Isolated current sensors are fast for motor control

Called RAZC, there are multiple devices, sensing between 40Amax and 250Amax, all with a 10mm outside diameter, and the manufacturer offers custom versions as well.

Bandwdth is generally in hundreds of kHz (see table below) and the standard rise time is 5µs for a 0-20A step.

Typically non-linearity, hysteresis and temp co/°C are all a small fraction of 1% – check the data sheets for detail (accessible from this page).

Over-current handling is limited by the conductor rather than the sensor.

Motor winding current sensing is a typical application.

“The toroidal current sensor simply encircles a motor connection. Galvanic isolation completely eliminates common mode effects and true armature current is accurately measured,” according to the firm. “The output of the sensor is near rail to rail so no amplification is required – current signals can be fed directly to an A/D.”

Applications in solar power generation and battery management are also foreseen.

The hole through the sensor is 5.1mm in diamater, although a protrusion reduces the maximum allowable round cable size 4.5mm.

There are three connections, Vcc, ground and output, where the output is biased close to Vcc/2 for 0A.

Table created from Raztec data sheets – errors may have occurred during transcription.

* to customer spec