AC and DC in Motor Control — Lesson 9

This lesson covers the fundamental concepts of Alternating Current (AC) and Direct Current (DC) in the context of motor control. It explains how a controller maintains DC entities, the advantages of VD and VQ, and the necessity of switching between AC and DC. The lesson also delves into the characteristics of sinusoidal waveforms, the concept of Root Mean Square (RMS), and the conversion of DC into AC using Pulse Width Modulation. The lesson further discusses the creation of three-phase AC from DC using a hex bridge and the concept of rotating vectors. For instance, it explains how a motor powered by a 48-volt battery can achieve different phase and line voltages.

Video Highlights

00:17 - Introduction to the controller
01:35 - AC alternating currents and their characteristics
03:25 - Discussion on three-phase circuit and star connected motors
10:25 - Conversion of DC into AC using pulse width modulation
19:43 - How to get three-phase AC from DC using a hex bridge
25:33 - Home assignment

Key Takeaways

- A controller's job is to maintain DC entities, VD and VQ, which are advantageous due to their constant nature.
- Motor control involves constant switching between AC and DC as the motor runs on AC while control is executed in DC.
- Sinusoidal waveforms, characterized by amplitude, frequency, and phase, are integral to AC.
- The Root Mean Square (RMS) is a measure of the magnitude of a sinusoidal waveform.
- Pulse Width Modulation allows the conversion of DC into AC by varying the on-off time of a switch.
- A hex bridge, consisting of six switches, can convert DC into three-phase AC.
- The sum of three-phase AC results in a rotating vector, which is 1.5 times bigger than the individual phases.