An improved circuit for variable frequency motor

Abstract

This invention relates to an improved circuit for variable frequency motors, a start-stop control circuit, and a current monitoring module. The current monitoring module monitors the current in the output circuit of the variable frequency drive. The start-stop control circuit, driven by a control component, continuously outputs a fan control signal to the current monitoring module. The current monitoring module, in response to the fan control signal output by the start-stop control circuit, stops outputting a first control signal to the cooling fan control port of the variable frequency drive to shut down the cooling fan when the current monitored by the current monitoring module is less than or equal to a preset threshold; or outputs a second control signal to the cooling fan control port of the variable frequency drive to start the cooling fan when the current monitored by the current monitoring module is greater than the preset threshold. This invention significantly improves the service life of the cooling fan of the variable frequency motor and effectively saves energy.

Description

Technical Field

[0001] This invention relates to the field of variable frequency motors, and in particular to an improved circuit for variable frequency motors. Background Technology

[0002] Because the control of variable frequency motors originates from a distributed control system (DCS) or a programmable logic controller (PLC), operators need to continuously adjust the motor speed to meet different process requirements. Existing control circuits often control both the inverter's starting relay and the main unit's cooling fan. However, in practice, for convenience, operators often only adjust the main unit's setpoint to "0" when stopping the machine, without disconnecting the starting relay. This results in the cooling fan continuing to run even when the variable frequency motor is stopped. Prolonged operation of the cooling fan leads to frequent failures and a short lifespan. Summary of the Invention

[0003] In view of this, the present invention aims to provide an improved circuit for variable frequency motors that stops the cooling fan when the motor speed is 0 or lower, in order to solve the problems mentioned in the prior art.

[0004] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0005] The first aspect of the present invention provides an improved circuit for a variable frequency motor, comprising:

[0006] Start-stop control circuit and current monitoring module;

[0007] The current monitoring module is used to monitor the current in the output circuit of the frequency converter;

[0008] The start-stop control circuit is driven by the control component to continuously output fan control signals to the current monitoring module;

[0009] The current monitoring module also responds to the fan control signal output by the start / stop control circuit by stopping the output of a first control signal to the inverter's cooling fan control port to shut down the cooling fan when the current monitored by the current monitoring module is less than or equal to a preset threshold; or by outputting a second control signal to the inverter's cooling fan control port to turn on the cooling fan when the current monitored by the current monitoring module is greater than the preset threshold.

[0010] Furthermore, the control component is a DCS control component or a PLC control component.

[0011] Furthermore, the current monitoring module is one of an ammeter with relay output function, an energy meter with relay output function, and a current transmitter with relay output function.

[0012] Furthermore, the current monitoring module includes a current monitoring module and a relay output module;

[0013] The current monitoring module is used to monitor the current in the output circuit of the frequency converter;

[0014] The relay output module, in response to the fan control signal output by the start / stop control circuit, stops outputting a first control signal to the inverter's cooling fan control port to shut down the cooling fan when the current monitored by the current monitoring module is less than or equal to a preset threshold; or, outputs a second control signal to the inverter's cooling fan control port to turn on the cooling fan when the current monitored by the current monitoring module is greater than the preset threshold.

[0015] Furthermore, the start-stop control circuit includes a first power supply, a first intermediate relay, a second intermediate relay, and a contactor;

[0016] The first terminal of the first power supply is connected to one end of the start control contact and one end of the stop control contact of the control module, respectively; the other end of the start control contact of the control module is connected to one end of the coil of the first intermediate relay; the other end of the coil of the first intermediate relay is connected to the second terminal of the first power supply; the other end of the stop control contact of the control module is connected to one end of the coil of the second intermediate relay; the other end of the coil of the second intermediate relay is connected to the second terminal of the first power supply.

