Schwarzbeck PVDC 8300 DC AMN (LISN)

The symmetric DC-LISN PVDC 8300 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 8300 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.

The conducted emissions of photovoltaic inverters at the mains terminals are 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. These ripple currents 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 PVinverters' AC terminals will not be able to reveal such disturbance phenomena. The PVDC 8300 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 voltage 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 8300 can be used for measuring of 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 100 A with activated fans. Without fans 50 A continuous current can be supplied. Short time currents over 150 A can be applied. The temperature of the built in inductors may not exceed 150°C. The device under test is connected to the wing terminals of the front panel. The PV-generator or the PV-simulator is connected to the rear side.

The capacitor C3 was limited to 0.22 µF to avoid possible malfunction of 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), the use of an additional 1 µF / 1500 V DC capacitor at the AE-terminals will bring significant improvements.

Interference Voltage measurements

The photovoltaic generator or simulator must be connected to the rear side (AE) of the PVDC 8300. The device under test (EUT) i.e. the DC input of a PV-inverter is connected to the terminals at the front panel. The RF interference voltage emitted by the DC-side of the inverter is measured 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 wished measurement mode.

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 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 measured (Delta LISN). The impedance here is 100 Ω.

The RF ground potential is 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 deadly injuries!

Always switch off supply voltage before connecting or disconnecting terminals. An easily accessible circuit breaker before and behind the LISN is a must! The capacitors of the LISN can store charge over a short time, even if the LISN is completely disconnected from power supplies and EuT. We recommend to discharge the capacitors using an isolated cable to ground before touching the terminals. The discharge-resistors 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!