Variable Frequency Drive Basic Theory & Power Flow Explained
An introduction to variable frequency drive motor control technology and VFD power flow theory explained.
Description
This short course is designed to help an electrical technologist, technician, student, or experienced tradesperson to quickly get up to speed when learning about variable frequency drives (VFDs). The course is also useful for engineering students when understanding important VFD power and control concepts.
A theoretical understanding of power flow and components is crucial when installing, commissioning, and troubleshooting variable frequency drive motor control systems.
Part One
The first portion of the course uses simple graphics to explain the functionality of the power and control sections of a VFD. Important drive power sections are discussed such as the converter, dc bus or link and the inverter section. The VFD control section is broken down into subsections with each part being explained.
Part Two
The second part of the course uses a VFD power schematic diagram to explain the power flow through each electronic power component in the drive. This video lesson describes the power flow through all sections of the VFD. The PWM inverter output waveform is shown and changing the carrier, or switching frequency is explained and demonstrated. The PWM waveform is shown at different carrier frequencies and output frequencies. The lesson also focuses on the DC link or "bus" and how energy is returned from the motor and is sent to a braking resistor. The front-end active drive is shown and briefly discussed.
An assignment is attached to each video lesson along with an answer key. Also, to review information covered, there is a quiz at the end of each section.
What You Will Learn!
- The purpose of variable frequency drive (VFD) motor control.
- List the two main sections of a VFD and list the subsections within these sections.
- Describe the various control functions of a modern VFD.
- List VFD input and output (I/O) signal types, analog and digital.
- Describe how a VFD multifunction input and output works and how these functions are assigned.
- Describe the power flow from the AC line supply to the motor in a modern VFD.
- Name each electronic power component in a modern VFD.
- Explain how energy is returned from the motor and how the DC link section or bus deals with this energy.
- Understand important terms such as carrier frequency, switching frequency, pulse width modulation (PWM), volts per hertz or scalar control and dc injection.
Who Should Attend!
- This short course is designed to help an electrical technologist, technician, student, or experienced tradesperson to quickly get up to speed when learning about variable frequency drives (VFDs). The course is also useful for engineering students when understanding important VFD power and control concepts. A theoretical understanding of power flow and components is crucial when installing, commissioning, and troubleshooting variable frequency drive motor control systems.