On July 1, 2014, the railway system carried out the largest adjustment since 2007, and the “green leather car†of some road bureaus has since become history. The highest temperature record in the "green leather car" in summer is 59 ° C, the conductor's blue uniform has been basically soaked, the passengers are not fans. In order to improve the comfort of the interior environment of the cabin, the air conditioning system becomes an indispensable part of the locomotive.
The air conditioning automatic control system measures temperature changes based on a temperature sensor. The ambient temperature is regulated and controlled by the main control part of the system. The regulated components include the condenser motor, the evaporator motor, etc. Once the components fail, the system transmits the temperature information to the display screen, and promptly informs the relevant staff to perform maintenance. .
The air conditioning automatic control system is mainly divided into three parts: the main control module, the communication module and the signal processing module.
As the brain of the whole system, the main control module sends various commands to the sub-module to adjust the temperature; the communication module mainly transmits the temperature information to the display device, and accepts the setting content of the main control unit for the temperature information; the signal processing module is responsible for monitoring The physical quantity (temperature, humidity, etc.) of the overall system environment is converted to digital signals for the main control system.
The application block diagram of the air conditioning automatic control system is as follows:
Air conditioning automatic control system for power module selection requirements:
For different power supply conditions, the power module selection requirements are as follows:
1. The main power supply system supplies 110VDC for rail transit, and the module needs to meet the railway wide voltage (66-135VDC) input. At the same time, in order to improve system reliability, it is necessary to ensure that the output is isolated from the power supply. In addition, the module needs to work in vibration for a long time, so its anti-vibration and impact resistance requirements are relatively high;
2. In terms of signal acquisition, positive and negative op amps are generally used for processing, and a wide range of information is obtained and returned to the MCU for processing to obtain physical quantity information such as temperature and humidity. Its power supply can be powered by the main power supply, so its input voltage can be input with a constant voltage. In addition to the power conversion function, in order to prevent signal processing circuits and digital circuit crosstalk, the power supply must be isolated. At the same time, in order to improve the stability of the system, the smaller the ripple noise of the module, the better;
3. Adopt CAN bus communication method in communication. In order to improve communication reliability, communication needs to be isolated to prevent mutual interference of communication devices. Communication equipment needs to support multi-node communication, so the same node of the communication module is required to support multiple nodes.
Recommended Products
For the output voltage of the above power supply and the power corresponding to the chip, the recommended power supply is as follows:
In terms of circuit design, because the railway power supply has high reliability and EMC requirements, and our power supply itself has no EMC protection, it is necessary to design EMC protection circuit at the front end of the module. It is recommended to use FC-CX1D module to achieve higher EMC rating:
Parameter recommendation:
FUSE (Fuel): According to the customer's actual input current selection;
C0: 100uF/200V electrolytic capacitor is recommended; it is used to suppress voltage sag, and applications without this requirement may not be designed;
CY1, CY2: 1nF/2KV capacitor.
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