Electricity: motive power systems – Synchronous motor systems – Hysteresis or reluctance motor systems
Patent
1991-02-11
1992-03-17
Smith, Jr., David
Electricity: motive power systems
Synchronous motor systems
Hysteresis or reluctance motor systems
H02P 540
Patent
active
050971913
DESCRIPTION:
BRIEF SUMMARY
INDUSTRIAL FIELD OF THE INVENTION
The present invention relates to a reluctance type electric motor which can be driven at low voltage.
BACKGROUND OF THE INVENTION
Traditionally, the reluctance type electric motor has been capable of providing large output torque but involved increased applied voltage. For example, even the applied voltage of a reluctance type electric motor of 100 watt output was 100 volts or over.
In an example of such traditional reluctance type electric motor of above, if the applied voltage is low of about 20 volts for example, the speed of rotation was reduced and the utility was lost.
Further, the speed was lowered, and if the speed was increased, then the efficiency was considerably deteriorated.
In other words, the magnetic path of the excitation coil of the reluctance type electric motor is closed by the magnetic pole and the salient pole, so that the inductance of the excitation coil of the reluctance type electric motor is considerably larger than that of the armature coil of well-known magnet armature.
Therefore, the output torque increases. However, because it takes time to accumulate and to discharge the magnetic energy that is accumulated in the excitation coil, the reduced torque and the counter torque result because the width between the leading edge and the falling portion of the excitation current increases.
Therefore, the speed of rotation of the motor is reduced extremely. There is no means but to increase the applied voltage in order to obtain high efficiency at high motor speed rotation. An object of the present invention is therefore to provide a highly efficient reluctance type electric motor which turns at high speed on the low applied voltage.
DISCLOSURE OF THE INVENTION
In accordance with the present invention, the circuit thereof comprises a first means which converts the accumulated magnetic energy into the magnetic energy of a second exitation coil to be energized next when the current supplied to a first excitation coil is shut off, thereby to quickly discharge the magnetic energy of the first excitation coil and to accumulate the magnetic energy of the second excitation coil.
Therefore, a reverse current prevention diode is provided to prevent the flow back of the foregoing discharged electric power to the DC power source.
Then, when the electric current supply to the first excitation coil and the second excitation coil is changed instantaneously without a time delay, the first means stated above will do. However, when a certain time delay is involved and if the magnetic energy of the first excitation coil is charged into a small capacity capacitor to obtain high voltage for accumulating the magnetic energy of the second excitation coil, the discharging and accumulation of the magnetic energy become quick and the occurrence of the reduced torque and counter torque is prevented.
For this reason, a reverse current prevention diode and a capacitor of small capacity are provided as a means to prevent the foregoing conditions.
Further, when the magnetic energy accumulated in the first excitation coil is discharged, it results in a loss of Joule heat due to the resistance of the excitation coil, that is, the loss of copper and the loss of iron.
Therefore, because the discharged magnetic energy is reduced by a fixed amount, the start-up of the excitation current may not be sufficient. It stands to reason that the copper loss and iron loss of the second excitation coil will have similar influence on the start-up of the excitation current.
In order to remove such inconvenience, a means is provided which increases the current value of the final period by a fixed value than the current value of the initial period (the current value when the start-up is completed) respectively of the excitation current of the excitation coil.
Because the current value of the final period of the excitation current of the first excitation coil is increased by a fixed value, the accumulated magnetic energy is also increased accordingly.
This magnetic energy is converted into the m
REFERENCES:
patent: 4868478 (1989-09-01), Hedlund et al.
patent: 4933621 (1990-06-01), MacMinn et al.
patent: 5043643 (1991-08-01), Hedlund et al.
Kabushikigaisha Sekogiken
Smith Jr. David
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