BLDC Motors

Overview

                                                                                                                                            

Standard Brushed DC motors have been around for a long time, they are used in many different applications and have proven to be very powerfull and reliable.  Their only downfall has been the brushes, which wear down with time and need to be replaced regularly, and the weight of the rotor which, by design, has many coils whch are sequenced by the commutator, and since only one coil is used at a time this means that at any one time many coils are redundant and adding dead weight.  For motors required to move at constant velocity this could be a benefit, but for quick and accurate stop start applications this is not desireable.
 
BLDC, or Brush-Less DC, motors are DC motors, but they do not have any Brushes, which makes them longer lasting in comparison.  They are constructed in reverse to the normal DC motor, with the magnet on the rotor and the coils, like a 3 phase motor  around the casing, which makes the rotor much lighter, which in turn makes it more agile. And since there are only 3 coils they are more efficient in operation.  In this way BLDC motors can be made much smaller for the same power.  As an example a small BLDC motor the size of a Nema 23 stepper motor will have more than 10 times the torque of the Stepper.
 
However, nothing comes without problems, and the downside to BLDC motors is that they are much more complex to control since commutation must now be done in the drive instead of the motor.  We have worked hard on this over the last 10 years and have now built a range of small to medium size drives that will control them with speed and precision that you will not find with standard DC motors.  All our drives will work with normal brushed DC motors as well, but we do not stock or sell Brushed DC Motors.
 
All the BLDC motors we sell are in the standard Nema frame sizes, to give greater compatability to standards and ease of fitting, however some thought should be given if using them as direct replacements for stepper motors as there are other factors to consider.  Stepper Motors are slow motors, they like to move slowly and are happiest when sitting on 1 fixed position.  Servo motors on the other hand are fast and powerfull and like to move a little quicker.  Most of the motors in our range are 3000rpm to 4000rpm max. speed.  If you were to direct couple a servo to a 5mm pitch screw you would get an operating speed of 4000 * 5, or 20,000mm/min, or 20metres/min max speed!  Servomotors work better through a little gearing, usually a couple of timing pulleys and a belt is enough, to give greater power and resolution while still getting the requitred speed range. 
 
                                                                                             
 
All our motors come fitted with an adjustable incremental encoder with resolutions from 128ppr to 2048ppr.  Our drives use these incrememental encoders in quadrature mode, (recording both high and low transitions on both chanels) which means the resolution is 4 times higher, so with the encoder set to 2048, the motor will actually have 8196 increments per rotation.  At max speed of 4000rpm that relates to 550,000 pulses per second, which is well within the tollerances of our drives.
 
Our standard range of BLDC motors includes:

Watts

Nema

Volts

Shaft Dia.(mm)

Torque (Nm)

Peak Torque (Nm)

Rated RPM

Current (A)

               

50

23

24

6.35

0.22

0.66

4000

2.6

130

23

24

6.35

0.31

0.9

4000

7.3

180

23

24

6.35

0.43

1.2

4000

9.4

220

34

48

9.5

0.7

2.1

3000

6.2

440

34

48

12.7

1.4

4.2

3000

11.9

660

34

80

12.7

2.1

6.3

3000

10

 

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