Frequency Tuned Resonant Test SystemAir Insulated



Variable frequency test set (VFRTS) are suitable for long-term, factory and on-site testing of high capacitive test objects as e.g. power cables, capacitors or others. VFRTS are of modular design for series or parallel connection of more units to in-crease the test current or the test voltage.

The maximum testing capacity depends on the minimum frequency on which the system is designed for. With decreasing frequency, the maximum load increases. MHV VFRTS provide a minimum frequency of 10Hz, due to the ironless reactor design. Compared to 20Hz this provides a 4-time higher load.

Using more reactors increases the flexibility of the system. With stacking reactors, higher output voltages are achieved at the nominal current. Parallel connection increases the current.
Especially for on-site testing application an air-insulated and air-cooled design is of advantage. Not only environmental consideration, but also transportation weight and robustness towards weather and transportation might be of big importance to choose this type of system.

Mohaupt VFRTS are turn-key solutions designed on request.


  • Due to the low-loss design and high Q-values of the reactors (well above 100 for power frequencies, above 60 at 10Hz), the losses and required feeder power is at a minimum
  • Modularity allows an flexible adaption of the test setup to the requirements of the test object
  • Suitable for laboratory and on-site application application
  • Reliable operation in industrial environment
  • High Q-factors means low power consumptions and low weight
  • Robust design electrically, thermally and mechanically
  • Due to modularity very flexible adaption to the specific testing situation
  • Available as cylinder solution in different setups

Technical Data

TypeMax. Voltage (kV)Max. Current (A)Minimum Frequency (Hz)No. of reactorsLoad Capacitance (nF)Weight (t)Dimension (l x w x h) m
PCR175-5-10Cylinder3502010420001913 x 2,4 x 2,6


The key to expand the load range down to a minimum frequency of 10Hz and keep a high quality factor is, to use reactors of ironless design. Conventional reactors do have an iron core. The iron core generates additional losses in addition to the copper losses of the wire. At low frequencies the induction of the iron core increases. In order to maintain the required design limits, an increase of the iron cross section is required, increasing losses and weight. This drawback is overcome by MHVs ironless design. The reactors consist of air-insulated and air cooled windings. These windings provide excellent electrical performance in steady state operation, as well as in transient conditions (flash over or breakdown of test objects). Furthermore, they have substantial better cooling performance compared to conventional reactor windings, enabling currents up to 5A per reactor.

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