Si50-203
Periodic Inspection
Semi-Hermetic Single Screw Compressor Version III
5
3.2
Periodic Inspection Instructions
1. Insulation Resistance of The Motor
!
Insulation Resistance Testing
A megger is used to apply voltage directly to an insulated object, measure leakage current
through the insulated object, and find the insulation resistance values. Its scale is voltage /
leakage graduated with such insulation resistance values.
The following equation holds:
Insulation resistance = applied voltage / leakage current
Note:
1. A megger indicates an increasing resistance value with time, because absorption current
flows through the insulated object at an early stage, lowering the resistance value
correspondingly.
2. Prohibit anyone from measuring insulation resistance in a vacuum.
It must be measured at atmospheric pressure or after the filling of refrigerant. The reason
is that in a vacuum, the insulation ability of gas lowers, and thus electric discharge is apt to
occur.
(
Measuring Procedure
)
(1) Turn off the main power and operating power.
(2) Remove the terminal cover.
(3) Before measurement, disconnect the cables connected to the compressor or control panel.
(4) Disconnect the CTP protector lead wire.
(5) Conduct measurement.
Fig. 3-1 Motor insulation resistance measuring method
(
Measurement Standard
)
Using a 500-V megger. The measured value shall be 3 M
Ω
or higher.