[0017] The first terminal of the first power supply is connected to one end of the normally closed auxiliary contact of the second intermediate relay. The other end of the normally closed auxiliary contact of the second intermediate relay is connected to one end of the normally open auxiliary contact of the first intermediate relay and one end of the first normally open auxiliary contact of the contactor, respectively. The other end of the normally open auxiliary contact of the first intermediate relay and the other end of the first normally open auxiliary contact of the contactor are connected to one end of the relay output module. The other end of the relay output module is connected to the second terminal of the first power supply.

[0018] One end of the second normally open contact of the contactor is connected to one end of the cooling fan control port of the frequency converter, and the other end of the second normally open contact of the contactor is connected to the other end of the cooling fan control port of the frequency converter.

[0019] Furthermore, the start / stop control circuit also includes a third intermediate relay;

[0020] The first end of the first power supply is connected to one end of the fault feedback contact of the frequency converter; the other end of the fault feedback contact of the frequency converter is connected to one end of the coil of the third intermediate relay, and the other end of the coil of the third intermediate relay is connected to the second end of the first power supply.

[0021] One end of the normally closed auxiliary contact of the third intermediate relay is connected to the other end of the normally open auxiliary contact of the first intermediate relay and the other end of the first normally open auxiliary contact of the contactor, and the other end of the normally closed auxiliary contact of the third intermediate relay is connected to one end of the relay output module.

[0022] Furthermore, the start-stop control circuit also includes a fault indicator light, which is connected in parallel across the coil of the third intermediate relay.

[0023] Furthermore, the control circuit also includes a fuse; the first end of the first power supply is connected to one end of the fuse, and the other end of the fuse is connected to one end of the control module start control contact, one end of the stop control contact, and one end of the normally closed auxiliary contact of the second intermediate relay.

[0024] Furthermore, the output circuit of the frequency converter includes a second power supply, a circuit breaker, the frequency converter, and a motor;

[0025] The first end of the second power supply is connected to one end of the circuit breaker, the other end of the circuit breaker is connected to one end of the current monitoring module, the other end of the current monitoring module is connected to the input end of the main circuit of the frequency converter, the output end of the main circuit of the frequency converter is connected to one end of the motor, and the other end of the motor is connected to the second end of the second power supply.

[0026] Furthermore, the output circuit of the frequency converter also includes a reactor, one end of which is connected to the other end of the motor, and the other end is connected to the second end of the second power supply.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] In this invention,

[0029] This invention controls the operation of the inverter's cooling fan through a current monitoring module. When the inverter is running, if the operator sets the inverter's setpoint frequency to 0, the current monitored by the current monitoring module is less than or equal to a preset threshold. This disconnects the fan control signal output by the start / stop control circuit, preventing it from being transmitted to the inverter's cooling fan control port, and the cooling fan stops. When the operator sets the inverter's setpoint frequency to the normal frequency, the current monitored by the current monitoring module exceeds the preset threshold, allowing the fan control signal output by the start / stop control circuit to be transmitted to the inverter's cooling fan control port, and the cooling fan resumes operation. This invention significantly improves the service life of the inverter motor's cooling fan and effectively saves energy. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0031] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0032] Figure 2 This is a schematic diagram of the cooling fan control structure of the frequency converter of the present invention;

[0033] Figure 3 This is a schematic diagram of the output circuit of the frequency converter of the present invention. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0035] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "back," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] Furthermore, in the description of this invention, unless otherwise explicitly defined, the terms "installation," "connection," "linking," and "connector" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention in light of the specific circumstances.

[0037] The following will refer to the appendix. Figures 1 to 3 The present invention will be described in detail with reference to the embodiments.

[0038] Overall, this invention provides an improved circuit for variable frequency motors, comprising:

[0039] Start-stop control circuit and current monitoring module TA1;

[0040] The current monitoring module TA1 is used to monitor the current in the output circuit of the inverter VFD.

