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 increase 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.
Mohaupt VFRTS are turn-key solutions designed upon your request.
Max. Voltage (kV)
Max. Current (A)
Min. Frequency (Hz)
No. of reactors
Load Capacity (nF)
(l x w x h)
6,1 x 2,4 x 2,6
6,3 x 4 x 12
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” windings (even though oil insulated). 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 260A per reactor without any thermal restriction and subsequent accelerated aging, due to thermal heating of the insulation.