Danfoss VLT 12-Pulse Drive Overview

Were Jeremy Clarkson to pen this review, he would no doubt tell you the 12-Pulse Drive is… a very serious piece of kit. Essentially a high efficiency variable frequency converter, like all Danfoss drives in the range it is extremely durable and very cost effective, whilst also providing for an extremely robust and dependable drive.

12 pusle driveFor the more demanding industry solutions requiring over 250 kW of power, the 12-Pulse drive may well be the best option. And in terms of marrying the twin requirements of economy of price, and reliability of function, it really can’t be beat.

Evolved Functionality

The VLT 6-pulse drive remains one of the most popular in the Danfoss range. So you’ll be pleased to here than its 12-Pulse big brother is constructed using the same, much loved modular design.

Essentially, the Danfoss VLT 12-Pulse Drive operates as a high efficiency variable frequency converter, providing harmonic reduction without any additional capacitive or inductive components. Such components can often cause system resonance problems, necessitating further network analysis.

Working within ideal grid conditions, the 12-Pulse eliminates the 5th, 7th, 17th and 19th harmonics. Using a 30°-phase shifting transformer, the net result is a THiD registering at about 12% at full load.

So, no special controls are needed. The drive will simply provide for harmonic current reduction, natural harmonic cancellation and input transient immunity. Efficient (with DC link inductors); easy to commission (with standard LCP and programming); and easy to maintain (because of the modular nature of the design), the 12-Pulse is reliable and stable in all operating conditions.

A compact drive, zero clearance mounting means you won’t lose much floor space. The drive therefore provides the perfect solution where applications require isolation from the grid, or else require a step down from medium voltage.

Reliable and versatile

The 12-Pulse’s PC software and user interface offer functions for everything from commission data and event logging, network monitoring and measuring, filter load and status and for software updating, as well as many more.

LCP Regulations have been considered, and the drive will work up to 3280 feet above sea level, and an ambient temperature of -10° C to +45° C. In effect, it’s a reliable workhorse in pretty much all conditions.

Quality Danfoss Performance

The 12-Pulse operates between 250 kW-1.2 MW and 315 kW-1.4 MW (FC 302 and FC 102/FC 202, respectfully). In terms of the voltage range, the 12-Pulse works between 380-690 Vac and 50-60 Hz.

The enclosure is IP21 / NEMA Type 1 and IP54 / NEMA Type 12 and the drive offers displacement of >0.98 and a True Power factor of >0.98. In the words of Mr Clarkson…. woof WOOF.

12-Pulse Drive Accessories

The 12-Pulse drive is offered with similar drive options and accessories to the 6-Pulse. It can be readily configured dependent on the requirements of the customer and the situation. Class A2 RFI; and Class A1 RFI filtering is optional, as are the power fuses.

Extra Efficiency

The system of cooling through the back channel greatly improves the efficiency of the Danfoss VLT 12-Pulse Drive. The 12-Pulse also meets various technical specifications, including EN50178 and EN60146 for safety and design, EN55011 for electromagnetic compatibility and IEEE587, ANSI C62.41 and EN61000-4-5 for surge immunity.

The drive is also compliant with the EU’s RoHS directive. Brought in in 2006, the Restrictions of Hazardous Substances directive restricts the use of potentially damaging chemicals in electronics manufacture. Danfoss remains proud that its drives are always built with a commitment to the preservation of the environment.


As with all the drives in the series, the 12-Pulse drive combines versatility with durability, creating the perfect solution for situations that necessitate the use of a high frequency converter.