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January Meeting: Variable Frequency Drives

Wednesday, January 15, 2020

Eventbrite - ISA January: Variable Frequency Drives

Member: $20
Non-Member: $25
Student Member: $15

Skylar Dhaese will be presenting on variable frequency drives.


What is a VFD? To answer this, let’s first take a step back and look at motors. For most industrial process applications, there are two types of motor; DC and AC. In both, amperage is proportional to torque. By limiting the amperage allowed to a motor, it’s possible to also limit the torque. Controlling speed is more difficult. For a DC motor, changing the voltage input to the motor will change the speed. This could be as simple as changing the resistance in the circuit with a potentiometer. In contrast, because AC motor speed is determined by electrical frequency, changing the speed of an AC motor requires running AC power through a rectifier, a choke, a DC bus, and a series of insulated-gate bipolar transistors with integrated logic.

This process is a lot more complicated than adding a resistor to a DC circuit, so why then do AC motors have such prevalence in industrial applications? While AC motors may be electrically complex, they are mechanically simple. Compared to DC motors, AC motors have fewer moving parts, require less maintenance, and survive longer in the field. On top of this, AC motors cost less than similarly sized DC motors. Price wins. Not every application runs at 60 Hz, so this brings us back to the original question – what is a VFD? A VFD, or variable frequency drive, is an electrical device that combines the complicated circuit for changing electrical frequency into a single box for controlling the speed of an AC motor. AC power enters the VFD at 60 Hz and leaves at the exact frequency necessary for the application, whether it’s 3 Hz or 300 Hz.

VFDs have been widely adopted in the industrial space, and their use continues to grow. Not only do they provide accurate speed control (without feedback in some cases), they are also capable of reducing energy costs and optimizing processes. From small conveyors to 1000 Hp compressors, VFDs are used across industry. In this presentation, I plan to discuss how VFDs work, where they are used, and best practices for implementation. We’ll dive deep into the complicated circuitry at work for frequency modulation and cover ways to protect your local power grid and your motor while using VFDs.

Presenter Bio:

Skylar graduated from the University of Wisconsin with a B.S. in Engineering Mechanics and Astronautics in 2016. After quickly realizing he didn’t want to be stuck behind a desk designing ailerons, he moved to Colorado and joined with AAP Automation as a sales engineer. Skylar’s focus is low-voltage controls, including VFDs. In his four years with AAP, Skylar has developed proficiency in control system design and programming. Skylar’s main focus is spreading the good word about VFDs around all of front-range Colorado.

6:00 – 6:30 Arrival and Registrations
6:30 – 7:00 Food and Socializing
7:00 – 8:00 Presentation

Past Events

October 2019 Meeting: Hydrogen Energy Readiness

September 2019 Meeting: Unser Racing Social Event

May 2019 Meeting: Building a Calibration Plan

April 2019 Meeting: Rescheduled for May

March 2019 Meeting: Guided Wave Radar – Theory of Operation and Best Installation Practices

February 2019 Meeting: Emerson Micro Motion Tour

January 2019 Meeting: NREL Tour

October 2018 Meeting: 2018-2019 Social Kickoff (Axe Throwing!)