Universal DC Motors

Figure 6-5 Brushless DC motor (Cour tesy of Zero Emission Vehicles of Australia and www. electric-cars-are-for-girls.com).

Figure 6-6 DC motor with round stator (Cour tesy of Zero Emission Vehicles of Australia and www.electric-cars-are-for-girls.com).

half the motor), and the distinction between DC motor types blurs. In fact, as seen in Figure 6-5, the brushless motor more closely resembles an AC motor (which you’ll meet in the next section) in construction. Assume that brushless DC motors resemble their permanent magnet DC motor cousins in characteristics—shunt motor plus high starting torque plus linear speed/torque—with the added kicker of even higher efficiency due to no commutator or brushes.

There are other manufacturers of DC motors. They are UQM and AVEOX. For more information, please refer to Chapter 12.

Universal DC Motors

Although any DC motor can be operated on AC, not all DC motor types run as well on AC and some might not start at all (but will run once started). If you want to run a DC motor on AC, you have to design for it. A series DC motor type is usually chosen as the starting point for universal motors that are to be run on either DC or AC. DC motors designed to run on AC typically have improved lamination field and armature cores to minimize hysteresis and current losses (see Figure 6-6). Additional compensating or interpole windings can be added to the armature to further reduce commutation problems by reducing the flux at commutator segment transitions. In general, series DC motors operating on AC perform almost the same (high starting torque, etc.), but are less efficient at any given voltage point.