Schwarzbeck NNHV 8123 Single Path High Voltage AMN (LISN)

The main application of the unsymmetrical single path AMN (artificial mains network) NNHV 8123 is the measurement of interference voltage for electromobility purposes according to CISPR 25 edition 4 or BMW GS 95025-1 in the HF-VHF range 0.1 MHz – 150 MHz utilizing shielded cables. It can also be used for BCI tests using an external 50 ? termination.

The impedance characteristics are basically realized by connecting an inductor in parallel with the input impedance of the measurement receiver: 5 µH || 50 ?.

The LISN has been designed to be installed into a shielded housing HVSE 8600 in pairs. Each NNHV 8123 can be used to measure one single path. To be able to measure HV+ and HV- 2 units are required. The device under test has to be connected to the terminal at the front panel. The supply voltage has to be connected at the back panel. The shield is connected to the HVSE 8600 feedthrough.

The device under test may drain a continuous current of 70 A and for a short period of time it may even drain more than 100 A.

Interference voltage measurements acc. to CISPR 25

Mains is connected at the back side. The 0.1 µF capacitor located at the backside is connected to ground. The device under test has to be connected to the front panel. The RF-interference voltage emitted by the equipment under test can be measured at the N-connector using an EMI receiver.

One LISN (that fits into a shielding enclosure HVSE 8600) has to be used for each path. The supply line has to be connected to the red terminal of one LISN and the return line has to be connected to the red terminal of the other LISN. The measurement port that is not being used at the moment has to be terminated with 50 ?.

The RF-ground of both LISNs has to be connected to the GND-terminals. The GND connection with the massive brass wing terminals provides the mechanical and electrical connection to the housing HVSE 8600. To connect the inner conductor of the shielded cables with the red terminal of NNHV 8123 it is required to duct it through the outer housing at first. When the cable end is inside the housing the screw terminals are attached and the cables can be connected to NNHV 8123. Two pieces of screw terminals are within the scope of delivery of the NNHV 8123 series. The short RF-cables to connect the measurement outputs with the housing are within the scope of delivery of the shielded enclosure HVSE 8600.

Immunity tests with bulk current injection (BCI-tests):

The NNHV 8123 can be used for bulk current injection tests using suitable current injection clamps.

A sufficient air-circulation must be provided to avoid overheating of the LISN. Do not cover the LISN! The top and bottom hole-plates must not be covered to provide good air circulation. The external 50 ? dummy load must be placed outside of the HVSE 8600 allowing good air circulation.

A light smell of coating and insulating material may appear in the first hours of operation, take care for not inhaling the emitted gas. The smell will disappear after some hours of operation at high temperature.

During bulk current injection tests danger may arise by high field strengths and temperatures (fire hazard!), therefore these tests must be performed by qualified personnel only! The relevant safety precautions must be considered!

The power injected at the EuT-terminals is being converted to heat inside the external 50 ? terminating resistor. Please choose the power rating of the resistor according to the expected maximum of the RF-power!

Please note: The injected RF-power passes from the EuT-terminals directly to the Nconnector without any attenuation. Eventually connected RF-measuring equipment may be damaged

Notice: As the circuitry is according to CISPR 16 there are high ground currents. It is normally not possible to use a LISN on power lines with ground current safety switches (They disconnect power due to excessive ground current). Either a special power line outlet without ground current safety switch must be installed (warning label required!), or an isolating power line transformer 1:1 must be used.

In any case, ground-connect LISN before connecting to power line. Precise safety instructions must be provided to any user of the LISN.

Differences to the NNBM 8124 series:

The NNHV 8123 is used for measurements on shielded DuTs in the automotive industry. Low voltage DuTs which are connected with unshielded cables are measured with the NNBM 8124 series. Both types use a 5 µH inductor and the same diameter and distance of the terminals and the same housings. Existing calibration adapters can be used for both types of AMN - LV and HV. The circuitry is different at the input where the NNHV 8123 uses only 0.1 µF whilst the NNBM 8124 series uses 1 µF capacitors. Thus leaking currents to ground are lower in case of the NNHV 8123.

The NNHV 8123 series has no built in switchable termination as the NNBM 8124 series does. The immense heat dissipation caused by BCI testing can be kept outside the shielded housing in that way. The terminals of NNHV 8123 have no threads. They consist of multiple parts to provide a possibility to duct the cables through the housing. The NNBM 8124 uses wing terminals.

NNBM 8124 is usually not put into a shielded housing whilst the NNHV 8123 must be installed in pairs in the shielded housing NNHV 8600 to simulate the properties of shielded HV-networks in EV or HEV.