A unique system may include a power absorber; an electrical machine coupled to the power absorber and operative to supply mechanical power to the power absorber; a drive coupled to the electrical machine and operative to supply electrical power to drive the electrical machine; and a controller communicatively coupled to the drive. The controller may be configured to execute program instructions to selectively vary a control voltage while maintaining a given torque output of the electrical machine, and to determine, based on varying the control voltage, a minimum current required for the electrical machine to maintain the given torque output.

A method of a control system (2200) controls an inductance motor in a blower including an impeller and volute using a pressure compensation control system. The control system may be implemented in a respiratory pressure therapy device. The control system may include a sensor configured to provide a pressure signal indicative of the pressure of a flow of fluid produced by the blower. A measured pressure may be compared to a set pressure to determine a pressure error. A slip frequency may be adjusted as a function of the pressure error in an attempt to eliminate or minimise the pressure error.

A method may include transmitting an excitation signal from a stator of a motor to a rotor of the motor, where the excitation signal is received at a set of rotor windings, and where the excitation signal produces a rotating magnetic flux at the rotor that generates a first alternating current (AC) voltage at a set of stator windings. The method may further include controlling the excitation signal to equalize and synchronize the first AC voltage to a second AC voltage at an AC bus. After the synchronization, the method may also include electrically connecting the set of stator windings to the AC bus. The method may include reducing an amplitude of the excitation signal to enable current flow from the AC bus to the set of stator windings, thereby generating torque that results in rotation of the rotor.

The present disclosure is directed to a hydraulic fracturing system for fracturing a subterranean formation. In an embodiment, the system can include an electric pump fluidly connected to a well associated with the formation, and configured to pump fluid into a wellbore associated with the well at a high pressure so that the fluid passes from the wellbore into the formation and fractures the formation. The system can further include one or more ancillary units associated with the fluid pumped into the wellbore. The system can further include a first motor electrically coupled to the electric pump to operate the electric pump, and one or more second motors, each of the second motors electrically coupled to each of the ancillary units to operate the one or more ancillary units.

This invention provides a frequency converter and bypass frequency conversion control system, and its switching control method, belonging to the technical field of motor drive control. The frequency converter of this invention accesses a network voltage signal with a corresponding first frequency and first phase, wherein the frequency converter is configured to be able to operate in tracking and synchronization mode, and in tracking and synchronization mode, the frequency converter tracks the first frequency and first phase of the network voltage signal in order to basically synchronize the second frequency and second phase of its output voltage signal with the first frequency and corresponding first phase of the network voltage signal. The frequency converter of this invention achieves simple, low cost, fast synchronization with good synchronism.

A thyristor starter is configured to accelerate a synchronous machine from a stop state to a predetermined rotation speed by sequentially performing a first mode of performing commutation of an inverter by intermittently setting DC output current of a converter to zero and a second mode of performing commutation of the inverter by induced voltage of the synchronous machine. In a first case in which a first synchronous machine having a first inductance is started, a switching rotation speed for switching from the first mode to the second mode is set to a higher rotation speed, compared with a second case in which a second synchronous machine having a second inductance larger than the first inductance is started.

Subsea power supply assembly supplying electric power to a motor at a second location from a first location. The subseas power supply assembly includes a variable speed drive (VSD) and a step-up transformer connected to it. At a subsea location the assembly includes a first step-down transformer with input and output and an uninterruptible power supply having an input. A step-out cable supplies power from the step-up transformer to the motor. The cable connects to the first step-down transformer. The speed of the electric motor is proportional to the output frequency of the VSD. The power receiving input of the uninterruptible power supply connects to the output of the first stepdown transformer, thereby receiving electrical power with frequency equal to the output frequency of the VSD.

A method for determining at least one property of a rotational movement of a three-phase rotary current machine in generator operation, with an electrical parameter for a phase voltage of the relevant phase of the three-phase alternating voltage of the rotary current machine generated in generator operation being continuously recorded metrologically for each of the three phases. Three electrical parameter pairs are formed from the three electrical parameters, whereby the three electrical parameter pairs respectively include electrical parameters of a first and a second phase, electrical parameters of the second phase and a third phase, and electrical parameters of the third phase and the first phase. A sign of a difference between the electrical parameters of each parameter pair is continuously determined. The property of the rotational movement is determined from change times corresponding to times of immediately successive sign changes of the differences between the three parameter pairs.

A fan drive circuit for a variable speed fan motor in a cooling system, includes an inverter configured to supply a current signal to stator windings of the variable speed fan motor, a frequency detection circuit coupled to an output stage of an inverter of a compressor motor of the cooling system and configured to detect a first frequency of a compressor current signal at the output stage of a variable speed compressor drive circuit and generate a frequency signal, and a digital signal processor (DSP) coupled to the inverter and the frequency detection circuit. The DSP is configured to receive the frequency signal corresponding to the first frequency from the frequency detection circuit, select a second frequency corresponding to the first frequency at which to operate the variable speed fan motor, and transmit control signals to the inverter to supply current to the stator windings at the second frequency.

Motor controllers and methods for controlling drive circuit bypass signals are provided. The motor controller includes a drive circuit configured to generate variable frequency power based on input power received from a power source, and a drive contactor coupled between an output of the drive circuit and the motor. The drive contactor is configured to couple the drive circuit to the motor when a drive enable signal is received from an external controller, and decouple a line power enable signal from a line contactor by the external controller based on a presence of the drive enable signal. The line contactor is configured to couple the motor directly to the power source when the line power enable signal is received by the line contactor.