Resonance Test Sets for HV testing

[VLFit]

When designing a high power high voltage resonant system for cable or motor and generator testing, or as a general question, when is a separate exciter transformer used in a parallel resonance circuit? They are always used in Series Resonant systems but not in Parallel Resonant systems. When and why the exciter in PR test systems?

 

[HVTS__1]

Power frequency Parallel Resonant Test Systems designed for high voltage test applications do not require separate exciter transformers. The magnetic portion of the circuit is essentially a variable gap transformer, that when connected to suitable capacitive load within the specified load tuning range opf the system

 

[HVTS__1]

Power frequency Parallel Resonant Test Systems designed for high voltage test applications do not absolutely require separate exciter transformers. The magnetic portion of the circuit is essentially a variable gap transformer, that when connected to suitable capacitive load (i.e. the Device Under Test) within the specified load tuning range of the system, provides compensation for the source current and power required from the mains during the tests.
Separate exciter transformers can provide additional functionality to the overall system in many applications. Due to the nature of a variable gap transformer, electrostatic shields used to decouple noise from the mains are not suitable (partial discharge testing). Also, any insulation failures between the LV and HV windings of the transformer are immediately coupled directly to the mains. As many of these systems are designed for mobile use and subjected to harsh environmental and testing scenarios, any protective measures designed to provide the maximum safety of all personnel and connected equipment is paramount. A properly designed separate exciter can provide significant additional safety levels.
A separate exciter provides the ability to "separate" the power ground from the high voltage test ground. Transient currents and voltages are present during any load failure (always expected) and the ability to control these transients and protect adjacent circuits is imperative.
Additionally, a separate exciter transformer allows for the ability to reconnect the system as a Series Resonant test system and realize all of the advantages this test circuit provides. Having an integrated "exciter winding" as a portion of the variable gap transformer "Parallel Resonant" test system precludes this flexibility.

 

[VLFit]

Thank you HVTS_1. That was a great answer. I kind of figured it wasn't needed but prudent for the reasons you stated. Your confirmation is very helpful.
I see you left your web address. I know your company and will contact you outside of this forum.
Thanks again.