third branch; the first branch, the second branch, and the third branch are connected in parallel; The first branch is composed of a normally-closed contact of a stop button SB1, a normally-open contact of a start button SB2, and a coil of a contactor KM of a cooling fan connected in series. A normally-open contact of a first intermediate relay KA1 is connected in parallel at both ends of the normally-closed contact of the stop button SB1 in the first branch, and a normally-open contact of the contactor KM of the cooling fan is connected in parallel at both ends of the normally-open contact of the start button SB2 in the first branch; The second branch is composed of a normally-open contact of a stop button SB1, a normally-closed contact of a start button SB2, and a coil of a second intermediate relay KA2 connected in series. A normally-open contact of a second intermediate relay KA2 is connected in parallel at both ends of the normally-open contact of the stop button SB1 in the second branch; The third branch is composed of a contact K of a PLC controller and a coil of a first intermediate relay KA1 connected in series.

2. The control circuit for the combined use of an inverter and a cooling fan according to claim 1, wherein A control switch QF2 is further included in the control circuit. After the first branch, the second branch, and the third branch are connected in parallel, they are then connected in series with the control switch QF2 to form a closed loop.

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