Electricity: motive power systems – Battery-fed motor systems
Patent
1979-12-13
1982-09-07
Truhe, J. V.
Electricity: motive power systems
Battery-fed motor systems
318254, 320 2, 307149, H02P 500
Patent
active
043486193
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to variable reluctance electric motor systems in which the power for driving the motor is taken from a rechargeable battery. The invention is concerned with the charging of the battery from a main supply.
SUMMARY OF THE INVENTION
According to the present invention a variable reluctance electric motor system includes a variable reluctance motor having main windings and auxiliary windings closely coupled to the main windings, a main storage battery for driving the motor, D.C. supply terminals and a power converter circuit for charging the battery from the D.C. supply, in which the motor is included in the power converter circuit to function as an isolating transformer to isolate the battery from the supply when on charge.
The power converter circuit may include solid state switching devices supplying unidirectional pulses of current to a winding of each of one or more phases such pulses being synchronized with the rotation of the motor when driving the motor but free-running when charging the battery.
The invention is primarily, though not exclusively applicable to variable reluctance motor systems incorporated in battery propelled vehicles. In the usual form of charger if a step down or step up of voltage is required a transformer is necessary and even where there is no change of voltage a transformer will generally be required to ensure isolation of the battery from direct connection to the main supply. In the case of a highpower charger the weight and bulk of a transformer for mains frequency will be very substantial, and the elimination of such a transformer may make it practical to carry the charger on the vehicle.
In a variable reluctance motor pulses of current are delivered from a D.C. supply to the phase windings of the motor, and transfer energy from the supply to a winding as the current rises, after which it is desirable to recover energy from the winding. This is commonly done by providing each phase of the motor with an auxiliary winding closely coupled to the main winding.
In accordance with the present invention these closely coupled main and auxiliary windings are used as a transformer when charging the battery from a main supply to isolate the battery from direct connection with the supply, and if necessary provide a change of voltage, thus eliminating the expense, space requirement and weight of a separate transformer.
Moreover, in such a variable reluctance motor system, each auxiliary winding is generally connected in series with a diode across the battery so that this portion of the circuit need not be disturbed when using the windings for charging.
Thus in one form of the invention each phase of the motor has a main winding connected in series with a main thyristor between the D.C. supply terminals, and an auxiliary winding closely coupled with the main winding and connected in series with a diode across the battery terminals, means being provided for firing and commutating the main thyristors, and means for connecting the D.C. supply terminals to a rectified A.C. main supply for charging the battery, and means for for connecting the D.C. supply terminals to the battery terminals for driving the motor.
The system may include a current transducer arranged to control the commutation of the switching devices to take place when the current reaches a predetermined value, when charging the battery. Alternatively or in addition it may include timing means arranged to introduce a predetermined time interval between pulses, when charging the battery. For example each pulse may be initiated under the control of a timer and commutated under the control of a current transducer when the current reaches a predetermined value.
For driving at low speed it will in any case generally be necessary for the variable reluctance motor to operate in a chopping mode, that is to say one in which the switching device of each phase is commutated when the current rises above a predetermined value and fired and commutated again, severa
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Davis Rex M.
Ray William F.
Chloride Group Limited
Moose Richard M.
Truhe J. V.
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