16
Function
Product description
The IRDH375 A-ISOMETER
®
monitors the insulation resistance of IT systems. It
is suitable for universal use in 3(N)AC, AC/DC and DC systems. AC systems may
include extensive DC supplied loads, such as converters or thyristor-controlled
DC drives (see 2.3). The device automatically adapts itself to the existing system
leakage capacitance.
Suitable coupling devices are available to extend the nominal voltage range.
The IRDH375 A-ISOMETER
®
is fitted into an enclosure for panel mounting
144x72 mm (BxH).
Function
The IRDH375 A-ISOMETER
®
is connected between the unearthed system and the
equipotential conductor (PE).
The response values and other function parameters are set via the function keys.
The parameters are indicated on the LC display and are stored in a non-volatile
memory (EEPROM) after setting.
A microprocessor-controlled pulsating AC measuring voltage is superimposed
on the system (AMP
Plus
measuring principle*). The measuring cycle consists of
positive and negative pulses of the same amplitude. The period depends on
the respective leakage capacitances and the insulation resistance of the system
to be monitored.
An insulation fault between system and earth closes the measuring circuit. An
electronic evaluation circuit calculates the insulation resistance which is indicated
on the LC display or the external kOhm measuring instrument.
The response time depends on the system leakage capacitance, the insulation
resistance, and the system related interference disturbances. System leakage
capacitances do not influence the measuring accuracy.
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