General Description - Megger BM15 Mode D'emploi

GENERAL DESCRIPTION

BM15, and MJ15 testers are completely self contained instruments designed
for high voltage insulation resistance testing in the maintenance and servicing
of rotating plant machinery, transformers, switchgear and industrial
installations.
Tests can be performed at 500 V , 1000V , 2500 V or 5000 V . Insulation measuring
range is 100 kΩ to 20 GΩ and Infinity. Automatic discharge for capacitive
circuits under test is provided and decaying voltage displayed.
A guard terminal can be used to minimise the effects of surface leakage when
carrying out insulation resistance tests.
Tests are initiated by pressing the BM15 'Test' button (or by turning the MJ15
generator handle). Releasing the 'Test' button (or ceasing handle rotation)
causes the instrument to default to ac/dc voltmeter mode, with a discharge
resistor internally connected across the terminals. This feature will give
decaying voltage indication following the testing of equipment possessing
capacitance.
The moving coil meter operates a black pointer to display the readings on a
single logarithmic black scale on a white scale-plate for clarity of reading. The
movement is resiliently mounted for field use.
A slide - in 'Pass Band' overlay can be inserted over the display. Appropriate
Pass/Fail bands can be marked on these windows with a permanent marker for
'Go / No Go' testing.
BM15 is powered by eight 1,5 V (IEC LR6) cells.
Normal power for the MJ15 is by low voltage, hand cranked, brushless a.c
generator. Fitting the battery container supplied, with eight 1,5 V IEC LR6 cells
gives the instrument a dual (independent) supply capability. Both instruments
are fitted with a battery check range, operated by pressing the 'Test' push
button. Cranking the handle too slowly (<180 RPM) results in an unstable
4
pointer reading. Excess handle speed cannot harm the instrument as the
output voltage is electronically regulated.
The case is robust, yet light-weight, made from a flame retardant ABS, with a
polycarbonate display window. Mounted on top of the case is a 6 position,
rotary, range selection switch and a 'Test' push button.
Three recessed sockets are provided, and marked '+', '-' and 'G'. These have
safety covers which open when the plugs are inserted. When inserted into the
sockets, the shrouded test lead plugs lock into position. They are released by
twisting the plug a quarter turn and pulling out.
For this reason, only the test leads supplied or suitable Megger replacement
ones should be used.
Design safety features include:
External voltage, a.c. or d.c., displayed.
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Load automatically discharged at the end of a test, and decaying
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voltage displayed.
Test leads can lock into the case to prevent accidental disconnection.
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