Weco SKT50-S50kW three-phase string inverter, 4 MPPT

Overview

The SKT50-S is the 50kW model of the STK commercial range and the only one with four MPP trackers: 32A on three of them and 40A on the fourth, two strings each. It accepts up to 75kWp of PV and delivers up to 55.6kVA, with 97.9% European efficiency. RS485 is standard, with Wi-Fi, GPRS or LAN as options, and the IP66 housing weighs 36kg.

• 30, 40 and 50kW, 400V three-phase
• 3 MPPT (30 and 40kW), 4 MPPT (50kW)
• 1100V max., 180–1000V MPPT range
• Type II surge protection on DC and AC
• Optional string monitoring and PID recovery
• IP66, 36kg

How it works

These transformerless inverters feed commercial PV arrays into a 380/400/415V three-phase grid. The SKT30-S and SKT40-S have three MPP trackers with 32A, 32A and 40A input current; the SKT50-S has four, with 32A, 32A, 32A and 40A. Each tracker takes two strings, short-circuit current is 45A or 50A, and the MPPT range is 180–1000V with 200V start-up and 1100V maximum input.

PV array power can reach 150% of the AC rating. Maximum apparent power is 33.4kVA, 44.5kVA and 55.6kVA, with output currents of 3×51A, 3×67.5A and 3×84.3A. Power factor is above 0.99 at rated power and adjustable from 0.8 leading to 0.8 lagging; THDi is 3% at rated power and DC injection stays below 0.5% of rated current.

Key features

European efficiency is 98.0% on the 30 and 40kW models and 97.9% on the 50kW, with maximum efficiency of 98.5% and 98.6% on the 30 and 40kW. Type II surge arresters on both DC and AC, a DC switch, anti-islanding, insulation monitoring and leakage current protection are standard; string monitoring and PID recovery are available as options.

Installation and compatibility

All three models share a 635×530×224mm, 36kg IP66 housing with forced-air cooling, −25 to +60°C operating range and 4000m altitude; night consumption is below 10W. The grid code list covers VDE-AR-N 4105, EN 50549-1, CEI 0-21 and CEI 0-16, UNE 206006/206007-1, RD 1699/661 and 413 and IEC 61727/62116, with IEC 62109-1/-2 for safety. WeCo publishes the datasheet in Italian.

Monitoring and settings

RS485 is standard, with Wi-Fi, GPRS or LAN modules as options for remote access. The inverters show their operating status on LEDs and an LCD and connect to the WeCo app, which displays performance and energy data in real time. WeCo gives a five-year warranty on the series.

Questions and answers