Brushless DC motor

Fig. 12.11. Brushless DC motors, (a) 6-pole, 3-phase, 18-slot design, (b) Low-intertia disk geometry [43].

Fig. 55. Effect of varying rotor diameter in brushless DC motors based on permanent magnets, (a) Situation for ferrite magnets under various constraints discussed in the main text. The arrow indicates increasing electric loading Q. (b) Envelope of feasible designs (hatched area) based on different permanent magnet materials. The arrows L and BH indicate increasing inductance (L) and increasing (BH)msi%, respectively. (After Howe et al. 1987.)...

Electric fuel pumps Instrumentation gauges Brushless DC motors Actuators Alternators Consumer electronics VCRs and camcorders Cameras... 

Spindle drive Belt drive Direct brushless DC motor... 

Synchronous Motor, Brushless DC-Motors, Synchronous Reluctance, and Permanent Magnet Stepper Motors... 

P. Pillay and R. Krishnan. Application characteristics of pm synchronous and brushless dc motors for servo drives. IEEE Transactions on Industry Applications, 27(5) 986-996, 1991. 

Now suppose the camera is used to visually inspect components as part of a robotic workcell. In this case, the requirements on precision are significantly higher. Consequently, a servo system using a geared DC motor and powered by a PWM voltage amplifier maybe an appropriate choice. If the robotic workcell is used extensively, a more reliable system may be in order. Then a brushless DC motor may be substituted for a higher initial cost. 

The brushless DC motor (BLDC motor) is really an AC motor The current through it alternates, as we shall see. It is called a brushless DC motor because the alternating current must be of variable frequency and so derived from a DC supply and because its speed/torque characteristics are very similar to the ordinary with brushes DC motor. As a result of the brushless DC not being an entirely satisfactory name, it is also, very confusingly, given different names by different manufacturers and users. The most common of these is self-synchronous AC motor , but others include variable frequency synchronous motor , permanent magnet synchronous motor , and electronically commutated motor (ECM). 

Figure 10.22 Diagram showing the basis of operation of the brushless DC motor.

Brushless DC motors can provide extremely accurate and efficient speed control. Digital feedback to the electronics provides the commutation required to set the motor speed. These added benefits come at a higher cost than typical DC or variable frequency AC drives. 

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