HV Transformer
The HV transformer is a completely dry resin encapsulated
transformer with two HV terminals with moulded saddles. The midpoint
of the transformer HV winding is earthed so that the voltage of
each terminal to earth is only half the test voltage.
Safety
Maximum possible safety of the operator as well
as the equipment is ensured by a safety conscious design. The output
controller is interlocked at its minimum position so that HV can
be switched ON only when the voltage controller is at zero and the
hood is shut. The output controller must be brought to zero after
every test or interruption. The hood leading to HV terminals has
a safety switch fitted so that opening of the hood shuts the HV
OFF.
Cabinet
Portable, powder coated, sheet steel with lifting
handles.
Test Cell model TC-2
The test cell with cover is made of Methyle Methacrylate
(Arcylic) having effective oil volume between 300 to 500ml with
adjustable and removable 36mm mushroom head electrodes to IS 6792
and IEC 156 along with electrode gap distance GO & NOGO gauges,
made of alloy steel, precision ground and hardened.
Optional
Test Cell with suitable electrode spacing gauges:
1. Type TC-1: Same as TC-2 but with 12.5
to 13mm spherical electrodes.
2. Type TC-3: Same as TC-2 but with 1"
dia flat disc electrodes to ASTM D 877.
Standard Accessories
1. Mains cord, 2 meter long.
2. Test cell TC-2 with electrodes.
3. GO & NOGO gauges.
4. Operating Manual.
Operation
All the controls and indicators are located on
a top panel with clear and easy to understand legends. A kV meter
indicates the value of the test voltage and following breakdown
of the test sample, continues to indicate the breakdown voltage
after the circuit breaker has tripped and removed the test voltage.
Motor may be stopped and re-started as required
so that it is possible to hold any test voltage desired (upto maximum)
constant for a period of time. The circuit breaker ignores transient
spark-overs in the oil sample.
Circuitry
The mains is applied to a continuously variable
torodial auto transformer through a switch and fuse. The output
of this variable auto-transformer is fed to the primary of the HV
transformer. The secondary of the HV transformer has its midpoint
connected to the earth through a current transformer. The secondary
of the current transformer is connected to a sensitive relay. When
the leakage current in the circuit exceeds a pre-set value, the
relay operates, thereby tripping the supply to the primary of the
HV transformer. |
