Abstract: A method with which stalling of a rotor of a sensor-free motor can be detected is described below. According to one exemplary embodiment, the method comprises operating an electric motor, wherein a rotation speed of the electric motor is controlled by field-oriented control, and wherein an estimate is calculated, wherein the estimate represents magnetic flux in the electric motor. The method further comprises calculating a value which represents the change in the magnitude of the estimate for the magnetic flux and comparing the calculated value with a threshold value in order to detect whether the calculated value lies below the threshold value. An error is flagged if it is detected that the calculated value lies below the threshold value for a specific time.

Abstract: A direct-current to three-phase alternating-current inverter system includes a three-phase motor, a plurality of switching elements, an inverter circuit for the three-phase motor, a capacitor, a direct-current power source and a control circuit. The switching elements arranged in the inverter circuit serve as upper and lower arms for the respective three phases of the three-phase motor, respectively. The capacitor is connected in parallel to the respective pairs of the upper and lower arms. The direct-current power source is arranged between the neutral-point of the three-phase motor and the respective lower arms or the respective upper arms. The control circuit controls the switching elements such that at least the switching frequency of one pair of the switching elements for one phase through which the current having the greatest value flows is lower than the switching frequencies of the other pairs of the switching elements for the other phases.

Abstract: A method for measuring at least one operating variable at multiple electric motors of an automatic parking brake with the aid of a sensor system, the signals generated by the sensor system being processed by a processing device. To minimize the influence of signal interferences, the at least one operating variable is not measured or is not further processed as long as none of the electric motors is activated.

Abstract: A DC to three-phase AC inverter system includes a three-phase motor, an inverter circuit, switching elements, a capacitor, a DC power source and a control circuit. The DC power source is connected to the three-phase motor at a neutral point thereof. The control circuit calculates voltage commands, first through third divided boost commands by dividing a boost command, and first through third drive signals based on the voltage commands and the first through third divided boost commands. The second and third divided boost commands are used when the PWM control is performed by turning on and off the switching elements for the second and third phases while the switching elements for the first phase continues to be on or off state is set larger than those used when the PWM control is performed by turning on and off the switching elements for the first through third phases.

Abstract: In an abnormality diagnosing system for first and second current sensors for measuring a current, an obtaining unit obtains at least one pair of measured values of the first and second current sensors. The at least one pair of measured values is measured by the first and second current sensors at a substantially same timing. A diagnosing unit diagnoses whether there is an abnormality in at least one of the first and second current sensors based on a function defining a relationship between the at least one pair of measured values of the first and second current sensors.

Abstract: An electronic braking device is provided for an asynchronous motor equipped with magnetic bearings of a type used in turbomolecular pumps. The device comprises a circuit for recovering the kinetic energy of the rotor as it decelerates as a result of a disruption of electric current from an external power means. The device is adapted to convert the rotational kinetic energy of the rotor to an electric current and in order to maintain the support provided by the magnetic bearings.

Abstract: An AC electric motor can be braked by applying current pulses to the motor when the polarity of the supply voltage is opposed to the polarity of the back electromotive force (emf) voltage across a stator coil of the motor. This current application continues until the motor has stopped. The stoppage is detected by sensing when the current is being applied during every cycle of the supply voltage. Thereafter, the polarity pattern of back emf voltage induced across each of the motor stator coils is sensed. The occurrence of a back emf voltage polarity pattern that remains unchanged for a given number of cycles is detected. Thereafter, a change in this pattern is sensed and the braking current application either ceases or continues for an additional predetermined interval.

Abstract: A braking direct current (d.c.) (u.sub.g) is injected by way of a diode into at least one of the motor windings at a make time (T.sub.1) which occurs after the tripping of the motor. The make time lies between, at the earliest, a first reference time (T.sub.r1) and, at the latest, a second reference time (T.sub.r2), the braking d.c. voltage (u.sub.g) being substantially equal to a back-voltage (u.sub.r) of the motor winding at the first reference time. The second reference time leads, by 5% of the full periodicity of the network voltage, the first peak in time of the back voltage to occur after the first reference time. The polarity of the braking d.c. voltage (u.sub.g) at the make time (T.sub.1) is opposite to the polarity towards which the back-voltage (u.sub.r) is tending at the first reference time.The braking accuracy of d.c. braked asynchronous motors is improved without increased loading of the motor by relatively heavy currents.

Abstract: An SCR bridge of an elevator speed control apparatus is connected between an induction motor 5 and two (R, S) of the three-phase power supply terminals. Two diagonally opposite legs of the bridge comprise single SCR's 25, 26, and the other two legs each comprise a pair of parallel, reverse polarity SCR's 21, 22; 23, 24. The third power supply terminal is connected directly to the motor through a single switch contact 8. By appropriately controlling the switch contact and the SCR.varies.s in accordance with the difference between the actual and commanded elevator speeds, the bridge can be configured to implement three phase running during acceleration and constant speed modes, single phase running during a transitional slow down mode, and D.C. braking during a deceleration mode.

Abstract: A squirrel cage motor comprises a stator and a rotor, the latter having a pair of end rings and conductor bars interconnecting the end rings, the bars and rings being supported on the rotor core. At least one end ring is provided with at least two insulating gaps to divide that end ring into at least two separate portions. The rotor of the motor can be braked to stop at a predetermined position by applying to the secondary winding of the stator D.C., or A.C. of the same phase as that applied to the primary winding. A three-phase motor can similarly be arranged by providing at least three gaps in at least one end ring.