Description / Typical Applications

SNV040EC is a “combiner box” card with dc current, voltage measurement and with three digital inputs. It is designed to be used in photovoltaic parks with central inverters in order to connect in parallel strings and monitor string currents and voltage.

It has specific board shape to fit in DIN rail fuse holders, avoiding extra cabling and material costs. Current collector bar is pre-mounted and designed to be directly connected to the disconnector switch for a more clear and cost efficient installation. Negative pole collector bar can also be provided.

Current measurement is performed on the positive side. Very low thermal drift and thermal stability is achieved due to continually active correction from microcontroller. Measurements are amplified through precision amplifiers and then sampled and processed by a 32bit CORTEX-M3 microcontroller at 96MHz.

The microcontroller can deliver measurements through an isolated serial RS485 bus transceiver using Modbus protocol. It can also hold values, in order to perform simultaneous measurements through all the cards in a bus and then retrieve all the measurements. The microcontroller is also calculating the average of voltage, currents and current square values, with 347Hz sampling for each channel. The averaging period is indicated-marked by a master controller command. Averaged values of different cards are synchronized and then collected. Bandwidth consumption on the bus is limited, giving the ability for a prompt response of the rest requests.

Three contact inputs are also implemented in order to monitor other component like the condition of an SPD, disconnector switch status, etc. Board temperature is also measured and provided.