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Why Use an Inverter or VSD?

People often ask what the benefits are of using an Inverter (Variable Frequency Drive)?

Read on to find out…

Energy Savings with VSDs (Variable Speed Drives)

If you have an AC motor driven process that does not need to be run at full speed all of the time, then you can vastly reduce your energy costs by controlling the motor with a Variable Speed Drive (VSD). Variable Speed Drives (also referred to as Variable Frequency Drives) allow you to match the speed of the motor-driven equipment to the actual requirement.

Speed can be varied either locally using the keypad attached to the drive or with any of our remote operator pendants.

Remote Inverter Pendant
Remote Operating Pendants
Energy Consumption

Variable Speed Drives (VSDs) allow you to consume less energy than other speed control techniques when load requirements are less than full speed, as is usually the case in HVAC applications. We have designed a useful Infographic to highlight some of these benefits:

ic: Inverter Energy Savings
Why Variable Torque Loads Offer Great Energy Savings

In variable torque applications, the torque required roughly follows the square of the speed, and the horsepower required varies approximately with the cube of the speed. This results in a large reduction of horsepower for even a small reduction in speed. A motor used in a variable torque application will consume only 25% as much energy at 50% speed as it will at 100% speed. This is referred to as ‘Affinity Laws’, which define the relationships between speed, flow, torque, and horsepower.

Variable Torque Versus Constant Torque

Variable Speed Drives, and the loads they are applied to, can generally be divided into two groups: constant torque and variable torque. The energy savings potential of variable torque applications is much greater than that of constant torque applications. Variable torque loads include centrifugal pumps and fans, which make up the majority of HVAC applications. Constant torque loads include vibrating conveyors, punch presses, rock crushers, machine tools, and other applications where the drive follows a constant V/Hz ratio.

Extended Equipment Life and Reduced Maintenance

Single-speed starting methods start motors very abruptly, subjecting the motor to a high starting torque and to current surges that are up to 10 times the full-load current. Variable speed drives, on the other hand, gradually ramp the motor up to operating speed to lessen mechanical and electrical stress, reducing maintenance and repair costs and extending the life of the motor and the driven equipment.

Soft starts, or reduced-voltage soft starters, are also able to step a motor up gradually, but drives can be programmed to ramp up the motor much more gradually and smoothly and can operate the motor at less than full speed to decrease wear and tear. Variable speed drives can also run a motor in specialized patterns to further minimize mechanical and electrical stress. For example, an S-curve pattern can be applied to a conveyor application for smoother decel/accel control, which reduces the backlash that can occur when a conveyor is accelerating or decelerating.

If you would like any more information about energy savings with AC Inverters, please contact us:

Our engineers can attend your site and offer recommendations where possible savings can be made.