Danfoss’s new high power drives set new standards for heat management
Due to Danfoss’ highly effective power modules the VLT® drives are extremely energy efficient. 98% of the power supplied is utilised in the application and only 2 % is lost through the drive system. Despite the small percentage of losses, 2 % of losses for a 450 kW drive is still 9000 W – corresponding to the heat from 150 classic light bulbs. The difference between a 97% efficient drive and a 98% efficient drive in this example is 3000 watts and becomes increasingly more significant as the size is increased. With the increased power density of the Danfoss power sections, and zero-side clearance mounting several drives may be installed in a small control room i.e. 10 - 450kW drives can be installed on a wall space no more than 6 meters. With this compact installation cooling the control room becomes the next issue. Removing 90kW of heat from the control room represents a cooling challenge. Initial cooling equipment costs and energy consumption costs for cooling add significantly to the lifecycle costs of the drive.
A unique “back-channel cooling” system separates the cooling air and helps solve the heat loss problem by taking air from the outside of the control room and exhausting it back outside. The majority of the cooling air and 85% of the heat losses are passed to the outside of the control room reducing cooling costs. Furthermore, this cooling air only passes over heat sink surfaces and is not seen by the internal electronic components of the drive. This keeps a significant amount of contaminants outside of the drive resulting in extended life and reliability.
Heat gain inside the control room is therefore only 0.3 % of the drive power rating, and excess heat from a 450 kW drive will be only 1350 W - corresponding to the heat from only 23 light bulbs.
