Braking unit for Altivar 61/71 drives
The VW3A7E101 is a resistance braking unit sized for Altivar 61 and 71 variable speed drives up to 200 kW continuous motor power. It shunts excess regenerative energy from the DC bus into an external resistor bank, keeping the bus voltage from climbing past the drive's trip threshold during deceleration or overhauling loads. Maximum permanent braking power is 420 kW at 400 V, with a 785 V DC +/- 1 % activation threshold. The unit's load factor varies with the braking duty: 15 % at 320 kW, 50 % at 250 kW, and 5 % at 420 kW — these are the engage-threshold figures that govern how long the resistor can absorb power before cooling off.
Thermal and electrical limits
The unit dissipates 550 W of thermal losses internally, and requires 100 m³/h of cooling air volume to stay within the -10 to 50 °C operating ambient range. The maximum DC bus voltage it can handle is 850 V, and the minimum external resistor value to associate is 1.05 Ohm — pair a resistor below this floor and the braking chopper draws more current than the IGBTs can switch safely. Pollution degree 2 per EN 50178 (non-conductive pollution only, occasional condensation) and Class 3K3 relative humidity without condensation. Operating altitude is limited to 2000 m; above that, the air density drops and the cooling capacity falls off, so derate the braking power or add forced ventilation.
Obsolete — sourcing through independent channels
Schneider Electric lists the VW3A7E101 as obsolete. The braking unit is available through independent surplus and broker channels — quantities are lot-specific, and pricing is confirmed at RFQ against your BOM quantity. For a line-down situation, the unit's 785 V DC activation threshold and 1.05 Ohm minimum resistor value are the critical fit parameters. Any replacement braking unit — whether a new-old-stock VW3A7E101 or a functional equivalent from another supplier — must match these to avoid nuisance overvoltage trips or blown chopper transistors.