eDrive - Summer 2015 - (Page 12)

Feature Article A High Efficiency, Low EMI, Low Cost Universal Motor Gary Box Digital Power Engineering Imagine a simpler and lower cost alternative to high efficiency AC induction motors, brushless permanent magnet motors and expensive drives. For applications less than 10 HP, a Brushless Universal motor, can deliver super-premium IE4 efficiency without permanent magnets (PM), expensive drives or the typical power quality problems inherent in AC or PM motor/ drive systems at a projected system price up to 50 percent less than current solutions. This motor and drive builds on the elemental sinusoidal creation of motion technology developed by Nicola Tesla and uses cutting edge technology to create high efficiency, environmental compatibility and controllability in a single, drop-in package. The Back Story The electronically controlled motor (ECM) has a curious pedigree. Before the dawn of semiconductors, precise electric motion was the largely the province of DC brush motors, constant speed power was the province of AC induction motors and both were completely electromechanical. DC Permanent magnet brush and brushless motors were developed in the 1970s, coincidently with early electronic controls. Electronic drive technology continued to develop as a branch of the much larger switching power supply market, sharing many circuits and components with its larger relative. In the mid 1980s high margin industrial automation dominated the ECM scene, neodymium magnets were developed, and electronic control techniques appeared, such as field oriented control for induction motors, compatible with the electronic hardware of the day. Beyond Figure 1. servos, the ECM market was now dominated by industrial automation applications and variable frequency drives feeding induction motors or inverter drives feeding PM motors running on three phase power. By the late 1980s all such drives exhibited the basic form they have today, as seen in Figure 1. The problem with this scheme is that it takes the perfectly good AC sine wave from the power grid, rectifies and filters it to DC, chops it at 20 KHz or so, modulates it with pulse width modulation (PWM) to derive another perfectly good sine wave, and puts it into the motor. All of the power into the motor gets chopped. There are three unintended consequences of this approach that are becoming problematic as ECMs migrate from industrial level factory automation systems to replacing single phase AC induction motors in HVAC, pump and compressor applications as a result of energy efficiency legislation. First, on single phase AC, the AC-DC rectifier of the ECM draws a highly distorted current waveform from the power grid, leading to power quality problems such as nuisance circuit breaker tripping and possible fire hazards on building ground wires, particularly when the motor draw is the near the capacity of the branch circuit. Second, the technique of chopping all of the power going into the motor at 20 KHz produces a large electromagnetic interference (EMI) footprint, a very real operational hazard as the Internet of Things (IoT) proliferates with sensitive sensors and networks, some operating in proximity to the motors and many operating or communicating on the very frequencies being spuriously created by the drive. 12 Summer 2015 www.e-DriveOnline.com http://www.e-DriveOnline.com

Table of Contents for the Digital Edition of eDrive - Summer 2015

Comparing Efficiency and Capabilities of Hybrid Stepper Motor Actuators to Can Stack Stepper Motor Actuators
Motion Control in Packaging: 10 Tips for Improvement...Plus One for Good Measure
A High Efficiency, Low EMI, Low Cost Universal Motor
Simplifying the Machine Engineering Design Process Through Improved Energy Efficiency of Electric Drives
Motors & Drives
ICs & Semiconductors
Components
Conference Preview: Motor & Drive Systems
Industry News
Calendar of Events

eDrive - Summer 2015