Product Details – 130B1027 AHF-DA-010-400-50-20-A The Danfoss Advanced Harmonic Filter is a passive harmonic filter specially designed to match the Danfoss VLT AutomationDrive, VLT AQUA Drive and VLT HVAC Drive frequency converters. With AHF 010 connected in front of the Danfoss VLT, the harmonic current distortion generated back to the mains is reduced to 0.1 total harmonic current distortion at full load. Accessories: NEMA 1/IP21 upgrade kit for IP20 units: IP21 / NEMA 1 Kit for AHF X1 enclosure - 130B3274 NEMA 1/IP21 upgrade kit for IP20 units with capacitor disconnect: IP21 / NEMA 1 Kit for AHF X1 enclosure and contactor CI 9 - 130B5903 Back plate: Back plate for X1 - 130B3283