Logic design method of motor temperature protection in control system

Abstract

The invention discloses a logic design method for motor temperature protection in a control system, which is characterized by comprising the following steps of: judging the change rate of an output value signal in an input module by adding a rate calculation module, and sending a rate over-limit signal when the change rate exceeds a set value; and the logic calculation module performs logic operation on the bad value signal, the over-high protection value signal and the rate over-limit signal so as to realize protection output and alarm output. After the motor temperature protection logic method is adopted, any instrument equipment does not need to be added, and configuration can be conveniently realized in a control system. Practice proves that the method is simple and applicable, not only can the production device and personal safety be protected to the greatest extent, but also mistaken motor temperature protection action can be avoided to the greatest extent, and mistaken shutdown under abnormal conditions can be reduced as much as possible.

Description

Technical Field

[0001] The invention relates to the field of motors, and in particular to a logic design method for motor temperature protection in a control system. Background Art

[0002] For high-power motors, when the temperature of the motor bearings and stators is too high, in order to protect the motor equipment, a protective action will be triggered, that is, the motor will be stopped, thereby stopping the motor-driven equipment (fans, pumps, etc.), which may eventually lead to the shutdown of the entire production system. The safety interlock design not only requires maximum protection of production equipment and personal safety, but also requires minimizing false stops under abnormal conditions. In the actual production process, Pt00 thermal resistors are usually used as temperature measuring elements for motor bearings and stators. Due to broken wires in the temperature measuring elements or poor contact or loose terminal wiring, the measured temperature will suddenly rise, which may cause a protective action. This is a false action, and frequent false actions will seriously affect the normal operation of production. When implementing protection logic design in a control system, our usual logic design is as follows: Figure 1 shown.

[0003] The "input module" processes the signal sent by the "temperature measuring element", such as range definition, over-high protection value setting, signal bad value judgment, etc., and then performs logical operations to AND the "bad value" with the "over-high protection value". That is, when the temperature measuring element is normal and the temperature exceeds the "over-high protection value", the output protection action is taken.

[0004] Here, it only relies on the "bad value" judgment of the "input module" in the control system. Practice has proved that this logic design has certain defects and occasionally causes false protection actions. In the actual production process, since the motor temperature measuring element (RTD) will have a delay when it is disconnected, it will not break immediately. In addition, when the terminal is in poor contact or loose, the temperature value will fluctuate, which will cause false protection actions and seriously affect the normal operation of production. Summary of the invention

[0005] The purpose of the present invention is to provide a logic design method for motor temperature protection in a control system. The present invention does not require the addition of any instrumentation equipment and can be easily implemented when configured in the control system. It can not only protect production equipment and personal safety to the maximum extent, but also avoid the occurrence of erroneous motor temperature protection actions to the maximum extent, and reduce erroneous parking under abnormal conditions as much as possible.

[0006] The technical solution of the present invention is a logic design method for motor temperature protection in a control system, characterized in that: by adding a rate calculation module to judge the change rate of the "output value" signal in the input module, a rate exceeding limit signal is issued when the change rate exceeds the set value, and the logic calculation module performs logical operations on the "bad value", "too high protection value" and "rate exceeding limit" signals to achieve protection output and alarm output.

[0007] In the aforementioned logic design method of a motor temperature protection in a control system, the input module processes the signal sent by the temperature measuring element, and outputs "bad value", "too high protection value" and "output value" signals. The "output value" signal is judged by the rate calculation module for its change rate. When the change rate exceeds the set value, a "rate limit exceeding" signal is issued. The logic calculation module performs logical operations on the "bad value", "too high protection value" and "rate limit exceeding" signals, and outputs "protection output" and "alarm output" signals. The alarm module generates an alarm after receiving the "alarm output" signal, and the output module executes a protection action after receiving the "protection output" signal.

[0008] In the aforementioned logic design method of a motor temperature protection in a control system, in the logic calculation module, the "bad value" and the "rate exceeding limit" are ORed together, and then latched by the Rs trigger, and after being negated, they are ANDed together with the "over-high protection value" to output a "protection output" signal.

[0009] Beneficial effects of the present invention: Compared with the prior art, the present invention does not need to add any instrument equipment after adopting the above motor temperature protection logic method, and can be easily implemented when configured in the control system. Practice has proved that the method is simple and applicable, and can not only protect the production equipment and personal safety to the maximum extent, but also avoid the occurrence of false motor temperature protection action to the maximum extent, and reduce false parking under abnormal conditions as much as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a logic diagram of temperature protection inside the existing control system; Figure 2 It is a schematic diagram of the internal temperature protection logic of the control system of the present invention; Figure 3 It is a logic diagram of the logic calculation module in the control system of the present invention. DETAILED DESCRIPTION

[0011] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the present invention.

