What is a Variable Frequency Drive (VFD)?
A Variable Frequency Drive (VFD) is an electronic device that controls the speed of electric motors by varying the frequency of the supplied electricity. Instead of operating at full speed or complete stop, the motor runs at the speed the load actually needs.
The Affinity Laws for Pumps and Fans
The key point in energy savings: According to the affinity laws:
- Flow is proportional to speed:
Q ∝ N - Pressure is proportional to the square of speed:
H ∝ N² - Power consumption is proportional to the cube of speed:
P ∝ N³
This means: 20% speed reduction → 49% energy savings! 50% reduction → 87.5% savings!
Applications in MEP Projects
| Application | Expected Energy Savings | Note |
|---|---|---|
| AHU fans (HVAC) | 40 – 60% | Constant pressure control |
| Chilled water pumps | 30 – 50% | ΔP control |
| Cooling towers | 25 – 40% | Temperature control |
| General water pumps | 30 – 45% | Constant pressure control |
