© by SEMIKRON
/ 2017-09-07 /
Technical Explanation
/ SKiiP
®
4
Page 41/73
The value f0
Iana
given in the Table 5—8 is marked in Figure 5.29. At this frequency the amplitude is still not
significantly damped.
Figure 5.29: Bode diagram of the AC-current measurement at the
SKiiP
4 interface
Current sensor working principle
The current transformers operate using the compensation principle. The magnetic field generated by the
load current is detected by a magnetic field sensor. This is a small coil with a high permeable core. Due to
the properties of this sensing element there is low gain and linearity failure. An electronic circuit evaluates
the value of the field sensor and feeds a current into the compensation coil to keep the effective magnetic
field at zero. The demanded compensation current measured by a burden resistor. A measurement circuit
generates a voltage that is proportional to the load current. The SKiiP
®
4 current sensor uses a switch mode
controller for the compensation current. Figure 5.30 illustrates the compensation principle with the current
sensor employed in the SKiiP
®
4.
Figure 5.30: Compensation principle of SKiiP
®
4 current sensor