[0012] An embodiment of the present invention is a logic design method for motor temperature protection in a control system to overcome the disadvantage of possible erroneous protection action in the prior art.

[0013] As we all know, the principle of temperature measurement by thermal resistors is based on the property that the resistance of metal conductors increases with the increase of temperature. The thermal resistor wire is very thin, which can easily cause the wire to break. At this time, the resistance of the thermal resistor will increase. In addition, when our wiring terminals are in poor contact, the resistance of the thermal resistor will also increase. For the control system, the temperature value of its "input module" will suddenly increase. Generally speaking, the "bad value" of the "input module" will be true at this time. Figure 1 The temperature protection logic operation will result in no protection action output, but in actual production operation, protection action occasionally occurs.

[0014] After multiple online tracking, we found that since the thermal resistor does not necessarily break immediately when it is disconnected, there may be a certain delay, and this delay time is often short or different, and sometimes there is basically no delay, which causes the temperature value of the "input module" in the control system to suddenly increase, and at this time the "bad value" of the "input module" may be false, and it will become true after a delay. This causes the occurrence of false protection action, and this delay is irregular and feasible, and the "delay module" cannot solve the problem of false protection action, but the temperature changes very quickly at this time, so we can solve the delay problem by calculating the rate of change of temperature, and add the "bad value" to design a temperature protection logic with a relatively satisfactory control effect.

[0015] The temperature protection logic designed by the present invention is as follows: Figure 2 As shown, in addition to introducing the judgment of "bad values", the key lies in introducing the judgment of the rate of change of temperature values.

[0016] By adding a rate calculation module, the rate of change of the temperature value (i.e., the "output value") can be judged. When the rate of change exceeds the set value, a "rate limit exceeding" signal is output. The logic calculation module performs logical operations on the "bad value", "too high protection value", and "rate limit exceeding" signals to achieve protection output and abnormal alarm output.

[0017] Specifically: the input module processes the signal sent by the temperature measuring element, and outputs "bad value", "too high protection value" and "output value" signals. The rate calculation module judges the change rate of the "output value" signal. When the change rate exceeds the set value, a "rate limit exceeding" signal is issued. The logic calculation module performs logical operations on the "bad value", "too high protection value" and "rate limit exceeding" signals, and outputs "protection output" and "alarm output" signals. The alarm module generates an alarm after receiving the "alarm output" signal, and the output module executes the protection action after receiving the "protection output" signal.

[0018] At this time, the logic of the logic calculation module is as follows Figure 3As shown, the abnormality judgment of the temperature measuring element is made by the "bad value" and "rate exceeding limit" signals, which are then latched by the Rs trigger, negated and ANDed with the "over-high protection value" signal to output the "protection output" signal.

[0019] This temperature protection logic design introduces the judgment of "bad value", eliminating the occurrence of false protection actions caused by input module device status errors and channel failures. At the same time, it introduces the judgment of "rate limit exceeding", which can eliminate the occurrence of false protection actions caused by delays when the temperature measuring element is disconnected and large fluctuations in the temperature value caused by poor terminal contact. While reducing the occurrence of false protection actions, it does not affect the occurrence of safety protection actions in emergency situations, so as to achieve the best control effect.

Claims

1. A logic design method for motor temperature protection in a control system, characterized in that: By adding a rate calculation module to judge the change rate of the "output value" signal in the input module, a rate-exceeding signal is issued when the change rate exceeds the set value. The logic calculation module performs logical operations on the "bad value", "too high protection value" and "rate-exceeding" signals to achieve protection output and alarm output.

2. The logic design method of a motor temperature protection in a control system according to claim 1 is characterized in that: The input module processes the signal sent by the temperature measuring element, and outputs "bad value", "too high protection value" and "output value" signals. The rate calculation module determines the change rate of the "output value" signal, and sends out a "rate exceeding limit" signal when the change rate exceeds the set value. The logic calculation module performs logical operations on the "bad value", "too high protection value" and "rate exceeding limit" signals, and outputs "protection output" and "alarm output" signals. The alarm module implements an alarm after receiving the "alarm output" signal, and the output module executes a protection action after receiving the "protection output" signal.

3. The logic design method of a motor temperature protection in a control system according to claim 2 is characterized in that: In the logic calculation module, "bad value" and "rate exceeding limit" are ORed and then latched by the Rs trigger, which is negated and ANDed with the "over-high protection value" to output a "protection output" signal.

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