[0041] The start / stop control circuit is driven by the control components to continuously output fan control signals to the current monitoring module TA1;

[0042] The current monitoring module TA1 also responds to the fan control signal output by the start-stop control circuit. When the current monitored by the current monitoring module TA1 is less than or equal to a preset threshold, it stops outputting a first control signal to the cooling fan control port of the inverter VFD to shut down the cooling fan; or, when the current monitored by the current monitoring module TA1 is greater than the preset threshold, it outputs a second control signal to the cooling fan control port of the inverter VFD to turn on the cooling fan.

[0043] This invention controls the operation of the VFD (Variable Frequency Drive) cooling fan via a current monitoring module TA1. When the VFD is running, if the operator sets the VFD's setpoint frequency to 0, the current monitored by TA1 is less than or equal to a preset threshold. This disconnects the fan control signal output by the start / stop control circuit, preventing it from being transmitted to the VFD's cooling fan control port, and the cooling fan stops. When the operator sets the VFD's setpoint frequency to the normal frequency, the current monitored by TA1 exceeds the preset threshold, allowing the fan control signal output by the start / stop control circuit to be transmitted to the VFD's cooling fan control port, and the cooling fan resumes operation. This invention significantly improves the service life of the variable frequency motor cooling fan and effectively saves energy.

[0044] In a preferred embodiment, the control component is a DCS control component or a PLC control component.

[0045] In a preferred embodiment, the current monitoring module TA1 is one of an ammeter with relay output function, an energy meter with relay output function, and a current transmitter with relay output function.

[0046] In one possible implementation, when the motor operating current is large, the current monitoring module TA1 needs to collect the current in the output circuit of the frequency converter VFD through the current transformer.

[0047] In a preferred embodiment, the current monitoring module TA1 includes a current monitoring module and a relay output module; in this embodiment, the current monitoring module TA1 is preferably a Fearlie F509 AC digital display ammeter, which has the function of setting alarm upper and lower limits. When the current is less than the preset lower limit current or greater than the preset upper limit current, the normally open contact in its internal relay module closes.

[0048] The current monitoring module is used to monitor the current in the output circuit of the inverter VFD.

[0049] The relay output module, in response to the fan control signal output by the start / stop control circuit, stops outputting a first control signal to the cooling fan control port of the inverter VFD to shut down the cooling fan when the current monitored by the current monitoring module is less than or equal to a preset threshold; or, outputs a second control signal to the cooling fan control port of the inverter VFD to turn on the cooling fan when the current monitored by the current monitoring module is greater than the preset threshold.

[0050] In a preferred embodiment, the start-stop control circuit includes a first power supply L1, a first intermediate relay KA1, a second intermediate relay KA2, and a contactor KM;

[0051] The first terminal of the first power supply L1 is connected to one terminal of the control module start control contact K1 and one terminal of the stop control contact K2 respectively; the other terminal of the control module start control contact K1 is connected to one terminal of the coil of the first intermediate relay KA1; the other terminal of the coil of the first intermediate relay KA1 is connected to the second terminal of the first power supply L1; the other terminal of the control module stop control contact K2 is connected to one terminal of the coil of the second intermediate relay KA2; the other terminal of the coil of the second intermediate relay KA2 is connected to the second terminal of the first power supply L1.

[0052] The first terminal of the first power supply L1 is connected to one end of the normally closed auxiliary contact of the second intermediate relay KA2. The other end of the normally closed auxiliary contact of the second intermediate relay KA2 is connected to one end of the normally open auxiliary contact of the first intermediate relay KA1 and one end of the first normally open contact KM-1 of the contactor. The other end of the normally open auxiliary contact of the first intermediate relay KA1 and the other end of the first normally open contact KM-1 of the contactor are connected to one end of the relay output module. The other end of the relay output module is connected to the second terminal of the first power supply L1.

[0053] One end of the second normally open contact KM-2 of the contactor is connected to one end of the cooling fan control port of the VFD, and the other end of the second normally open contact KM-2 of the contactor is connected to the other end of the cooling fan control port of the VFD.

