Baker D30R, User'S Manual & Operating Instructions

Page: 58 / 142

D30R Users Manual
58
Do Not Touch Test Leads while test is in Progress!
71-023 Rev C 5/8/2007
The HiPot Over Current Trip Indicator
The Digital tester is equipped with an Auto-Ranging HiPot Over-Current safety
trip. If the HiPot current levels exceed:
•
~900uA in the 100uA/div range,
•
~90uA in the 10uA/div range,
•
~9uA in the 1uA/div range or
•
~0.9uA in the 0.1uA/div range
The over-current trip will remove the high voltage from the test leads, stop the
test and illuminate the red HIPOT TRIP lamp on the front panel. Releasing the
TEST button resets the trip circuitry, extinguishes the red HIPOT TRIP lamp,
and readies the tester for another test.
Effects of Temperature
Temperature has a very strong effect on megohm readings because insulation
resistance varies inversely with temperature on an exponential basis. (IEEE 43
has a very good description of this effect.)
Simply put, the insulation resistance drops in half for every 10
o
C rise in
temperature. Therefore, before any judgments are made regarding the health of a
motor’s insulation based on a trend of past megohm measurements, all the
measurements used in the trend should be “compensated” or “corrected” for
temperature. The temperature compensation of the insulation resistance means
to convert all the IR measurements used in the analysis to the same temperature.
The recommended temperature to use is 40
o
C. The following formula should be
used to make the calculation.
( ) (
)
R R
T c
T
∗
⎥
⎦
⎤
⎢
⎣
⎡
⎭
⎬
⎫
⎩
⎨
⎧
−
∧ =
10
40
2 / 1
For example: An insulation resistance/megohm value is 5000Mohms at 30
o
C,
the compensated IR value at 40
o
C is 2500Mohms.