The Hi-Lo-Hi approach
For medium-voltage variable-torque applications, a competitive Danfoss solution can be proposed with a Hi-Lo-Hi approach. The medium-voltage incoming power is stepped-down to a low voltage compatible with a VLT® drive. After the power is processed through the drive and passed through a sine-wave filter, it is then stepped-up to the higher voltage via a step-up transformer as required by the motor.
VLT® operation of 3300 V motor
South Korea has recently reported a major application case story involving the use of high-power drives in a Hi-Lo-Hi configuration. A VLT® 6000 has been engineered into a medium voltage drive system to supply variable-frequency power to a 250 kW, 3300 V Motor. Two 250 kW, 460 volt, integrated VLT® drive panels with matching output sinewave/LC filters were delivered. The variable speed application is for an induced draft fan on an industrial waste incinerator.
Compact dimensions, high efficiency and user friendly
The order was secured from Green Solutions Co. Ltd. (GREENSCO), which specializes in industrial waste incineration. Danfoss won against stiff competition and the customer selected Danfoss drives for their compact dimensions, high efficiency and user friendly operator interface.
Break down is life-threatening
During a recent visit to the customer’s site by Park Barb (Director of MC Sales - South Korea), the Technical Director of GREENSCO expressed his satisfaction at the trouble-free operation of the VLT® drives. The VLT® system has resulted in reduced starting power, high energy efficiency, and lower mechanical maintenance. Above all, equipment reliability is a key performance parameter for the application. The drive performance and reliability is critical to the operation of the plant, since any breakdown will lead to the emission of dioxin, a toxic chemical which is extremely harmful to the human body.
Emissions of this toxic chemical are monitored online by the government and strict penalties imposed for non-compliance with the norms. Since reliability is so important, the customer purchased a second standby drive to ensure uninterrupted operation of the incinerator plant. The Hi-Lo-Hi solution from Danfoss has delivered the reliability and performance demanded by the customer.
The drives have been in operation since July 2005. With the installation of the VLT® frequency converter, power consumption has been reduced by 50% and the customer has recovered his investment within one year.
