VARIABLE FREQUENCY DRIVES (VFDs)
Variable Frequency Drives (VFDs) control AC or DC motor speed and torque by varying the frequency and voltage of the motor. These are some of the reasons to consider a VFD or an upgrade to your motor control system:
Controlled Starting Current – An Adjustable Speed AC Drive starts a motor at zero frequency and voltage. As the frequency and voltage “build,” it “magnetizes” the motor windings, which typically takes 50-70% of the motor full-load current. The substantially reduced starting current extends the life of the AC motor. The customer payback is less wear and tear on the motor (motor rewinds), and extended motor life.
Reduced Power Line Disturbances – Using an Adjustable Speed AC Drive eliminates this voltage sag, since the motor is started at zero voltage and ramped up.
Lower Power Demand on Start – If power is proportional to current-times-voltage, then power needed to start an AC motor across the line is significantly higher than with an Adjustable Speed AC Drive.
Controlled Acceleration – An Adjustable Speed AC Drive starts at zero speed and accelerates smoothly on a customer-adjustable ramp.
Adjustable Operating Speed – Use of an Adjustable Speed AC Drive enables optimizing of a process, making changes in a process, allows starting at reduced speed, and allows remote adjustment of speed by programmable controller or process controller.
Adjustable Torque Limit – Use of an Adjustable Speed AC Drive can protect machinery from damage, and protect the process or product (because the amount of torque being applied by the motor to the load can be controlled accurately). An Adjustable Speed AC Drive, on the other hand, can be set to limit the amount of torque so the AC motor never exceeds this limit.
Controlled Stopping – Just as important as controlled acceleration, controlled stopping can be important to reduce mechanical wear and tear — due to shocks to the process or loss of product due to breakage.
Energy Savings – Centrifugal fan and pump loads operated with an Adjustable Speed AC Drive reduces energy consumption.
Reverse Operation – Using an Adjustable Speed AC Drive eliminates the need for a reversing starter, since the output phases to the motor can be electronically changed without any mechanical devices.
Elimination of Mechanical Drive Components – Using an Adjustable Speed AC Drive can eliminate the need for expensive mechanical drive components such as gearboxes. Because the AC Drive can operate with an infinite variable speed, it can deliver the low- or high-speed required by the load, without a speed-increasing or reduction devices between the motor and load. This eliminates maintenance costs, as well as reducing floor-space requirements.