More and more new technologies have been integrated into small power supply devices. For example, switch power supplies, hard switches, soft switches, parameter adjusters, linear feedback adjusters, magnetic amplifier technology, digital control voltage regulation, PWM, SPWM, electromagnetic compatibility, etc.

The actual demand directly promotes the continuous development and progress of power supply technology.

In order to automatically detect and display current, and have automatic protection and higher intelligent control capabilities in dangerous situations such as overcurrent and overvoltage, power technology with sensor detection, sensor sampling, and sensor protection functions is becoming a trend. Current or voltage detection sensors have emerged and are widely used in China.

It is favored by large power supply designers.

As a key component in frequency converter control, current sensors play an important role in ensuring the performance of the frequency converter.

Currently, many malfunctions of certain frequency converters in the market are caused by damaged current sensors or improper use.

The following introduces the application of current sensors in frequency converters. Usually, matching current sensors have corresponding power supplies of ± 12V and ± 15V; The regulating circuit constitutes a current sampling module, which converts the three-phase stator current into basic binary code, provides timely current information, and completes the regulation of the current loop. The system uses three JCE modules (some frequency converter manufacturers also use two, with the third one completed by an algorithm) to detect phase A, B, and C currents respectively.

The current information is converted into voltage information through sampling resistors, and then converted into digital signals through the AD conversion module in the main control chip of the frequency converter. After digital filtering and calibration, current feedback information will be provided for current loop regulation. The hardware schematic diagram of the detection circuit is as follows:

JCE current sensors convert current information into voltage information. In addition, it also converts the signals detected by LEM into a voltage range suitable for controlling the chip. Firstly, the voltage signal is converted into symmetrical positive and negative voltages, and then the corresponding offset is provided to convert it into a voltage range suitable for the control chip.

JCE samples the three-phase currents of A, B, and C and stores them in the corresponding registers for use by the main control system after the detection module.

Usually, a three wire system is used. The sum of the three-phase currents of the motor stator is equal to zero. The LEM component samples the three-phase currents of A, B, and C. The conversion result after the detection module is used as the basis for detecting the three-phase current imbalance rate; In addition, after the inverter cuts off the output, LEM components can be used to detect the three-phase currents of A, B, and C to determine whether the power module is reliably shut down and eliminate potential safety hazards.

In applications, JCE sensors have many characteristics

Powerful overload capability: When a current overload occurs, it can automatically protect the sensor, even if the overload current is 20 times the rated value, the sensor will not be damaged;

The capacitance between the primary and secondary sides is very weak. In many applications, the influence of * mode voltage can be ignored;

High sensitivity: It can distinguish between high component weak signals and small signals, such as several Ma AC components of several hundred amperes of DC current;

High reliability: Failure rate: λ=0.43 × 10-6/h; Strong resistance to external magnetic fields: At a distance of 5-250px from the sensor, the error caused by magnetic field interference caused by double operating current is less than or equal to 0.5%.

It can measure the current of any waveform, such as DC, AC, pulse waveform, and even transient peak values;

The primary and secondary circuits are completely insulated. The insulation withstand voltage is generally 3-6kV, and special requirements can reach 6-50kV;

High measurement accuracy: within the working temperature range, the accuracy is better than 1%, suitable for any waveform measurement;

Good linear performance: better than 0.5%;

Response time less than 1 μ s, tracking speed di/DT greater than 50A/μ s;

Working bandwidth: The accuracy within the range of 0 (DC) to 100kHz can reach 1%, and the accuracy within the range of 0-5kHz can be improved to 0.5%;

Practice has proven that the current detection loop composed of JCE current sensors and regulating circuits can fully meet the current detection requirements of closed-loop control of frequency converters.

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