Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
1999-06-10
2001-07-24
Brown, Glenn W. (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S545000, C324S546000, C318S490000, C318S648000, C702S057000, C702S058000
Reexamination Certificate
active
06265891
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention is directed to an apparatus for detecting a short-circuit in a coil of an electric motor such as a switched reluctance motor.
Japanese Patent Laid-open Print No. Hei. 10-42586, which was published on Feb. 13, 1998 without examination, discloses a driving circuit for a brush-less motor. In this driving circuit, upon detection of a continuous excess current flow through a coil for a determined time duration, such a continuation of the excess current flowing is regarded as an abnormal condition which makes the driving circuit stop the motor. Thus, in the event of a short circuit in a coil which causes an excess current flowing through a coil which is similar to the above, the motor is made to stop.
However, the foregoing concept cannot be applied to another type electric motor such as a switched reluctance motor. In detail, particularly, the switched reluctance motor includes a rotor angular position detecting sensor, a plurality of phase coils provided on a stator, a plurality of current sensors which sense the amount of current in the respective phase coils, and an energizing controller. In the energizing controller, on the basis of a target rotational number and the torque of the motor, an energizing initiating rotor angle, a de-energizing terminating rotor angle, and a reference current amount are calculated for each phase coil. When each rotor angular position detected by the corresponding rotor angular position sensor becomes the energizing initiating (energizing terminating) rotor angle position at the corresponding phase coil, the phase coil begins to be energized (de-energized) and between the energizing time point and the de-energizing time point a continual comparison is made between the detected current by the current sensor and the reference current amount for establishing a current supply control wherein if the former is less than the latter or not, the energizing remains unchanged or is stopped, respectively.
In the energizing control in the aforementioned switched reluctance motor, the current to be passed through the phase coil is to be adjusted to the reference current amount, whereby even if a short-circuit occurs in any one of the phase coils, the resultant excess current flowing through the corresponding phase coil is adjusted to the reference current amount and therefore cannot be detected. This means the concept taught by the foregoing Japanese Reference cannot be employed in switched reluctance motors.
SUMMARY OF THE INVENTION
Therefore, in view of the foregoing circumstances, the present invention is intended to provide an apparatus for detecting a short-circuit in a coil of an electric motor such as a switched reluctance motor.
In order to attain the foregoing objects, an apparatus for detecting coil short-circuits in an electric motor is provided which comprises a rotor angular position detecting sensor for detecting an angular position of a rotor, a plurality of phase coils provided on a stator, a plurality of current sensors which sense current amounts in the respective phase coils, an energizing controller calculating an energizing initiating rotor angle, a de-energizing terminating rotor angle, and a reference current amount for each of the phase coils on a basis of the target rotational speed and the torque of the motor, the energizing controller initiating an energization of each of the phase coils when the angular position of the rotor which is detected by the corresponding rotor angular position sensor is found to be in coincidence with the energizing initiating rotor angle, the energizing controller terminating the energization of each of the phase coils when the angular position of the rotor which is detected by the corresponding rotor angular position sensor is found to be in coincidence with the de-energizing initiating rotor angle, the energizing controller making a comparison between the current sensed by each of the current sensors and a reference current during a time duration between the initiation and the termination of the energization of the phase coil, for continuing or interrupting the energization of the phase coil, if the sensed current amount is less or not less, respectively, than the reference current amount, set-up time measuring means for counting a set-up time duration which ranges from a time point at which the sensed current amount is zero to another time point at which the sensed current amount reaches the reference current amount, calculating means for calculating a reference set-up time duration and decision means for deciding whether a short-circuit occurs or not in each of the phase coils based on a comparison between the set-up time duration measured by the set-up time measuring means and the reference set-up time duration.
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patent: 40 35 067 (1992-05-01), None
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patent: 10-42586 (1998-02-01), None
Honma Chiaki
Matsubara Hiroyuki
Sugiyama Masanori
Yamada Daisuke
Yamamoto Keiichi
Aisin Seiki Kabushiki Kaisha
Brown Glenn W.
Hamdan Wasseem H.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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