Tettex MIDAS 2881, Operating Instructions Manual

Page: 101 / 164

Accessories and Options 91
8.4 Resonating Inductor
General
The capacitive load range covered by the MIDAS system can be increased using a Compensating
Reactor (resonating inductor).
C
X
Capacitance (DUT) to be
measured
C
N int.
Standard capacitor
U
Test
Test voltage, applied to the test
object
L
k
Compensating reactor for test
current extension
R
X
Measuring shunt on the DUT
side
R
N
Measuring shunt on the
Reference (Cn) side
Schematics of test current extension with resonating inductor Lk
A variable reactor coil is connected in parallel with the capacitive test object C
X
. This configuration
constitutes a parallel resonating circuit.
By adjusting L
K
the resonant point can be found and then the resonant circuit draws only a (small)
amount of real power from the mains (through the resistive part of Cx and Lk).
This arrangement allows measurements of capacitances up to:
5288A max. 10 kV max. 45kVA
max. 1

F
5289 max. 15 kV max. 100 kVA
max. 1.56

F
See chapter “Application Guide : Measuring high cap values using the Resonating Inductor” for a
connection example.