HVAC drive aimed at addressing all the requirements for reliable operation

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February 2001 Motion Control & Drives

As a result of Danfoss' extensive experience as a developer, manufacturer and supplier of drives, the interests of individual consumers are considered to the greatest possible extent when designing new products, a fact strongly underlined by many new features in the VLT 6000 HVAC series - dedicated drives for the HVAC market. One of the basic features making the drive an obvious choice for HVAC applications is the flexible product design, comprising two enclosure types.

These are the IP 20 book style for installation in switchgear panels, combining a minimum space requirement with fast and easy installation; and the IP 54 enclosure for direct wall mounting close to the motor. All drives can be installed side by side since no additional room for heat dissipation is needed. A built-in cooling fan allows operation at ambient temperatures up to 45°C in IP 20 and 40°C in IP 54 without derating.

The VLT 6000 HVAC drive has a range of auto-derating features, the purpose of which is to protect the installation while keeping often-critical operations up and running.

The auto derating at excessive temperatures automatically reduces the switching frequency in order to minimise losses. If necessary, the output power is reduced to maintain operation at lower speed, which increases the lifetime of capacitors. The autoramping function prevents the drive from tripping in case the ramp time values are programmed too short, heavily reducing downtime and ensuring reliable starts and stops.

The VLT 6000 HVAC series is equipped with several features protecting drives and motors in often demanding operating conditions common to HVAC environments. These include the sleep mode with boost function, which stops the motor automatically when motor operation is sensed to be unnecessary to satisfy the demand. The purpose of this function is to prevent, for example, pressure booster pumps from running at low speeds without producing pressure (night-time operation). The integrated PID Process Controller respects the minimum and maximum limits of the drive such as the frequency and ramp times, while run permissive is a very useful safety function in HVAC systems. It allows the user to check any pre-run conditions before starting the drive, not least confirming that the dampers have opened to protect the ductwork in fan applications. Included in this feature is the possibility of operating the damper actuator.

The VLT 6000 HVAC drive also offers effective monitoring of outputs. Both relay and digital outputs can be programmed to indicate numerous operating conditions, such as low or high output current and low or high output frequency.

The Flying Start function further contributes to the reliability of the drive by preventing drives from being damaged when they are coupled to a rotating motor. This function synchronises the output of the drive to the motor on any start commands. With these and several other dedicated features of the VLT 6000 series, Danfoss is ready to support safe and reliable operation of any HVAC application.

maddisont@danfoss.co.za

www.danfoss.com

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Motion Control & Drives

HVAC drive aimed at addressing all the requirements for reliable operation

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