Variable Speed Drives In HVAC Applications - No Longer An Afterthought!
What are variable speed drives (VSDs, or variable frequency drives)?
SDs are electronic devices that allow you to control an electric motor to precisely match its process requirement. In HVAC systems, centrifugal pumps and fans use variable-torque load motors that can greatly benefit from this technology.
- VSDs allow you to optimize a motor's torque, horsepower and current draw. For example, instead of regulating the flow of air from a fan using a damper (very inefficient), a VSD allows you to control airflow by directly controlling fan motor speed (very efficient).
- VSDs soft start electric motors by gradually bringing a motor up to speed, unlike single-speed starting, which requires up to ten times full-load current. Frequent peak electric surges to start motors result in electromagnetic and heat stresses in motors, and pumps and pipes are subject to hydraulic and mechanical stresses. VSDs therefore extend the life of electric motors, fans and pumps and reduce their maintenance requirements.
- VSDs also reduce voltage sag on power grids as motors come up to speed and negatively affect other motors on the network. Using VSDs means you draw much less peak current, making more efficient use of the motors you have.
- The slower a motor needs to turn, the less power it requires. A motor controlled by a VSD will consume 25% as much electricity if it runs at 50% of maximum speed than if it runs at 100% velocity.
- Two of the most common electrical devices used in HVAC installations are variable-torque centrifugal fans and pumps. They also happen to be some of the highest energy-consumers on the planet. The time is now to move into a new era of energy efficiency with VSDs to reduce wasteful energy consumption and long-term costs.
Short-term advantages of VSDs
- Small size with hinged covers offer easy access and make for painless installation in new set-ups and retrofits
- VSD units are highly modular and therefore easily adaptable to specific equipment requirements
- Programmable integrated software allows VSDs to be adapted to needs of existing and future installations
Long-term advantages of VSDs
- Lower electricity consumption and operating cost
- Extended equipment life and reduced maintenance