LEM Current Transducers

Open-loop Hall sensors measure magnetic field directly using a Hall element, offering simple structure, lower cost, and smaller size. They typically provide 1-2% accuracy with 10-50kHz bandwidth, suitable for general industrial applications. Closed-loop Hall sensors use a compensation coil and feedback mechanism to null the magnetic field, achieving 0.1-0.5% accuracy with 100-200kHz bandwidth. Closed-loop sensors have better linearity, lower temperature drift, and faster response but are larger, more expensive, and consume more power. Choose open-loop for cost-sensitive applications and closed-loop when high precision is required.

Choose open-loop sensors (HLSR series) for cost-sensitive applications like HVAC, lighting control, and general motor monitoring. Choose closed-loop sensors (CAS, HAIS series) for precision applications like servo drives, power analyzers, and medical equipment where accuracy is critical.

When selecting current range, consider: 1) Normal operating current - typically 50-80% of rated current for optimal accuracy

2) Peak current - ensure the sensor can handle transient overcurrents (most LEM sensors handle 2-3x rated current)

3) Safety margin - select rated current 20-30% above maximum expected current

4) Measurement resolution - smaller range provides better resolution but less headroom

5) Future expansion - consider potential system upgrades. For example, if your motor drive has 50A nominal current with 100A peak, a 100A rated sensor would be appropriate, providing good resolution while handling peak currents safely.

For best accuracy, operate the sensor at 50-80% of rated current. Choose a sensor with rated current 1.3-1.5x your maximum continuous current. For applications with high inrush currents (motor starting, transformer energization), verify the sensor can handle the peak without saturation.

LEM current transducers provide galvanic isolation between primary (measured) and secondary (output) circuits. Standard industrial models typically offer 2.5kV to 6kV isolation voltage (RMS), tested according to IEC 61010-1 standards. High-voltage models can provide up to 12kV isolation for specialized applications. The isolation ensures safety by preventing high voltages from reaching low-voltage control circuits and eliminates ground loop issues. All LEM sensors undergo 100% production testing for dielectric withstand voltage. For specific isolation requirements in your application, consult the datasheet or contact our FAE team for guidance.

For standard industrial applications (up to 600V systems), 2.5kV isolation is sufficient. For high-voltage EV battery systems (400V-800V), select sensors with 3kV or higher isolation. For grid-tied applications, consider sensors with 5kV or higher isolation ratings.

Yes, LEM Hall effect current transducers can measure both DC and AC currents. The Hall effect principle responds to the magnetic field generated by current flow, regardless of whether it's DC or AC. For DC measurement, the sensor provides a stable output proportional to the DC current. For AC measurement, the sensor accurately tracks sinusoidal and non-sinusoidal waveforms. The bandwidth specification indicates the maximum AC frequency the sensor can accurately measure - typically 10-50kHz for open-loop and 100-200kHz for closed-loop sensors. Some LEM models can also measure complex waveforms including PWM signals common in motor drives and inverters.

All LEM current transducers measure both DC and AC. For pure DC applications like battery monitoring, any LEM sensor will work. For AC applications, consider the bandwidth requirement - standard 50/60Hz power monitoring works with any sensor, while high-frequency PWM applications need higher bandwidth closed-loop sensors.

LEM current transducers are used in diverse applications: 1) Industrial drives - Motor current monitoring, overcurrent protection, vector control

2) Power supplies - Input/output current monitoring, PFC circuits, DC-DC converters

3) Renewable energy - PV inverter DC/AC current measurement, wind turbine power monitoring

4) Electric vehicles - Battery management current sensing, motor controller feedback, charging station monitoring

5) UPS systems - Battery charge/discharge monitoring, inverter current feedback

6) Welding equipment - Primary and secondary current control

7) Medical equipment - Isolated patient safety monitoring

8) Test equipment - Precision current measurement and analysis.

For motor drives and industrial automation, HLSR or CAS series are commonly used. For EV battery management and automotive, HO or HMSR series with AEC-Q100 qualification are required. For high-precision test equipment, CAS or HAIS series provide the best accuracy.

LEM current transducers support multiple mounting options: 1) Panel mount - Secure with screws through mounting holes, pass conductor through aperture

2) PCB mount - Solder pins directly to circuit board, conductor routed through sensor

3) Busbar mount - Attach to busbar system for high-current applications. Wiring considerations: Connect supply voltage (+Vs, -Vs or GND) as specified

output connects to measurement circuit (voltage or current output)

ensure proper polarity for DC measurements. For best performance: Keep primary conductor centered in aperture

avoid external magnetic fields

use twisted pair for output cables in noisy environments

maintain specified operating temperature range. Always refer to the specific product datasheet for detailed installation instructions.

For new PCB designs, PCB-mount sensors like HLSR or HMSR offer the most compact solution. For retrofit applications or high currents, panel-mount sensors like CAS or HTFS are easier to install. For busbar applications, HAIS series provides robust mounting options.