2
Function
2.1
Features
• ISOMETER® for IT AC systems (IT = unearthed electrical systems)
• Two separately adjustable response ranges of 2 kΩ ... 1 MΩ each (Alarm 1, Alarm 2)
• Two-line LC display
• Connection monitoring of the measuring leads to the IT system and to earth
• Automatic device self test
• Option „W“ provides increased shock and vibration resistance for use in ships, in rolling
stock and in seismic regions
• ISOMETER® for IT AC systems with galvanically connected rectifiers and for IT DC systems
U
n
up to 793 V
• Automatic adaptation to the existing system leakage capacitance
C
e
up to 100 μF
• AMP measuring principle (European Patent: EP 0 654 673 B1)
2.2
Product description
The ISOMETER® IR1575H monitors the insulation resistance of IT systems. The IR1575H is designed
for use in 3(N)AC, AC and DC systems. AC systems may include extensive DC-supplied loads (such
as converters). The adaptation to the existing system leakage capacitances takes place
automatically.
2.3
Function
The device is connected between the unearthed system and the protective 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).
The IR1575H superimposes a microprocessor-controlled pulsating AC measuring voltage on the
system being monitored (AMP measuring principle). The „adaptive measuring pulse“, is a measu-
ring method developed and patented by Bender (European Patent: EP 0 654 673 B1). The
measuring pulse consists of positive and negative cycles of the same amplitude. The period
depends on the respective system leakage capacitances and the insulation resistance of the
system to be monitored.
An insulation fault between system and earth closes the measuring circuit. The evaluation circuit
calculates the insulation resistance which is indicated on the LC display or the external kΩ
measuring instrument after the measuring time has expired.
The measuring time is determined by the system leakage capacitance, the insulation resistance
and the system-related disturbances. System leakage capacitances do not influence the
measuring accuracy.
If the reading is below the selected response values ALARM1/ALARM2, the associated alarm relays
respond and the alarm LEDs „ALARM1/2“ light up and the LC display indicates the measured
value (in the event of DC insulation faults, the faulty system conductor will be indicated on the LC
display). If the terminals R1/R2 are bridged (external RESET button [N/C contact] or wire jumper),
the fault message will be stored.
8
IR1575H_D00416_00_M_XXEN / 03.2021
Function
