Introduction:

FRST series variable frequency resonant test systems vary the output frequency to tune the system to create resonant circuit with load capacitance, then output pure sine wave AC voltage for testing, typical frequency range is 20~300Hz.

FRST series HV reactors, main part of the system, are of oil insulation and epoxy glass-fiber insulating shell, module type and stackable, serial connect for higher voltage, parallel connect for larger current, voltage up to 2400kV.

These systems are ideal for field commissioning test of power cables and GIS/GIL.

Application:

AC resonant test systems are mainly used to output AC voltage for high voltage routine, type and development testing of capacitive test objects. These systems exert the principle of series resonance, as per f=1/2π√LC, the connection of HV reactors (inductance L) to a capacitive loads (capacitance C) form an oscillating circuit with the frequency (f) of power supply.

Compared to conventional AC test transformers, the relatively lower power required (1/Q), smaller dimension and lighter weight favor these systems as the most practical for field testing, and large capacitance loads.

Configuration

Principle:

Series resonant circuit consists essentially of an inductor in series with a capacitive test object or load connected to a medium-voltage power source. Alternatively it may consist of a capacitor in series with an inductive test object. By varying the circuit parameters or the supply frequency, the circuit can be tuned to resonance, when a voltage considerably greater than that of the source and of substantially sinusoidal shape is applied to test object.

The stability of the resonance conditions and of the test voltage depends on the stability of the supply frequency and of the test system characteristic, described by the quality factor, which is the ratio between test reactive power and power loss.

When a discharge occurs, the circuit capacitance discharges instantaneously and then follow-through current from the source is relatively low. The limit follow-through current generally results in less damage to the test object.