Tuesday, October 09, 2012

LEM uses Fluxgate technology to reduce current transducer size by 30 percent

LEM has introduced several ranges of PCB-mounted current transducers housed in a package 30 percent smaller than the company’s LTS devices. The CAS, CASR and CKSR family of transducers are intended for AC and DC isolated current measurement from 6 to 50ARMS nominal, up to 3 times the nominal values for the peak measurement and up to 300kHz (+/-3dB). All the models (6 ARMS, 15 ARMS, 25 ARMS and 50 ARMS) are housed in the same compact package and can be set up on PCB according to the needs for different ranges from 1.5 ARMS to 50 ARMS (according to the models).

The new transducers have been specially designed to respond to the technology advances in drives and inverters, which require better performance in areas such as common-mode influence, thermal drifts (offset and gain; Max thermal offset drift for the models with reference access: 7 to 30 ppm/K according to the models), response time (less than 0.3 microseconds), levels of insulation
and size.

To obtain this performance the Closed Loop Fluxgate technology has been used. This enables LEM to combine high accuracy and attractive price without compromising any of the advantages of the LTS family, such as size, dynamic performance and wide measuring range.

Although the new transducers are 30 percent smaller than the existing LTS family, their insulation performance allows use in industrial applications without a special layout of the PCB. The CTI (Comparative Tracking Index) of the plastic case is 600. The CKSR model has one more primary pin than the three pins of the CAS and CASR models and a different primary footprint enabling higher creepage and clearance distances of 8.2mm to be achieved. This is particularly useful when
higher insulation is required in applications with high working voltages such as 600 VRMS according to the EN 50178 standard. Moreover, this additional primary pin allows a configuration of the CKSR 6-NP model for a nominal current range of 1.5 ARMS.

All transducer models have been designed for direct mounting onto a printed circuit board for primary and secondary connections. They all operate from a single 5 V supply. The CASR and CKSR models provide their internal reference voltage to a VREF pin. An external voltage reference between 0 and 4V can also be applied to this pin.

The CAS, CASR and CKSR family of transducers are suitable for industrial applications such as variable speed drives, UPS, SMPS, air conditioning, home appliances, solar inverters and also precision systems such as servo drives for wafer production and high-accuracy robots.

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