Schwarzbeck PVDC 8301 DC-AMN (LISN)

The symmetric DC-LISN PVDC 8301 can be used for measuring the disturbance voltage in the frequency range from 0.15 MHz to 30 MHz on photovoltaic inverters.

Up to now the conducted emissions of photovoltaic inverters at the mains terminals were usually measured using LISN according to CISPR 16-1- 2. The circuit concepts of PV-inverters may cause ripple currents on the DC-side of the inverter, though. These ripple currents, which mostly are in direct proportion to the mains frequency, are passing through the cabling and the PV-generator modules and can be radiated as magnetic fields with sometimes remarkable disturbance effect. Traditional measurements at the PV-inverters' AC terminals will not be able to reveal such disturbance phenomena.

The PVDC 8301 was especially designed to measure all kinds of disturbance voltages at the DC-side of photovoltaic inverters. These are in detail the disturbance voltage of one conductor above reference ground (unsymmetrical disturbance voltage), the common mode disturbance volage of a pair of conductors above ground (asymmetrical disturbance voltage) and finally, the differential mode voltage between two conductors.

Application

The symmetric DC-LISN PVDC 8301 can be used for measuring the disturbance voltage in the frequency range from 0.15 MHz to 30 MHz on photovoltaic inverters. It is designed with air-core or iron-free inductors to prevent intermodulation. The permitted continuous current is 200 A with activated fans and 100 A without fans. The PVDC 8301 is able to handle 250 A for a short period of time.

The temperature of the built in inductors may not exceed 150°C. The device under test has to be connected to the wing terminals of the front panel. The PVgenerator or the PV-simulator is connected to the rear side.

The capacitor C3 was limited to 0.22 µF to avoid possible interference to the EuT. This leads to a differential mode decoupling of more than 20 dB. If higher decoupling values are required (e.g. 40 dB or more), one can use an additional 0.1 µF / 1500 V DC capacitor at the AE-terminals.

The photovoltaic generator or simulator must be connected to the rear side (AE) of the PVDC 8301. The device under test (EUT) i.e. the DC input of a PV-inverter has to be connected to the terminals at the front panel. The RF interference voltage emitted by the DC-side of the inverter is decoupled at the ‘output’ BNC jack where it can be connected to a 50 Ω EMI receiver. The switch on the front panel must be set to "DM differential mode", "CM common mode", "A", or "B" depending on the desired mode of measurement. Mode A or mode B: The unsymmetrical interference voltage is measured from port "A" or "B" to RF-ground (V-LISN).

Common mode (CM): The sum of interference voltage of port „A“ and „B“ is being measured against RF ground (T-LISN, asymmetrical disturbance voltage).

In these three modes of measurement the input impedance seen from the device under test is 150 Ω. Differential mode (DM): The symmetrical disturbance voltage between the terminals „A“ und „B“ is being measured (Delta LISN). The impedance is 150 Ω in this case.

The RF ground potential is being connected with the GND connector or with the aluminium bars on the rear panel.

Notice: In any case, ground-connect LISN before connecting to power line. Precise safety instructions must be provided to any user of the LISN. Inappropriate usage of the LISN may cause fatal harm!

Always switch off the supply voltage before connecting or disconnecting terminals. An easily accessible circuit breaker before and behind the LISN is stringently required! The capacitors of the LISN can store charge over a long time, even if the LISN is completely disconnected from power supplies and EuT. We strongly recommend to discharge the capacitors using an isolated cable to ground before touching the terminals. The dischargeresistors from “A” or “B” to “GND” are 1.5 MΩ, because the majority of GCPC (Grid Connected Power Conditioner) are testing several isolation conditions during start up.

Air circulation must be possible at any time. Neither the top side nor the bottom side of the LISN may be covered during operation!