Braking unit for Altivar 61/71 — what it handles
The VW3A7E103 is a resistance braking unit designed for Schneider Altivar 61 and 71 variable speed drives up to 300 kW continuous power. It shunts regenerative energy from the DC bus into an external resistor bank when the motor decelerates or holds a load, preventing DC bus overvoltage trips. Peak braking power is 450 kW at 690 V, but the load factor thresholds tell you how long you can stay there: 15 % at 400 kW, 5 % at 450 kW, and 50 % at 350 kW. That means at full 450 kW peak you're limited to a 5 % duty cycle — about 3 seconds of braking every minute — before the unit needs to cool. At 350 kW you get a 50 % duty cycle, which suits applications with longer, lower-torque deceleration. The DC bus activation threshold is 1075 V DC ± 1 %, and the maximum DC bus voltage is 1100 V. The minimum external resistor value is 2 Ohm — going lower risks overcurrent through the IGBT chopper. Thermal losses are 650 W, which means the cabinet needs to shed that heat continuously during braking events.
Installation constraints and environment
The unit requires 600 m³/h of cooling air — that's a forced ventilation fan in the cabinet, not passive convection. Mount vertically only; horizontal install blocks the airflow path. Pollution degree 2 per EN 50178 means it's suitable for a normal industrial environment with non-conductive dust, but not for wet or conductive contamination. Relative humidity class 3K3 without condensation. Altitude derating applies above 1000 m: reduce ratings by 1 % per 100 m up to 2260 m. Vibration resistance is 0.2 gn — avoid mounting directly on a machine frame without isolation. Integrated thermal protection via a thermal probe in the resistor path prevents the braking circuit from cooking itself if the duty cycle is exceeded. This isn't a fuse — it's a sensor that signals the drive to stop braking before the resistor overheats.
Obsolete — sourcing the VW3A7E103 today
Schneider has marked the VW3A7E103 as obsolete. There is no official pin-compatible successor from Schneider for the Altivar 61/71 braking unit line. If you're keeping an Altivar 61 or 71 on life support, this is the braking unit you need, and it's only available through independent surplus or new-old-stock channels. Lot-specific units from traceable industrial surplus. No stock-holding claim; every order is a confirmed procurement run.