Motion Control Resources
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Brushless DC – A Practical Guide to Implementation
by Mark Lewis, VP - Marketing & Sales - Dart Controls, Inc.
Dart Controls, Inc. Posted 01/28/2015
Brushless DC (BLDC) motors have the performance advantages of DC permanent magnet motors without the need for motor brush maintenance. BLDC motors have the additional advantages of very high base speed (20,000
Drive & Motor Connection - The market for BLDC drives and motors is fragmented – evidenced by the number of companies who list themselves as Motor Manufacturers (133) and Brushless DC Drive Manufacturers (50)1. There is little standardization in terms of motor wire color coding, terminology or orientation – with 8 or more wires to connect from the motor it is very easy to misconnect to the drive causing erratic performance or damage. It is not unusual that the drive and motor will come from separate suppliers to meet the users’ requirements.The recommendation when sampling a BLDC system is to request the motor, motor timing diagram and performance curve data all be sent to the drive manufacturer (or drive to the motor manufacturer). This will allow the suppliers involved to establish the correct connection and send the tested motor and drive to the user ready for evaluation.
Drive & Motor Voltage - There are defacto standard BLDC motor armature voltages on the market, with the most common being 24V. Experience finds the designer/user has already selected the motor prior to investigating drive options. When selecting a drive, there seems to be an expectation to apply (example) 120VAC source power and get 0-24
Drive & Motor Speed Regulation – The majority of BLDC drives are sensored (closed-loop) design. This means the drive is expecting some sort of feedback from the motor to verify its speed / rotor to phase position relationship to maintain electrical commutation by the drive. This feedback is accomplished using (typically) hall-effect transistors in the motor; or an encoder. Some drives and motors are being designed as ‘sensor-less’. The key here is a sensored drive is designed for use with a sensored motor. There are applications for both sensored and sensor-less designs. The recommendation to equipment designers / industrial users who wish to regulate the speed of their motors under varying conditions use a sensored design.
BLDC technology is gaining momentum as equipment designers and users consider size, weight, performance and long-term maintenance in their selection process for motor / drive packages. In the 1/2HP and below market, BLDC is a viable alternative to brushed DC and AC motor / drive packages in terms of overall cost. Some applications (pumps and fans) see distinct advantages in BLDC through the unique ability to run at higher speeds to produce equal throughput, at a smaller size / weight / cost.
1Source - ThomasNet®
Mark Lewis is Vice President – Marketing and Sales for Dart Controls, Inc. Dart designs and produces