Electricity: motive power systems – Limitation of motor load – current – torque or force
Reexamination Certificate
2001-07-13
2003-10-07
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Limitation of motor load, current, torque or force
C318S254100
Reexamination Certificate
active
06630806
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to motors which are used for generating a torque and generators which are used for generating electricity.
BACKGROUND OF THE INVENTION
A typical electric motor consists of a stator and rotor.
The operation of an electric motor is based on the principal that an electric current through a conductor produces a magnetic field, the direction of current in an electro-magnetic such as a coil of wire determines the location of the magnets poles and like magnetic poles repel and opposite poles attract.
The stator which is typically called the field structure establishes a constant magnetic field in the motor.
Typically the magnetic field is established by permanent magnets which are called field magnets and located at equally spaced intervals around the rotor.
The rotor or armature typically consists of a series of equally spaced coils which are able to be energised to produce a magnetic field and thus north or south poles.
By keeping the coils energised the interacting magnetic fields of the rotor and the stator produce rotation of the rotor.
To ensure that rotation occurs in a single direction a commutator is typically connected to the windings of the coils of the rotor so as to change the direction of the current applied to the coils.
If the direction of the current was not reversed the rotor would rotate in one direction and then reverse its direction before a full cycle of rotation could be completed.
The above description typifies a DC motor. AC motors do not have commutators because alternating current reverses its direction independently.
For a typical AC motor such as an induction motor the rotor has no direct connection to the external source of electricity. Alternating current flows around field coils in the stator and produces a rotating magnetic field. This rotating magnetic field induces an electric current in the rotor resulting in another magnetic field.
This induced magnetic field from the rotor interacts with the magnetic field from the stator causing the rotor to turn.
An electric generator is effectively the reverse of an electric motor. Instead of supplying electricity to coils of either the stator or rotor, the rotor or armature is rotated by physical forces produced by a prime mover.
In effect a generator changes mechanical energy into electrical energy.
SUMMARY OF THE INVENTION
The present invention is aimed at providing an improved rotary device which operates with improved efficiency compared to conventional rotary devices.
The present invention is also concerned with providing a system for controlling a rotary device which is able to generate electrical and/or mechanical energy.
According to the present invention there is provided a system for controlling a rotary device, the system comprising a controller and a rotary device, which has a stator and rotor, wherein the controller is connected to the rotary device to control rotation of the rotary device, and wherein the controller is adapted to periodically energise at least one energising coil of the device to create a magnetic field of a polarity which induces the rotor to rotate in a single direction and wherein the controller is switched off so as to de-energise the energising coil when other forces, being forces other than those resulting from the energised energising coil produce a resultant force which induces rotation of the rotor in the single direction.
Preferably the controller is adapted to energise the energising coil for a period during which the resultant force from the other forces acts to rotate the rotor in the opposite direction, whereby the force applied by the energising coil overcomes (is greater than) the resultant force.
The controller is preferably adapted to switch off to de-energise the energising coil before the resultant force is zero.
The controller preferably is adapted to switch off to de-energise the energising coil for a period before the resultant force is zero, and to allow back EMF induced by other forces to urge the rotor to rotate in the single direction before the resultant force is zero.
Preferably the resultant force excludes forces arising from back EMF.
The energising coil may be adapted to be energised by the controller through a predetermined angle of a complete revolution of the rotor.
Alternatively the energising coil is adapted to be energised by the controller for a predetermined period of time for each revolution of the motor.
Preferably the/each energising coil is energised more than once during a single revolution (cycle) of the rotor.
The/each or at least one energising coil may be energised each time the resultant force applies a force to the rotor in the opposite direction.
The/each or at least one energising coil may be energised by a periodic pulse applied by the controller.
The periodic pulses are preferably all of the same sign.
The/each or selected ones of the energising coils are energised whenever the resultant force is in the opposite direction and then for a period less than the period during which the resultant force changes from zero to a maximum and back to zero.
According to one embodiment the stator has the at least one energising coil.
The rotor may have at least one magnetic field generating means which is able to generate a magnetic field which interacts with the magnetic field generated by the/each energising coil when energised, to apply a force to rotate the rotor in one direction.
The/each energising coil preferably includes a magnetic interaction means which is adapted to either repel or attract the magnetic field generating means.
According to another embodiment the magnetic interaction means is adapted to attract the magnetic field generating means.
The magnetic interaction means may comprise a ferrous body or body of another substance which is attractable to a magnetised body.
The magnetic field generating means may be a permanent magnet.
The magnetic interaction means may be an iron core or a permanent magnet.
Preferably the magnetic field generating means comprises a permanent magnet, or member attractable to a magnetised body.
The stator preferably comprises a plurality of energising coils evenly spaced around the rotor.
Each energising coil is preferably an electromagnet.
Preferably the or each energising coil includes the magnetic interaction means through its coil.
Preferably the rotor comprises a plurality of evenly spaced magnetic field generating means.
According to one embodiment the rotor comprises a plurality of evenly spaced permanent magnets.
The evenly spaced permanent magnets may all be of the same polarity.
The evenly spaced magnetic field generating means may be energisable coils simulating magnets.
Preferably the poles of the magnetic field generating means are all the same.
The magnetic poles produced by energised energising coils may be the same as that for the magnetic field generating means.
According to an alternative embodiment an alternating pattern of poles for the energising coils is provided.
According to another embodiment an alternating pattern of permanent magnets is provided for the rotor.
According to a further embodiment of the present invention the stator has a plurality of magnetic flux generating means.
The magnetic field generating means for the stator may be permanent magnets.
Preferably the rotor comprises a plurality of energising coils and a commutator.
The rotor may be an armature and the stator may be a field winding.
Preferably the rotor magnetic field generating means is energised by an external power supply being DC or AC current.
The stator magnetic interaction means may be energised by coils operating on AC or DC current.
According to one embodiment the stator includes at least one induction coil which is adapted to have a current induced therein by the magnetic field generating means of the rotor.
The/each induction coil may be separate from the/each energising coil.
The/each induction coil may also be the energising coil.
The/each energising coil may be adapted to be connected to an output circuit whereby current induced in th
Brits Ludwig Emma
Christie Victor John
James Ray and Associates
Ro Bentsu
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