A hydraulic fracturing system includes a turbine generator for producing electricity at a well site, the turbine generator producing electrical energy at a voltage. The system also includes an electric pump electrically coupled to the turbine generator and receiving operative power from the turbine generator. The system further includes switch gear arranged between the electric pump and the turbine generator, the switch gear distributing electrical energy from the turbine generator to the electric pump, wherein the voltage remains substantially constant from the turbine generator to the electric pump.

A hydraulic fracturing system includes a turbine generator for producing electricity at a well site, the turbine generator producing electrical energy at a voltage. The system also includes an electric pump electrically coupled to the turbine generator and receiving operative power from the turbine generator. The system further includes switch gear arranged between the electric pump and the turbine generator, the switch gear distributing electrical energy from the turbine generator to the electric pump, wherein the voltage remains substantially constant from the turbine generator to the electric pump.

Provided is an electric drive device which controls a current supplied to coils during normal operation so as to be less than a current limit value when normal, which is determined from heat generating properties and heat radiating properties of a thermally coupled body that includes the coils and an inverter circuit. When an abnormality in each group or each phase of the coils and the inverter circuit is detected, the supply of current to all phases of a group suffering an abnormality in the coils, or to a phase that is not capable of continuous operation, is stopped or reduced; and the limit value of the current supplied to a coil that is capable of continuous operation is reset to a current limit value in the event of abnormality, which is larger than the current limit value when normal, within the range of improvement of the heat generating properties of the thermally coupled body due to the stopping or reduction of the supply of current.

A shortening of an initial diagnosis time is achieved, even after an elapse of a predetermined delay time from an ignition switch being switched to an off-state. After the ignition switch is switched to an off-state after an operation of a control device, which drives an electric motor that applies steering assistance force to a steering system, diagnosis of a power supply circuit that supplies power to the control device is carried out, and a diagnosis item to be implemented in a succeeding initial diagnosis is determined based on a result of the diagnosis.

A method of controlling a portable appliance includes measuring an input current supplied to a motor of the portable appliance and measuring a rotational speed of a shaft of the motor. The method also includes determining a current limit based on the rotational speed of the shaft using a substantially continuous function which relates a domain of rotational speeds to a range of current limits. The method further includes reducing, when the input current exceeds the current limit, the rotational speed of the shaft incrementally along the substantially continuous function until the input current is approximately equal to the current limit.

The invention relates to a method for operating an electric machine (6), and to a control device (10) that is configured to carry out the method. The method comprises a normal mode (ψ.sub.normal) and a special mode (ψ.sub.special) in dependence on a preset target value (M.sub.target), wherein the normal mode (ψ.sub.normal) comprises the steps of detecting an operating state, wherein, in the event that the detected operating state is a special state, the special mode (ψ.sub.special) is carried out. The special mode (ψ.sub.special) comprises the steps of modulating a cyclic value (M.sub.cysl) on the present target value (M.sub.target) and detecting the operating state, wherein, in the event that the operating state is a normal state, the normal mode (ψ.sub.normal) is carried out.

An abnormality diagnosis system configured to diagnose an abnormality of an electric drive system mounted on a mobile body to drive a motor for moving the mobile body, includes: an information acquisition unit configured to acquire a motor output information which is information related to an output state of the motor; an output state determination unit configured to determine whether the output state of the motor is in a low output state that does not contribute to a movement of the mobile body by using the motor output information; and a diagnosis execution unit configured to diagnose an abnormality of the electric drive system when it is determined that the motor is in the low output state.

An abnormality diagnosis system configured to diagnose an abnormality of an electric drive system mounted on a mobile body to drive a motor for moving the mobile body, includes: an information acquisition unit configured to acquire a motor output information which is information related to an output state of the motor; an output state determination unit configured to determine whether the output state of the motor is in a low output state that does not contribute to a movement of the mobile body by using the motor output information; and a diagnosis execution unit configured to diagnose an abnormality of the electric drive system when it is determined that the motor is in the low output state.

A rotary electric machine control device includes multiple drive circuits provided for respective winding sets in a rotary electric machine, and multiple control units. When combinations of the winding sets and configurations provided correspondingly to the respective winding sets are defined as systems, the control units are provided for the respective systems. Each of the control units controls energization of the winding set provided correspondingly, and monitors an abnormality of a monitoring target. Each of the control units performs an abnormality detection time backup control during a period from detection of the abnormality of the monitoring target to confirmation of the abnormality, and performs an abnormality confirmation time backup control when the abnormality is confirmed.

A process for controlling an electric motor includes providing a functional relationship, which associates a first and a second quantity , indicative of a torque delivered by the electric motor and of the supply voltage respectively, with a speed parameter of the electric motor, determining a pair of values of the first and of the second quantity , determining a value of a third quantity indicative of an output speed of the electric motor, determining a value of the speed parameter corresponding to the pair of values determined through the functional relationship, determining a value of a fourth quantity indicative of a difference between the value of the speed parameter and the value of the third quantity, determining a target value for the first quantity as a function of the value of the fourth quantity, and controlling the electric motor according to the determined target value.