Mine frequency converter is a power control device that uses frequency conversion technology and microelectronic technology to control the AC motor by changing the frequency of the working power supply of the motor. The frequency converter is mainly composed of rectification, filtering, inverter, braking unit, drive unit, detection unit and micro-processing unit. By changing the frequency of the power supply to achieve the purpose of changing the power supply voltage, according to the actual needs of the motor to provide the required power supply voltage, and then achieve the purpose of energy saving and speed regulation.
China is rich in mineral resources, especially iron ore, coal, phosphate, rare earth and other minerals. With the improvement of mining mechanization, safe operation is a top priority. Mine frequency converters are an important equipment for mining electrical systems. , The role is also crucial. The energy saving of mine inverter is mainly reflected in the application of fans, transmission, mine vehicles, hoists, mining and other equipment. In order to ensure the reliability of production, all kinds of production machinery have a certain surplus when they are designed with power drives. When the motor cannot run under full load, in addition to meeting the power drive requirements, the excess torque increases the consumption of active power, resulting in a waste of electrical energy.
2. The principle of Hall current sensor
The Hall current sensor is based on the magnetic balance Hall principle, that is, the closed loop principle. When the magnetic flux generated by the primary current IP is concentrated in the magnetic circuit through the high-quality magnetic core, the Hall element is fixed in the air gap to detect the magnetic flux. The multi-turn coil on the magnetic core outputs a reverse compensation current, which is used to cancel the magnetic flux generated by the primary IP, so that the magnetic flux in the magnetic circuit is always kept at zero. After processing by a special circuit, the output of the sensor can output a current change that accurately reflects the primary current.
3. Basic requirements of Hall current sensor
There are many domestic manufacturers of Hall current sensors, and there is no difference in principle, but there are differences in the selection of components, production technology, and process control of product production. We use the current commonly used in the mine inverter industry. The sensor JCE508-TS6 product is taken as an example. It has been tested by the China Aerospace 513 Research Institute and passed the certification of the Aerospace Institute. The basic technical parameters are as follows:
Model: JCE508-TS6
Rated measuring current IPN: 500A
Measuring range IP: 0 ~ ± 800 A
Rated measurement output IM: 100mA
Power supply voltage (± 5%): ± 15V ~ ± 18V
Conversion ratio KN: 1: 5000
Current consumption IC: ≤20 (@ ± 15V) + IS mA (output measurement current)
Accuracy X: —Accuracy XG (@VPN, TA = + 25 ℃): ± 0.6%
—Non-linearity εL (@VPN, TA = + 25 ℃): "0.1%
—Zero offset current IO: ≤ ± 0.15mA (@ + 25 ℃)
—Zero temperature offset IOT: ≤ ± 0.49mA (@ -10 ℃ ~ + 70 ℃)
—Response time tr (@ 90% of VP max): ≤1us
—Working frequency f: DC-100KHz
Withstand voltage Vd: withstand voltage between primary side circuit and secondary side circuit: 6kV / 50 / 60Hz / 1min
Working temperature TA: -25? C ~ + 80? C
Secondary side internal resistance RS: 60Ω (TA = 70 ℃)
After testing its response time and output signal, the relevant curve is obtained as follows:
4. Issues to be noted when choosing a current sensor
1) When selecting the sensor, pay attention to the ambient temperature of the product. The industrial grade cannot meet the basic requirements, and must be -40 ° C-85 ° C;
2). The altitude requirement is above 3500 meters;
3) When selecting the sensor, the range can be appropriately larger, leaving room for product overload. Note that the closed-loop current sensor cannot be overloaded for a long time;
4) For the selection of terminals, railway-specific anti-vibration terminals should be used as much as possible to avoid falling off due to strong earthquakes during transportation or operation of the inverter;
5) Do not allow the sensor to be used under wet conditions to avoid the product from working normally due to condensation and humidity;
6) Since the casing of the mine inverter belongs to the explosion-proof level, the current sensor is required to be shock-proof, and the explosion-proof is not required too much.
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