[0054] In a preferred embodiment, the start-stop control circuit further includes a third intermediate relay KA3;

[0055] The first end of the first power supply L1 is connected to one end R1A of the fault feedback contact of the frequency converter VFD; the other end R1C of the fault feedback contact of the frequency converter VFD is connected to one end of the coil of the third intermediate relay KA3, and the other end of the coil of the third intermediate relay KA3 is connected to the second end of the first power supply L1.

[0056] One end of the normally closed auxiliary contact of the third intermediate relay KA3 is connected to the other end of the normally open auxiliary contact of the first intermediate relay KA1 and the other end of the first normally open contact KM-1 of the contactor. The other end of the normally closed auxiliary contact of the third intermediate relay KA3 is connected to one end of the relay output module.

[0057] In a preferred embodiment, the start-stop control circuit further includes a fault indicator light, which is connected in parallel across the coil of the third intermediate relay KA3.

[0058] In a preferred embodiment, the control circuit further includes a fuse FU; the first end of the first power supply L1 is connected to one end of the fuse FU, and the other end of the fuse FU is connected to one end of the control module start control contact K1, one end of the stop control contact K2, and one end of the normally closed auxiliary contact of the second intermediate relay KA2.

[0059] In a preferred embodiment, the output circuit of the frequency converter VFD includes a second power supply L2, a circuit breaker QF1, the frequency converter VFD, and a motor.

[0060] The first terminal of the second power supply L2 is connected to one end of the circuit breaker QF1, the other end of the circuit breaker QF1 is connected to one end of the current monitoring module TA1, the other end of the current monitoring module TA1 is connected to the input terminal of the main circuit of the frequency converter VFD, the output terminal of the main circuit of the frequency converter VFD is connected to one end of the motor, and the other end of the motor is connected to the second terminal of the second power supply L2.

[0061] The output circuit of the frequency converter VFD also includes a reactor. One end of the reactor is connected to the other end of the motor, and the other end is connected to the second end of the second power supply L2.

[0062] like Figure 2 This invention uses the current monitoring module TA1 to perform hardware control on the inverter cooling fan without affecting the alarm function of the host unit overheating or the main circuit cutoff function caused by the cooling fan failure.

[0063] The working principle of this invention is as follows:

[0064] Reference Figure 1 The DCS continuously controls the closing of the drive contact K1, energizing the coil of KA1. This causes the normally open auxiliary contact of KA1 to close, energizing the coil of KM. The first normally open contact of KM then closes, causing the circuit to self-lock. Figure 2 When the second normally open contact of KM engages, the inverter's cooling fan starts. At this time, when the operator sets the inverter's setpoint frequency to 0, the motor does not rotate. Figure 3When TA1 detects that the current is lower than the preset threshold, the normally open contact of TA1 opens. When the operator adjusts the frequency of the inverter to normal, the current detected by TA1 is higher than the preset threshold. At this time, the normally open contact of TA1 closes, the coil of KM is re-energized, and the cooling fan of the inverter restarts.

[0065] When the DCS continuously controlled component drives the contact K2 to close, the coil of KA2 is energized and attracted, and the normally closed auxiliary contact of KA2 opens, at which point the cooling fan is turned off.

[0066] In this embodiment, for ease of connection, the first power supply and the second power supply are the same.

