A current sensor is a detection device that can sense the information of the current being measured and transform the sensed information into an electrical signal or other required form of information output that meets certain standards, so as to meet the requirements of information transmission, processing, storage, display, recording and control.
Based on different measurement principles, current sensors can be mainly divided into: shunt current transformers, electromagnetic current transformers, and electronic current transformers.
Schematic diagram and appearance of a current sensor
Basic parameters of current sensor
There are many domestic manufacturers of Hall current sensors. The underlying principles are the same; the differences lie in the selection of components, manufacturing processes, and process control during production. Taking the JCE308-TS7 current sensor, commonly used in the charging pile industry, as an example, it has been tested and certified by the China Aerospace 513 Research Institute. Its basic technical parameters are as follows:
Main technical parameters:
Model: JCE308-TS7
Rated measuring current IPN: 300A
Measurement range IP: 0~±500A
Rated measurement output IM: 150mA
Power supply voltage (±5%): ±12V~±15V
Conversion ratio KN: 1 : 2000
Current consumption IC: ≤28 (@±12V) +15mA (output measurement current)
Precision X: — Accuracy XG (@VPN , TA=+25℃): ± 0.6 %
—Nonlinearity εL (@VPN, TA=+25℃): < 0.1 %
—Zero-point offset current IO: ≤ ± 0.15mA (@+25℃)
Zero-point temperature offset (IOT): ≤ ± 0.44mA (@-10℃~+70℃)
—Response time tr(@90%ofVPmax): ≤1us
—Operating frequency f: DC-100KHz
Withstand voltage Vd: Withstand voltage between primary circuit and secondary circuit: 6kV/50Hz/1min
Operating temperature (TA): -40 ° C to +85 ° C
Storage temperature (TS): -40 ° C to +85 ° C
Secondary side internal resistance RS: 21Ω (TA=70℃)
Current sensor electrical parameter curve
Applications of current sensors
There are currently two types of charging stations: AC charging stations and DC charging stations.
The AC charging pile outputs AC200V, which powers the on-board charger of the electric vehicle for charging. The three-phase current at the input terminal is monitored.
A DC charging station consists of a rectifier cabinet and the DC charging pile itself. The DC charging pile typically outputs DC 400V, which can directly charge electric vehicle batteries. Current sensors detect the three-phase current at the charging pile's input terminal (in most cases), and monitoring is also performed at the output terminal of the rectifier cabinet, i.e., the discharge terminal. See the diagram below:
How current sensors can help electric vehicle charging stations
The motor controller, the "central nervous system" of a pure electric vehicle, controls the starting, running, forward and reverse movement, speed, and stopping of the electric vehicle's motor. It is also a core control device for other electronic components. The current sensor within this controller directly affects the vehicle's performance.
As a power measurement element, current sensors play a crucial role in monitoring the charging process and ensuring charging safety. In the process of a charging station converting AC power into standard DC or AC current and delivering it to the vehicle battery, the normal current magnitude at each stage of the conversion system is essential for ensuring a safe and smooth charging process. Current sensors in charging stations can accurately measure the current in critical system components, promptly detecting and reporting internal anomalies such as leakage, thereby preventing safety accidents. Furthermore, another function of current sensors is to accurately measure the amount of electricity charged into the vehicle, displaying this information for user reference and calculating charging fees.
How are current sensors specifically used in new energy vehicle charging stations?
Honeywell CSNK closed-loop current sensor
Honeywell: CSN Series Closed-Loop Current Sensors
The CSN series closed-loop current sensors measure current based on the magnetoresistive or Hall effect, and zero-point balance or zero-flux methods (feedback systems). The magnetic flux in the sensor core is always kept at zero. The current required to balance to zero flux is equal to the primary current flowing through the conductor multiplied by the turns ratio of the primary to secondary coils. Honeywell current sensors feature a through-hole design, isolating the output voltage from the input, and offering advantages such as strong overshoot resistance, fast response, low power consumption, and linear output.
BYD Integrated Current Sensor
BYD: Pioneers Highly Integrated Current Sensor
The BLX9-200I0V1HA current sensor used in BYD's E6 pure electric vehicle and the BSX9-600IOV1HA current sensor used in BYD-Daimler joint venture brand Denza are both based on highly integrated ASIC technology and employ a multi-unit current sensor solution. This solution breaks away from the conventional approach of requiring three sensors, adopting an integrated design that is a first in China.
Compared to conventional solutions, BYD's current sensor solution integrates the Hall effect chip, operational amplifier, filter, and temperature compensation into a single chip, resulting in higher reliability and lower failure rate.
LEM: HABxx-S Series Current Sensor
Previously, the HABxx-S series has been widely used to measure DC, AC, and even pulse currents up to ±250 amps. This sensor incorporates the latest application-specific integrated circuits (ASICs), offering up to 2.5 times higher accuracy and half the offset error compared to previous models, while also significantly reducing the product price.
The new sensor utilizes open-loop Hall effect technology and can detect current simply by being mounted on a conductive cable, effectively simplifying installation and maintenance. The sensor outputs a pulse-width modulation (PWM) signal proportional to the measured source-side current and operates on a single 5-volt power supply. Also currently released is a new type of current sensor with an additional fourth output pin, integrating temperature sensing.
The HAB60-S sensor outputs a standard 125Hz PWM signal with 0.2 % linearity. In the highly turbulent environment inside a vehicle, the PWM signal effectively suppresses output voltage amplitude interference. This is because at a 125Hz carrier frequency, interference only alters the output voltage amplitude, not the pulse duty cycle. The innovative HAB60-S current sensor uses the pulse duty cycle to indicate current magnitude. This series of devices utilizes ultrasonic sealing welding, making them completely waterproof and dustproof, and employs secure connectors to ensure safe use, including in the engine compartment.
The HABxx-S series current sensors have passed all relevant automotive industry certifications and are primarily suitable for current measurement in battery management systems of electric vehicles, hybrid vehicles, and traditional vehicles.
Issues to consider when selecting a current sensor
1) When selecting sensors, pay attention to the ambient temperature of the product's operating environment. Industrial-grade sensors cannot meet the basic requirements; the temperature must be between -40°C and 85°C.
2) The altitude requirement is above 3500 meters;
3) When selecting a sensor, the measurement range can be slightly larger to allow for some overload tolerance. Note that closed-loop current sensors cannot be overloaded for extended periods.
4) When selecting terminals, railway-specific shock-resistant terminals should be used as much as possible to prevent them from falling off during transportation or operation due to strong vibrations.
5) Do not use the sensor in humid conditions to avoid the product malfunctioning due to condensation or moisture.
