Braking unit for Altivar 61/71 — 900 kW peak at 690 V
The VW3A7E104 is a resistance braking unit designed to mate with Schneider Altivar 61 and 71 variable speed drives rated up to 400 kW continuous. It shunts regenerative energy from the DC bus into an external resistor bank when the bus voltage exceeds the activation threshold of 1075 VDC ± 1 %, preventing overvoltage trips on overhauling loads. Maximum permanent braking power is 900 kW at 690 V under constant power conditions at the engage threshold. The unit handles a 50 % load factor at 500 kW, 15 % at 600 kW, and 5 % at 900 kW — these duty cycles define how long the braking transistor can conduct before the thermal budget is exhausted.
Thermal management and integration constraints
Dissipates 1150 W internally as heat — that loss must be exhausted from the enclosure. Requires 600 m³/h of forced cooling air, so a panel fan or dedicated ventilation path is mandatory; natural convection alone will not clear the thermal load at rated duty. The minimum external resistor value is 1 Ohm. Operating altitude range is 1000 to 2260 m with a 1 % derating per 100 m above 1000 m. Pollution degree 2 per EN 50178 applies — the unit expects a clean, dry environment typical of a ventilated industrial control cabinet. Mounts vertically only. Vibration resistance is 0.2 gn — adequate for fixed floor-mounted panels but not for machine-mounted or mobile applications without additional damping.
Obsolete — sourced through independent channels
Schneider has classified the VW3A7E104 as obsolete. No direct factory replacement or successor order code is published for this braking unit. For existing Altivar 61/71 installations that need a drop-in spare, the only channel is the independent surplus and broker market.