A control method of a motor rotation speed may include calculating a q-axis potential difference of a synchronous coordinate system for controlling a q-axis current of the synchronous coordinate system based on a target rotation speed of a motor and a measured rotation speed value of the speed sensor, calculating a voltage command of the synchronous coordinate system based on the calculated q-axis potential difference of the synchronous coordinate system, and controlling an inverter connected to the motor according to the calculated voltage command of the synchronous coordinate system.

A motor control device controls an induction motor driving a spindle of a machine tool, and includes: a spindle control unit that controls a rotational position or rotational speed of the spindle, and a secondary magnetic flux of the induction motor in accordance with an operation command based on an operation program of the machine tool; an advance detection unit that pre-reads the operation program, and detects a change in the operation command requiring to increase the secondary magnetic flux of the induction motor in advance; and an advance change unit that causes the secondary magnetic flux of the induction motor to increase prior to a change in the operation command in the spindle control unit, in a case of a change in the operation command being detected by the advance detection unit.

A motor control device controls an induction motor driving a spindle of a machine tool, and includes: a spindle control unit that controls a rotational position or rotational speed of the spindle, and a secondary magnetic flux of the induction motor in accordance with an operation command based on an operation program of the machine tool; an advance detection unit that pre-reads the operation program, and detects a change in the operation command requiring to increase the secondary magnetic flux of the induction motor in advance; and an advance change unit that causes the secondary magnetic flux of the induction motor to increase prior to a change in the operation command in the spindle control unit, in a case of a change in the operation command being detected by the advance detection unit.

A control system for an electric machine, wherein the electric machine has a maximum bus value (V.sub.bus) is provided. The control system is configured to determine a feedforward vector (V.sub.FF), determine a feedback vector (V.sub.FB), compare a magnitude of a sum of the feedforward vector and feedback vector (|V.sub.FF+V.sub.FB|) and the maximum bus value (V.sub.bus), when |V.sub.FF+V.sub.FB|<V.sub.bus providing a control vector of V.sub.FF+V.sub.FB to the electric machine, and when |V.sub.FF+V.sub.FB|>V.sub.bus providing a control vector of V.sub.FF+k(V.sub.FB) to the electric machine, where k is a scalar value between 0 and 1 inclusive where |V.sub.FF+k(V.sub.FB)|=V.sub.bus.

A control system for an electric machine, wherein the electric machine has a maximum bus value (V.sub.bus) is provided. The control system is configured to determine a feedforward vector (V.sub.FF), determine a feedback vector (V.sub.FB), compare a magnitude of a sum of the feedforward vector and feedback vector (|V.sub.FF+V.sub.FB|) and the maximum bus value (V.sub.bus), when |V.sub.FF+V.sub.FB|<V.sub.bus providing a control vector of V.sub.FF+V.sub.FB to the electric machine, and when |V.sub.FF+V.sub.FB|>V.sub.bus providing a control vector of V.sub.FF+k(V.sub.FB) to the electric machine, where k is a scalar value between 0 and 1 inclusive where |V.sub.FF+k(V.sub.FB)|=V.sub.bus.

The invention relates to a method for operating an electric machine (2) comprising a rotatably mounted rotor and a motor winding that is electrically connected to an electrical energy store (4) by means of a power electronics (3). In said method, the machine (2) and/or an apparatus comprising the machine (2) is/are monitored in respect of fault events, and the motor winding is short-circuited by triggering the power electronics (3) upon detection of a fault event. According to the invention, a desired trajectory (T) for an actual current vector (i.sub.actual,dq) of an electric motor current flowing through the motor winding is ascertained, said desired trajectory (T) extending from a current actual working point (AP1) of the machine (2) to a short-circuit working point (AP2) of the machine (2), a pilot control action is predicted according to the desired trajectory (T), and the power electronics (3) are triggered to short-circuit the motor winding according to the pilot control action in such a way that when the motor winding is short-circuited, a curve (V) of the actual current vector (i.sub.actual,dq) at least substantially matches the desired trajectory (T).

The invention relates to a method for operating an electric machine (2) comprising a rotatably mounted rotor and a motor winding that is electrically connected to an electrical energy store (4) by means of a power electronics (3). In said method, the machine (2) and/or an apparatus comprising the machine (2) is/are monitored in respect of fault events, and the motor winding is short-circuited by triggering the power electronics (3) upon detection of a fault event. According to the invention, a desired trajectory (T) for an actual current vector (i.sub.actual,dq) of an electric motor current flowing through the motor winding is ascertained, said desired trajectory (T) extending from a current actual working point (AP1) of the machine (2) to a short-circuit working point (AP2) of the machine (2), a pilot control action is predicted according to the desired trajectory (T), and the power electronics (3) are triggered to short-circuit the motor winding according to the pilot control action in such a way that when the motor winding is short-circuited, a curve (V) of the actual current vector (i.sub.actual,dq) at least substantially matches the desired trajectory (T).

An induction machine includes a stator and a rotor, wherein a stator winding is arranged within the stator, a control device controls a converter such that the converter connects the stator winding to a power-supply network such that a stator current flows within the stator winding, and the stator current has a field-forming current component and a torque-forming current component, where the control device controls the converter such that, during load periods, a torque acts between the stator and the rotor, controls the converter during periods of rest such that a torque acts between the stator and the rotor, controls the converter at least at the beginning of the periods of rest such that the field-forming current component has a nominal value, and controls the converter during the load periods such that the field-forming current component has a lower value than the nominal value.

An induction machine includes a stator and a rotor, wherein a stator winding is arranged within the stator, a control device controls a converter such that the converter connects the stator winding to a power-supply network such that a stator current flows within the stator winding, and the stator current has a field-forming current component and a torque-forming current component, where the control device controls the converter such that, during load periods, a torque acts between the stator and the rotor, controls the converter during periods of rest such that a torque acts between the stator and the rotor, controls the converter at least at the beginning of the periods of rest such that the field-forming current component has a nominal value, and controls the converter during the load periods such that the field-forming current component has a lower value than the nominal value.

Provided is a power conversion device for suppressing a variation amount of a bus current to decrease a power loss in consideration of control of detecting the bus current during operation. In control by a power conversion part in accordance with a switching signal, a voltage vector is caused to bring a mode into a power running mode at a timing of detecting the bus current when an AC rotating machine is in a power running operation state, and the voltage vector is caused to bring the mode into a regeneration mode at a timing of detecting the bus current when the AC rotating machine is in a regeneration operation state, thereby decreasing the power loss due to the variation in the bus current.