Small Electric Motors, Permanent Magnet DC Motors

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Wondering which type of miniature motor would work best? Learn more about the characteristics and advantages of the different motor technologies.

Brushless DC Motors

Brushless DC
Details	Characteristics	Advantages
Permanent Magnet DC Design	Essentially linear torque/speed curve, with torque proportional to current and speed proportional to voltage	Ease of speed and position control
Brushless Design	Life is not limited by brush wear but only by wear in ball bearings	Very long life, high reliability, insensitive to environment. No arcing, dust free. Reduced audible and electrical noise
Static winding attached to motor housing	Improved heat dissipation	Overload capability
Slotless Configuration	No detent torque	Excellent velocity smoothness
Versions without hall sensor	Typically used in spindle applications	Cost effective. Less sensitive to environment. Only three connecting wires.
Versions with hall sensors	Typically used in applications where speed or load variation are needed	Very simple commutation circuitry
Versions with encoder or resolver	Typically used in incremental motion	Very precise speed and position control

Brush DC Motors

Brush DC
Details	Characteristics	Advantages
Ironless Rotor	Low moment of inertia	High acceleration. Ideal for incremental motion; Linear speed-torque function. Insensitive to shocks
	No hysteresis and eddy current losses	High efficiency, low losses from friction only. Ideal for battery operation
	No magnetic saturation	High peak torques without the risk of demagnetization
Central Stator Magnet	High power per size and per weight	Ideal for portable or small equipment or requiring small dimensions
Small Sized Bearings	Low viscous damping	High peak speeds, very low speed dependent losses, low starting voltage
Precious Metal Commutation System	Low friction, little electrical noise	Low losses and wear, low electromagnetic interference
Copper-graphic commutation	High current densities may be commutated	High continuous and peak torques without the risk of demagnetizing to motor. Very long life. Ideal for chopper drivers
	Rated rotor temperature up to 155 degrees Celsius.	Continuous torque is exceptionally high for the motor size, reducing the weight, dimensions and the cooling system
	Very compact commutation system	Excellence resistance to shocks and vibration
	High torque to inertia ratio	High acceleration, short mechanical time constant

Stepper Disc Magnet Motors

Stepper Disc Magnet
Details	Characteristics	Advantages
Thin mulitpolar rare earth disc magnet	Very low rotor inertia	Very high acceleration
Short iron circuit made of SiFe laminations; Coils placed near to the air gap	Low iron losses	High start/stop frequencies
	More torque at high step rates	High speeds
Independent magnetic circuit	No coupling between phases	High power/volume ratio
Simple magnetic circuit	Sinusoidal torque function, low detent torque	Superior angular resolution in microstep mode
Optimally designed magnetic circuit	Torque constant is linear up to 2 to 3 times nominal current	High peak torques
High energy magnet	High power to weight ratio	For motors in mobile applications

Stepper Can Stack Motors

Stepper Can Stack
Details	Characteristics	Advantages
Radially magnetized permanent magnet rotor	High torque to size ratio	Machine size reduction
Bobbin wound coil design	Uniolar/Bipolar windings can be designed for optimum performance	Tailoring to exact needs of application
Sintered bronze bearing design – Ball bearings option	Long life lubrication	Increased warranty on machine
Step angle variation – 3.6 degree to 20 degree	Design capability for finer mechanical resolution	Finger resolution required
Simple motor construction	Simple mechanical construction with proven design characteristics	Customization to meet application demands

Stepper Hybrid Motors

Stepper Hybrid
Details	Characteristics	Advantages
Aluminum housing design	Superior heat dissipation	Increased duty cycle improves torque
Multi-toothed rotor and stator – step angles down to 0.9 degree	Fine mechanical resolution	Higher precision in application
Captured bearings	Prevents bearing spinout	Noise reduced during operation
Captured bearings	Linear actuator axial play reduced to zero	Linear axis eliminates slippage during operation
Stator enhanced magnets	nUp to 40% more torque in same package	Reduced size on each axis
Precision radial ball bearing design	Mechanical and electrical modifications available	Customization to meet application needs

Digital Linear Actuators

Digital Linear Actuators
Details	Characteristics	Advantages
Can Stack design with threaded rotor and bobbin wound coil	Windings can be designed for optimum performance	Optimized per application requirements
Stub acme thread design	Various linear step resolutions - .0005 to .0040 inch	Fast, powerful and precise positioning
Simple motor construction	Simple mechanical construction with provden design characteristics	Customization to meet application demands; External components reduced in application
Captive and non-captive designs	nOptions to conform to space requirements	Machine size reduction
Precision radial ball bearing design	High force to size ratio	Customization to meet application demands

Gearheads

Gearhead
Details	Characteristics	Advantages
Spur gear concept: Only 1 transmission point per train	Low friction per train. Arrangement of several trains as intended by the designer. Input and output shaft not necessarily in line. Two output shafts possible.	Good efficiency, about 0.9 per train. Long gearbox of smaller diameter or short gearbox of large diameter. Free choice for placing the motor relative to the output shaft. Mounting of a sensor, a potentiometer etc.
Input wheel made of special grade plastics	Reaction of mechanical noise generated at high motor speeds	Silent functioning
Planetary concept: 3 or 4 transmission points per train	Reduction ratio per train is higher but so is friction. Can transmit higher torques. Input and output of a train have the same direction of rotation. Less backlash.	Less trains for a given reduction ratio efficiency about 0.85 per train. Very compact gearbox for its performance. For any number of trains, the load always rotates in the same direction as the motor. Smaller shock in case of a rapid reversal of motor rotation.

Encoders

Encoder
Details	Characteristics	Advantages
DC tachometer: V (velocity sensor), ironless rotor, commutation system made of precious metals	Delivers a continuous signal, adds neglectable inertia, constant signal quality	Easy control even at very low speeds, little additional load for the motor, Low sensitivity to hostile environements
Magnetic encoder: P (position sensor), encoder integrated in the motor, position monitored by hall sensors	Simple construction, compact design, two output channels	Insensitive to hostile environments, negligible increase in length of the unit, very low current consumption, high reliability and long life
Optical encoder: P+V	High resolution, two channels, plus home position, signal level very stable, cuts LED supply at stall, no thermal drift	Very precise positioning, facilitates counting the number of revolutions, no phenomenon of aging, lower consumption and lower temperature rise, insensitive to temperatures, small dimensions