Innovative Current Sensor without Toroidal Magnetic Core Offers New Design Advantages

The conventional approach for AC/DC current sensors or current converters is to place a soft toroidal magnetic core with an air gap around the live conductor. If a magnetic field sensor is then introduced into this air gap, its output signal is proportional to the flowing current (see Figure 1). It should be noted that alternating current (AC) can be measured with current converters based on converter technology, whereas this is not possible with DC currents.Get more news about Current sensor core,you can vist our website!

This measuring principle works well with currents of up to approximately 1,000 A. Over 1,000 A, the required sensor becomes quite voluminous and expensive: the stronger the current, the larger the cross-section of the core must be in order to avoid saturation. However, the magnetic core performs various functions:

The magnetic flux is focused on the magnetic field sensor.
The sensor is less sensitive to magnetic stray fields.
The magnetic flux can easily be amplified by additional primary windings.
However, as the current increases, the core becomes less useful and more of a disadvantage.

Modern magnetic field sensors do not require a strong magnetic flux to achieve high precision. Instead, saturation effects in the core affect accuracy. If, however, the toroidal core is omitted completely, you will face the well-known problem of signal distortion due to stray magnetic fields, which usually originate from other nearby conductors, and the influence of the terrestrial magnetic field. But there is an interesting solution to these problems based on differential measurement of the magnetic field.
Differential Current Measurement
This technique eliminates the effects of uniform magnetic stray fields in a very simple but effective way (see Figure 2). In cases where the stray fields are not uniform, the two sensors are placed as close as possible to each other. In order to increase the magnetic field strength, the bus bar can be tapered locally. This local constriction increases the resistance only slightly.
The conventional approach to differential current measurement involves installing a sensor on each side of the conductor. Raztec recognized that it would be advantageous to measure the current inside the bus bar by drilling into it or – to put it another way – sounding it out. This is where the name Current Probe for this innovative sensor comes from, shown in Figure 3 here.

Probe instead of Converter
The format of the probe allows a considerable reduction in the size and weight of the sensor. In fact, the smaller the sensor, even the better. Figure 5 clearly illustrates the considerable difference in size compared to a classic push-through sensor. The one-sided mounting of the probe considerably simplifies tapping of the current.

In principle, the sensor can even be retrofitted without dismantling the bus bar. As the current increases, the cross-section of the bus bar increases, too, which means that the magnetic flux changes only slightly. Therefore, the current probe can remain unchanged even at higher currents: It can measure 1,000 A as well as 25,000 A.