Generator, Inverter, Motor, & Controller Customization

20 hour customization retainer

$1,000

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TorsionTec has patent pending on techniques that allow the construction of efficient high torque generators and motors.  By increasing the number of magnetic poles, the width of the pole is decreased and the amount of "back-iron" required to conduct the magnetism is also decreased.  The rotor is hollow, dramatically decreasing the weight.  Proprietary geometric relationships in the rotor and stator concentrate the magnetism and maximize electrical and magnetic conduction through the stator windings improving power density up to ten times (10X or 1,000%) vs conventional induction motors/generators.  This geometry also creates a smooth 3-phase sine wave in the stator windings that reduces losses and cogging.
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Comparison to automotive alternators and 3-phase induction motors

An alternator typically contains 2 claws that limit the axial length of the magnetic conduction path (both rotor & stator).  Increasing the length  (L) increases the torque linearly and increasing the rotor diameter (D) increases the torque (T) by the square (D²).  We have derived the formula T=D²L by measurement of prototype parameters and mathematical analysis.  A 3-phase induction motor creates a 3-phase sine wave by using lap winding techniques and skewing the rotor.  The ability to efficiently increase the number of poles and thereby achieve the hollow ring-like structure is severely compromised.  Additionally, electrical and magnetic conduction through the stator windings is limited due the requirement of inducing a (slipping) magnetic field into the rotor from the stator.

Motor Controllers and Inverters

Alternators use 6 (3-phase bridge) diodes to rectify the 3-phase sine wave generated in the stator windings.  The diodes automatically conduct at the appropriate time so commutation circuitry is not necessary.  This works fine when used as a generator, but to make the device work as a motor requires conduction control in the 3-phase bridge.  This is achieved by replacing the diodes with power transistors (MOSFETs or IGBTs) and controlling their conduction with rotor position sensing (Hall Effect / Optical / Back-EMF) and the appropriate logic circuits that turn on the transistors at the appropriate time to provide commutation.  PWM (Pulse Width Modulation) circuitry provides control of the current and voltage applied to the windings which controls the torque and speed of the motor.  Similar techniques can be applied to the power transistors to perform grid-tie or stand alone inverter functionality.

Wound Rotors - Slip Ring / Commutator Elimination

Early alternators used brushes and metal slip rings to conduct electrical current into the rotor.  Even today most high power DC traction motors and generators use brushes and metal bars to conduct current to the rotor and also provide commutation.  Some alternators and generators use inductive coupling techniques to eliminate the brushes altogether.  These alternators still use a central electromagnet but it is stationary and the magnetism is coupled by proximity to the rotor (axial length limitation).  The generators use a small secondary rotor mounted on the same shaft that provides excitation of the main rotor windings (speed dependent).  We have found a different technique that has no axial length limitation but still provides speed independent inductive coupling.