LEM FRS, FL - OPEN LOOP CORELESS INTEGRAL SENSORS

LEM's new FRS and FL product families are designed for electronic measurement of DC, AC, and pulsed current with galvanic separation between primary and secondary circuits.

The two new coreless high current sensors accurately measure high DC currents from 2kA to 42kA, unaffected by surge currents. The Open Loop Coreless Integral (OLCI) sensors have wide openings for precise measurement of high currents on large busbars, and they can handle high-frequency applications with a bandwidth of up to 1MHz. These sensors are also considerably lighter, weighing just 80% of what comparable open loop or closed loop current transducers weigh, and they are more cost-effective.

LEM offers two variations of the new OLCI high current sensors: the FRS model, which can accommodate primary busbar openings of 104mm x 22mm, and the FL variant, which can handle openings up to 300mm x 100mm. The FL sensor features a split transducer design, allowing for convenient installation and connection to the busbar without the need to open the busbar, simplifying the installation and maintenance process.

FRS current sensors measure currents up to 9000A, while FL sensors can measure up to 42kA. Both product families are available with either a current output (4-20 mA) or an instantaneous voltage output (0-5 V).

The main difference between the two product families lies in the size of the sensor: FRS sensors have a 104mm aperture, whereas FL sensors are available with either a 200mm or a 300mm aperture width.

Utilizing OLCI (Open Loop Coreless Integral) technology, FRS and FL coreless transducers ensure reliable and accurate current measurements in industrial, traction, and trackside applications. The sensors feature a large aperture for accurate measurement of high currents on large busbars, with up to 1MHz bandwidth for high-frequency applications. They are also significantly lighter (80%) and more cost-effective than open loop or closed loop current transducers operating within the same current measuring range.

Current measurement is evolving with clear trends towards smaller physical sizes, higher current ranges, cost savings, and quicker response times for faster switching frequencies, particularly in UPS systems and renewable power generation. Open-loop sensors are increasingly favored for achieving these objectives due to their simplicity.

Traditionally, closed-loop sensors have been used to meet the accuracy and speed requirements of high-current measurements. However, the inclusion of a secondary coil to cancel the magnetic field from the measured current increases the device's size, current consumption, complexity, and cost. In high-current applications, the secondary coil requires a high-supply voltage or complex electronics.

A more efficient approach utilizes an open-loop architecture, where a complex ASIC serves as the magnetically sensitive element to address the imperfections inherent in open-loop systems. This technique, previously used in low-current sensors, involves measuring any sensitivity or offset errors, including temperature drift, during ASIC production testing. These corrections are then continuously applied during use, allowing most electrical parameters to match the performance levels of the previous generation of closed-loop sensors.

FRS and FL: Eco-Friendly Current Sensors for the Renewable Energy Industry

• Based on Open Loop Coreless Integral (OLCI) technology
• Measure DC currents from 2kA up to 42kA without surge current limitations
• Fast response time, 1MHz bandwidth
• 80% less weight
• 85% less energy consumption
• 100% recyclable/recoverable material at end of life

FRS Model:

• Measures 1,000 to 3,000A
• Supports primary busbar aperture of 104 x 22mm

FL Model:

• Measures 12,000 to 28,000A
• Split sensor for easy and flexible installation up to 300 x 100mm aperture

Features:

• Hall effect Open Loop Coreless Integral current sensor
• Unipolar or Bi-polar measurement of primary current up to 42kA
• Instantaneous 4-20 mA current output or Instantaneous 0-5 V voltage output
• Power supply: +12 or +24 V DC
• Galvanic separation between primary and secondary circuits
• Factory calibrated

FRS sensors, which ensure unipolar or bi-polar measurement of primary current up to 9000A, also feature high bandwidth (> 1MHz) and very low delay time (< 400 ns).

Main Characteristics:

• Wide measurement range
• No magnetic offset
• Low consumption and low losses
• Wide range of rectangular busbar dimensions
• Lightweight design
• M12 field connector

Typical Applications: Both FRS and FL coreless high current sensors, known for their ability to measure DC, AC, and pulse currents, are widely used in various industrial areas, as well as in traction and trackside applications. Examples include:

• Wind turbine power converters
• Electrolysers
• High power drives