The invention relates to an electronically commutated motor in which both the drive current (i2) and the brake current (i2') are monitored. If the drive current is too high, a pulse duty factor is reduced that influences the current in the motor. If the brake current is too high, said pulse duty factor is increased. To this end, an analogous circuit with two current limiting members (131, 161) is provided and a circuit in which these functions are realized by the software of a microcontroller so that the measurement of current is no longer necessary. A combination of the two methods is also possible according to which hardware current limitation and software current limitation interact.

Electronically commutated motor

An energy storage device comprises a flywheel rotor in the form of a spokeless ring of filamentary, composite material rotating around a ring-shaped stator. Along the inner rim of the rotor, there is a layer of magnetically soft iron that forms homopolar, salient pole pairs. An ironless armature winding mounted on the stator extends into an air gap formed between the pole pairs. To bring the rotor up to speed, alternating current is supplied to the armature winding using electronic commutation. The armature current interacts with flux in the air gap to create a force acting to rotate the rotor. During coast down, current may be tapped from the rotor using commutation diodes. The rotor and stator are maintained in axial alignment to each other by magnetic flux produced by a permanent magnet in the stator. An electromagnet incorporated in the stator modulates permanent magnet flux to compensate for any eccentricity between the stator and the rotor that may develop during rotation.

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Energy storage apparatus

A brushless alternator is disclosed having a stationary field coil and core surrounded by a stationary stator coil and core with a cylindrical air gap being defined therebetween A rotor assembly is fixed to a rotatable shaft and has interweaved separate magnetic finger assemblies joined together by a non-magnetic ring wherein these fingers are rotated in the cylindrical gap The stator and field cores are radially disposed with respect to the rotatable shaft The field core axially extends beyond the effective axial length of the field coil and provides at an axial position beyond the effective axial length of the field coil, at least one low reluctance axial flux gap between the field core and the magnetic fingers This flux gap conducts a substantial portion of the flux created by the field coil The field core also serves as a shaft bearing retainer and has a bearing grease reservoir comprising a cylindrical recess adjacent the shaft bearing

Axial air gap brushless alternator

An inertial energy storage device including a synchronous rotary electrical machine for bidirectional conversion between mechanical and electrical energy including: a stator having two axially spaced sets of circumferentially spaced teeth; field excitation means disposed on the stator to provide an axially polarized magnetic field; stator windings including a plurality of coils, each of which surrounds at least one tooth from each set; and a rotor having a plurality of circumferentially spaced teeth facing the stator teeth, and a circumferential flywheel mass radially spaced from its rotational axis; and a motor control circuit including sensor means for sensing the position of the rotor relative to the stator; means, responsive to the sensor means, for generating a waveform for driving the machine when it is operating as a motor; a voltage control circuit for controlling the amplitude of the waveform for driving the machine; and a current control circuit for controlling amplitude of the current provided to the machine.

Inertial energy storage device and synchronous rotary electrical machine for use therein

An electrical stepper motor system is provided in which a microcomputer controlled driver monitors the real time operating parameters of the stepper motor. The driver is controlled by the microcomputer to keep the real time operating parameters of the motor in a range that is governed by limiting parameters. The limiting parameters are determined by the microcomputer on a moment by moment basis in response to changes in certain conditions occurring within the stepper motor, as well as in the outside operating environment. The microcomputer compares the microcomputer determined safe operating parameters with any user stipulated operating parameters, stored in the storage means of the microcomputer, to determine limiting parameters on a moment by moment basis. An encoder senses the position and velocity of the motor and provides appropriate status signals to enable the driver to compensate for position and velocity errors of the stepper motor. An indexer is also provided which provides the driver with pulses that determine the distance, speed and direction of a move. In the illustrative embodiment, the driver, microcomputer, indexer, power supply and encoder circuitry are hybridized on at least one hybrid circuit, each circuit being attached to a heat sinking system, potted in a series of thermally conductive and EMI/RF insulating compounds, and are enclosed in a metallic enclosure that is shielded from outside electrical noise, with the enclosure being directly coupled to the back of the stepper motor to form a compact, unitary device.

Stepper motor system

This disclosure describes a direct current (DC) motor structure having stationary (immovable) field and armature windings A rotor formed of a material having high magnetic permeability and having a plurality of salient poles is rotatably mounted adjacent to the field winding so that the field winding electromagnetically induces magnetic flux in the poles The armature windings are also mounted adjacent to the rotor In operation, the magnetic flux induced in the poles interacts with the current passing through the armature windings The current flow in the armature windings is controlled by a solid-state commutator in a manner normally associated with brushless DC motors By controlling the magnitude of the current supplied to the field windings, the speed of the motor is controlled In addition, the windings can be connected in a series, shunt or compound configuration as desired

Philip A Studer

Papers

Direct current motor with stationary armature and field