Open-loop Hall-effect transducers measure to 250A

May 21, 2014 // By Graham Prophet
LEM has extended the measurement range of its HO series current transducers up to 250A; a the same time it has further improved the specifications which continue to edge close to what is achievable with the – more complex and costly – closed-loop techniques.

These moulded components are configured either with primary conductors installed, for PCB mounting; or with apertures that accept a primary conductor (cable). Using LEM's in-house-designed ASIC, they measure up to 250A DC, AC or pulsed, with over-current detection and fault reporting, over an operating temperature range from -40 to +105ºC,

By orienting a single snap-on moulding in different positions, the same unit can be panel-mounted in different orientations or can be locked to a busbar that is the primary conductor. HO series current transducers measure DC, AC, and pulsed signals using the latest generation of LEM’s Open-loop Hall-effect Application Specific Integrated Circuit (ASIC) which was introduced with the launch of the HO 8, 15, 25-NP and -NSM series and the HO 6, 10 and 25-P models.

The new series offer offset and gain drifts which are up to twice as accurate across the temperature range as the previous generation and have a faster response time of 2.5 to 3.5 µsec. Operating from a single supply voltage of 3.3V or 5V, the HO series can measure up to x 2.5 the primary nominal current and integrate an additional pin which provides over-current detection set at x 2.93 the nominal current I PN (peak value). This threshold detection is completely independent of the main measuring circuit, which maintains full resolution. They also provide fault reporting in the event of memory corruption.

High clearance and creepage distances of more than 8mm and a Comparative Tracking Index (CTI) of 600 mean that, despite small packages of 22.95 cm3 to 33.15 cm3, there is no compromise on the insulation level provided between the primary and measurement circuits.