In a three-level chopper apparatus, a protection switch circuit is controllable to change a current pathway through which an overvoltage is applied to a second capacitor or a first capacitor to a current pathway through which no overvoltage is applied to the second capacitor or the first capacitor.

A motor-driven compressor includes an electric motor driven by a motor driver, which includes a switching element that converts DC voltage from a battery to AC voltage. A temperature detector detects the temperature of the switching element. A voltage detector detects DC voltage applied to the switching element from the battery. A control unit suspends the switching operation of the switching element when the detected temperature rises to a temperature threshold. The control unit reduces counter electromotive force generated by the electric motor. The controller changes the temperature threshold such that the temperature threshold gradually increases from when the detected DC voltage is the highest voltage in the applicable voltage range of the battery to when the detected DC voltage is the lowest voltage in the applicable voltage range.

The present invention provides a method and a device for operating an electric machine for a soft changeover from a normal or free-wheel mode to an active short-circuit. To this end, a voltage with which the electric machine is actuated is first reduced in a defined manner to a predefined, preferably very low value and then the phase connections of the electric machine are short-circuited. Excessively high overcurrents, particularly overcurrents greater than the nominal current of the electric machine, can thus be avoided.

The present invention provides a device and a method for changing over an electric machine from the regular operating mode into the open-circuit mode. In order to avoid excessive increases in voltage and associated adverse effects on the electric machine and the other components, in particular batteries, a further control phase is introduced between the end of the regular operating mode and the freewheeling mode, during which further control phase the voltage at the terminals of the electric machine is continuously adjusted from the voltage previously set in the regular operating mode to the expected open-circuit voltage of the electric machine.

Various embodiments include a system having: at least one computing device configured to monitor a dynamoelectric machine having a rotor including an exciter electrically coupled with a field winding, by performing actions including: obtaining measured data indicating a resistance of the field winding at a plurality of rotor angular positions while the rotor is rotating at a speed below one-hundred revolutions per minute; comparing the measured data indicating the resistance of the field winding at the plurality of rotor angular positions with a threshold resistance range; and indicating a potential fault in the field winding in response to determining the measured data indicating the resistance deviates from the threshold resistance range.

A control apparatus includes a first determination section determining whether a power-supply voltage has decreased below a first threshold value, an interruption section interrupting a current flow to an inverter if the voltage has decreased below the first threshold value, a second determination section that determining whether the power-supply voltage has increased above a second threshold value, an interruption releasing section releasing the interruption based on the fact that the voltage has increased above the second threshold value, a count section counting the number of interruptions, a limiting section determining whether the decrease in the power-supply voltage is caused by a first factor of an electric rotating machine or a second factor, and limits the counting if the decrease in the power-supply voltage is caused by the second factor, and a third determination section determining whether the interruption is allowed to be released based on the number of interruptions.

An electrical machine with a rotor or the stator including a plurality of discrete field modules, and the other one of the rotor and the stator including a plurality of armature coils connected to different power converters. Each field module includes one or more field coils which can be activated independent of the field coils of the neighbouring field modules. When at least one of the field coils is inactivated, e.g. because of a defect, each of the power converters is allowing less power to pass through when an armature coil connected to it is moving over an inactivated field coil, and more power to pass through when the armature coil connected to it is moving over an activated field coil.

When the current flowing through each electric terminal of an AC motor 21 reaches the vicinity of zero, an operation putting the electric terminals of the AC motor 21 into an opened state, or putting an electric terminal into a conductive state via a reflux diode inside an inverter 11, is carried out. Herein, as an operation such that the current flowing through each electric terminal reaches the vicinity of zero, the electric terminals are short-circuited by all upper arm or lower arm switching elements of the inverter 11 being turned on. By so doing, a flow of electromagnetic energy of a reactance component of the AC motor 21, from the AC motor 21 into the inverter 11 side when the drive of the inverter 11 is stopped, is prevented or suppressed. As a result of this, an overvoltage or overcurrent is prevented.

A voltage comparator and a programmable counter coupled to a high-speed clock are used to provide a near constant delay time for use in a closed-loop system. The voltage comparator input-output time delay is characterized at a certain temperature and operating voltage then variances in the voltage comparator delay times over a range of operating temperatures and voltages are measured and/or extrapolated. A number of clock pulses used for a delay time count are programmed into the programmable counter to provide for a near constant delay time from a change at the input of the voltage comparator to a change at the output of the programmable counter.

A motor controller for an electric motor includes an enclosure and a processing device, memory device, and communication interface disposed within the enclosure. The processing device is configured to control the electric motor and collect operating information from the electric motor during operation of the electric motor. The memory device is communicatively coupled to the processing device. The memory device is configured to receive and store the operating information collected during operation of the electric motor. The communication interface is communicatively coupled to the processing device and the memory device, and is configured to enable access to the operating information stored on the memory device by a computing device disposed remotely from the electric motor.