[0067] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An improved circuit for variable frequency motors, characterized in that, include: Start-stop control circuit and current monitoring module; The current monitoring module is used to monitor the current in the output circuit of the frequency converter; The start-stop control circuit is driven by the control component to continuously output fan control signals to the current monitoring module; The current monitoring module also responds to the fan control signal output by the start-stop control circuit, and stops outputting a first control signal to the inverter's cooling fan control port to shut down the cooling fan when the current monitored by the current monitoring module is less than or equal to a preset threshold; or outputs a second control signal to the inverter's cooling fan control port to turn on the cooling fan when the current monitored by the current monitoring module is greater than the preset threshold. The current monitoring module includes a current monitoring module and a relay output module; The current monitoring module is used to monitor the current in the output circuit of the frequency converter; The relay output module, in response to the fan control signal output by the start-stop control circuit, stops outputting a first control signal to the inverter's cooling fan control port to shut down the cooling fan when the current monitored by the current monitoring module is less than or equal to a preset threshold; or, outputs a second control signal to the inverter's cooling fan control port to turn on the cooling fan when the current monitored by the current monitoring module is greater than the preset threshold. The start / stop control circuit includes a first power supply, a first intermediate relay, a second intermediate relay, and a contactor; The first terminal of the first power supply is connected to one end of the start control contact and one end of the stop control contact of the control module, respectively; the other end of the start control contact of the control module is connected to one end of the coil of the first intermediate relay; the other end of the coil of the first intermediate relay is connected to the second terminal of the first power supply; the other end of the stop control contact of the control module is connected to one end of the coil of the second intermediate relay; the other end of the coil of the second intermediate relay is connected to the second terminal of the first power supply. The first terminal of the first power supply is connected to one end of the normally closed auxiliary contact of the second intermediate relay. The other end of the normally closed auxiliary contact of the second intermediate relay is connected to one end of the normally open auxiliary contact of the first intermediate relay and one end of the first normally open auxiliary contact of the contactor, respectively. The other end of the normally open auxiliary contact of the first intermediate relay and the other end of the first normally open auxiliary contact of the contactor are connected to one end of the relay output module. The other end of the relay output module is connected to the second terminal of the first power supply. One end of the second normally open contact of the contactor is connected to one end of the cooling fan control port of the frequency converter, and the other end of the second normally open contact of the contactor is connected to the other end of the cooling fan control port of the frequency converter.

2. The improved circuit for a variable frequency motor according to claim 1, characterized in that: The control component is a DCS control component or a PLC control component.

3. The improved circuit for a variable frequency motor according to claim 1, characterized in that: The current monitoring module is one of the following: an ammeter with relay output function, an energy meter with relay output function, and a current transmitter with relay output function.

4. The improved circuit for a variable frequency motor according to claim 1, characterized in that: The start / stop control circuit also includes a third intermediate relay; The first end of the first power supply is connected to one end of the fault feedback contact of the frequency converter; the other end of the fault feedback contact of the frequency converter is connected to one end of the coil of the third intermediate relay, and the other end of the coil of the third intermediate relay is connected to the second end of the first power supply. One end of the normally closed auxiliary contact of the third intermediate relay is connected to the other end of the normally open auxiliary contact of the first intermediate relay and the other end of the first normally open auxiliary contact of the contactor, and the other end of the normally closed auxiliary contact of the third intermediate relay is connected to one end of the relay output module.

5. The improved circuit for a variable frequency motor according to claim 4, characterized in that: The start / stop control circuit also includes a fault indicator light, which is connected in parallel across the coil of the third intermediate relay.

6. The improved circuit for a variable frequency motor according to claim 1, characterized in that: The start / stop control circuit also includes a fuse; the first end of the first power supply is connected to one end of the fuse, and the other end of the fuse is connected to one end of the start control contact of the control module, one end of the stop control contact, and one end of the normally closed auxiliary contact of the second intermediate relay.

7. The improved circuit for a variable frequency motor according to claim 1, characterized in that: The output circuit of the frequency converter includes a second power supply, a circuit breaker, the frequency converter, and a motor. The first end of the second power supply is connected to one end of the circuit breaker, the other end of the circuit breaker is connected to one end of the current monitoring module, the other end of the current monitoring module is connected to the input end of the main circuit of the frequency converter, the output end of the main circuit of the frequency converter is connected to one end of the motor, and the other end of the motor is connected to the second end of the second power supply.

8. The improved circuit for a variable frequency motor according to claim 1, characterized in that: The output circuit of the frequency converter also includes a reactor, one end of which is connected to the other end of the motor, and the other end is connected to the second end of the second power supply.

Images