Introduction

IRST series variable inductance resonant test systems are designed to compensate capacitance in testing circuit precisely by adjusting inductance of HV reactors, when test system gets in resonance, it outputs continuous AC voltage of power frequency (mainly 50 or 60Hz, matches feed-in mains).

IRST series HV reactors, main part of the system, work on fixed frequency and variable inductance, are of oil insulation and epoxy glass-fiber insulating shell, module type and stackable, voltage up to 2000kV.

These systems offer significant advantages to standard AC test systems where the load is largely capacitive.

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.