1.1 Design and Function:

The PGK HB instruments are designed as two-part High Voltage Testing Sets.

• Operating unit with all indicating/operating elements, with power supply and safety

devices.

• High Voltage unit as oil-filled housing with High Voltage transformer with the choice of a

rectifier bar for half-wave rectification or a resistance bar as a damping resistor.

With the PGK 70 - 2,5 HB, PGK 110 HB, PGK 150 HB and the PGK 260 the

corona protection hood is used as oil expansion tank (conservator) and may not be

removed or damaged. With the PGK 70 HB an air cushion in the housing (tube)

works as a compressible volume for absorbing the oil expansion. That.s why the

H.V. unit may only be stored, shipped and operated vertically.

High Voltage generation

Generation of high voltage is carried out by a H.V. transformer supplied by an

variable transformer. During D.C. operation a half wave rectifier is connected after

the H.V. transformer. By turning the half-wave rectifier the polarity of the output

voltage can be changed. The capacity of the test object acts as smoothing

capacitor. During A.C. operation, a damping resistor is connected to the H.V.

circuit instead of the half-wave rectifier (with PGK 260 HB: option - not included)

The H.V. units of the PGK HB instruments are equipped with a potential grading

ring which can also be used as carrying ring. The instruments may be not operated

without this potential grading ring.

Operating ranges:

Depending on the load by the test object and the voltage set, the PGK HB

instruments are operating in one of the two operating ranges Continuous

Operation and Short-time Operation.

Continuous operation:

Within this operating range, from no-load to nominal rating up to cut off load the

instrument can be loaded continuously.

Short-time operation:

Within this operating range from cut off load to short circuit the instrument

switches current-limiting lamps into the primary circuit of the H.V. transformer in

order to reduce the thermal load of the instrument. Additionally, as a protection

against overload the over current protection switch (5) with its thermal and

magnetic tripping characteristic is tripped after a specific period terminating

operation. The time until tripping depends on load and takes from seconds (during

short-circuit) to hours (at maximum load).