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 at this power range is 4500 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 0.30% 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.

Danfoss now expands its range of VLT® drives with power capabilities all the way up to 1.2 MW. Drive voltage ratings range from 380VAC through 690VAC. The unique “back-channel” is extended through the entire range of drives.

Heat losses minimised
The overall electronic design of VLT® Drives together with the use of high quality electronic components is the basis for unsurpassed energy efficiency. Once heat losses in the electronics are limited, also the energy used to operate the cooling can be limited.
This way VLT® high power drives end up loosing only 2% of the provided energy as heat. The rest is utilised in the application.

Exceptional cooling concept
The VLT® high power drives all have their energy efficient power transistors mounted up against the effective aluminium or copper heat sinks, which at the same time effectively separates cooling air and heat gain from the electronics.
With this principle, it’s possible to force cold air through the cooling duct without polluting the electronics with dust and other residues from the ambient air.
Once controlled, the cooling air stream can be ducted directly outside the cabinet – or outside the building.

The back-channel cooling system is standard on Danfoss high power drives whether you choose IP00, IP21 or IP54 enclosures. With the addition of optional duct kits the back-channel cooling can be extended to standard industrial enclosures where the drives are installed. These thermally tested kits ensure the most efficient cooling of the drive while maintaining the protection rating of the industrial enclosure.

Durable
As an option, the back channel cooling duct work and heat sinks can be ordered with corrosion protection for installations in harsh environments – salt-air environments near the ocean an example.

Fitted standard equipment
Danfoss has elaborated on the cooling concept and now provides IP00 chassis mount drives and dedicated duct kits, fitted for mounting the high power drives in standard industrial cabinets such as the Rittal TS8 Series, which makes commissioning extremely easy.
With the kit, the built in fans of the drive takes in cooling air from outside the cabinet, through the heat sink, and out from the top of the cabinet.
Mounted inside the cabinet, the drive is well protected. A remote mounting kit is provided to place the local control panel of the drive on the front of the cabinet, so the drive can be operated without opening the cabinet.

Save space
The compact design of the VLT® drives - and high power drives in particular - makes them easy to fit in even small installation spaces. Built-in RFI filters, fuses and disconnects in enclosure options – including IP00, IP21 and IP54 - facilitate this compact installation.
The need for external AC coils is eliminated by the built-in DC coils for harmonic suppression.

Front access
Along with the compact size of the drives, installation space requirements can be further reduced by mounting the drives side-by-side with zero clearance. The drives are designed for easy maintenance and serviceability with easy access to all components of the drive from the front.

Makes motors efficient too
The VLT® feature Automatic Energy Optimisation vector technology ensures maximum magnetification of the motor, minimizing passive, damaging currents and flux in the motor.
This means that maximum electrical power provided the drive is exploited in the application.

On a six meter wall you can place 10 drives providing 6.3 MW (at 690V) or 4.5 MW (at 400V)

The process heat from these drives is 126/90 kW. But mounted on an outside wall, leading the heat sink cooling air directly outside, only 19/13.5 kW disposed inside the room.

The most powerful VLT® drives from Danfoss with power capabilities all the way up to 1.2 MW. Drive voltage ratings range from 380VAC through 690VAC.

Email: sara.bernard@danfoss.com