Braking unit for a 400 V DC bus — what the ratings mean
The VW3A7204: This is a network braking unit rated for 33 kW peak braking power and 21.5 kW continuous dissipation on a 400 V supply bus. The 33 kW figure is the short-term overload ceiling — the unit can sink that much regenerative energy from a decelerating motor before the internal resistor string reaches its thermal limit. Efficiency is listed at 97 % with a cos phi of 1 — that is the power factor at the input terminals when the braking IGBT is conducting. The near-unity power factor means the unit draws purely resistive current from the DC bus during braking events, which keeps the upstream drive's DC-bus capacitors from seeing reactive circulating current on top of the braking energy.
Altitude derating and enclosure fit
Above that, the continuous braking current must be reduced by 5 % per additional 1000 m — at 4000 m the unit is running at 85 % of its sea-level rating. The derating is driven by the reduced air density's ability to cool the braking resistor bank, not by the IGBT junction temperature. Mount it inside a panel with at least the clearance specified in the product manual for the 580 mm height, 270 mm width, and 295 mm depth. The associated upstream fuse is rated 80 A at 690 V — this is the short-circuit protection rating, not the continuous current draw.
Obsolete — sourcing through independent channels
Schneider Electric lists this part as obsolete. No official successor part number is published. The unit is available through independent surplus and broker channels — quantities are lot-specific and confirmed at the time of RFQ. A buyer holding a BOM position for this braking unit should verify the remaining stock depth before committing to a long-term maintenance plan. Storage temperature range is -25 to 55 °C, so the unit can sit in a spares locker in an unheated warehouse through most climates. The operating altitude envelope and the 400 V nominal supply voltage are the two parameters that gate the fit — confirm the DC bus voltage of the host drive matches the 380-415 V input limits before ordering.