Selecting the right Variable Frequency Drive (VFD) is crucial for optimizing motor performance and efficiency. But with so many load types and applications, how do you pick the perfect VFD? The answer lies in understanding your load characteristics. Whether it’s a conveyor, fan, or punch press, matching the VFD to the load ensures smooth operation and energy savings. Let’s break it down in simple terms.
Understanding Load Types
Loads aren’t all the same—some need steady torque, while others demand more power at higher speeds. Here’s a quick guide to the five main load categories:
Constant Torque Loads
Torque stays the same, but horsepower changes with speed.
Examples: Conveyors, hoists, mixers.
VFD must deliver high starting torque (1.5x or more) to overcome inertia.
Variable Torque Loads
Torque increases with the square of speed (e.g., double speed = 4x torque).
Examples: Fans, centrifugal pumps, blowers.
VFD can save energy at lower speeds since less torque is needed.
Constant Horsepower Loads
Torque drops as speed increases (inverse relationship).
Examples: Winders, lathes, grinders.
No energy savings at reduced speeds—power stays constant.
Impact Loads
Sudden, intermittent torque demands (e.g., punch presses).
VFD must handle sharp spikes in current without tripping.
Starting/Breakaway Loads
High initial torque needed to get things moving (e.g., mixers with thick fluids).
VFD should provide 200%+ starting torque briefly.
Real-World Examples
Hoist (Constant Torque): A 1000 kg load needs the same torque whether moving slow or fast. The VFD ensures consistent power.
Fan (Variable Torque): At half speed, torque drops to 25%, saving energy.
Winder (Constant Horsepower): As the drum fills, torque rises, but speed slows to maintain tension.
Picking the Right VFD
KB Electronics offers VFDs tailored to these loads:
KBAC Series: Great for constant/variable torque with a "Power Start" feature for high breakaway loads.
KBDA/KBDF Series: Programmable for flexibility in handling different load types.
Pro Tip:
Check the load’s breakaway torque! If overlooked, the VFD might trip during startup.
Choosing a Variable Frequency Drive isn’t just about horsepower—it’s about matching the drive to your load’s personality. Constant, variable, or impact? There’s a VFD for that.
