Use of Variable Speed Drive in Fans, Pumps and Air Compressor

Variable Speed Drives have become the prominent motor tools when it comes to optimise the speed of HVAC equipment. Variable speed drives are ideal and effective to control the connected load speed, ramping up and down the motor speeds, thereby limiting the energy usage and improving the performance and durability of the equipment.

Owing to this benefit, there are several applications where variable Speed Drives are used typically, as appended below:

1. Fans
   Variable speed drives helps to reduce speed of fan that results in decreased energy consumption, as well as decreased vibration and noise.

   Variable speed drives help to create variable torque characteristic of the fan and the reduction in input power is in cube law relative to the reduction in speed. While damper controls have been other speed reduction method in fans, that led to the decrease in input power with reduced flow rate but lead to noise generation because of damper changing position that creates noise and vibration. This is something variable speed drives are effective at controlling and reducing.

2. Pumps
   In pumps too, the traditional method of using throttle control for maintaining the efficiency does not provide effective results, and is therefore ideally replaced by variable speed drives. With a throttle control, the pump does not run at the design point, which leads to decreased productivity, specifically in applications like geothermal pumps and heating circuits.

   Whereas variable speed drives effectively helps to enhance the control of the motor speed resulting in enhanced efficiency and improved power saving, overall.

3. Air Compressor
   In comparison to the pumps and fans, there is slight degree of change you can achieve when using variable speed drives for controlling the speed as the compressors are constant torque load and pumps and fans are variable torque loads. However there are situations and cases when air compressors remain lightly loaded for long periods of time and there it becomes befitting to fit a variable speed drive. When the compressor is off-load more than it is on-load you can assess the condition to retrofit a variable speed drive.

There are various HVAC equipment whose functioning has been changed and efficiency has been improved using the variable speed drives (VSDs) like water pumping systems, boiler systems and more, across several industries.