There is provided a motor control device which enables torque ripple suppressing control high in followability by executing direct voltage control. A motor control device includes a voltage command calculation unit 15 which calculates a d-axis voltage command value V.sub.d.sup.ref and a q-axis voltage command value V.sub.q.sup.ref from a d-axis current command value i.sub.d* and a q-axis current command value i.sub.q* of a motor 6, a feed forward command value calculation unit 23 which calculates a qi-axis voltage feed forward command value V.sup.qff* for generating a q-axis current ripple on the basis of spatial harmonic parameters and the frequency characteristics of a motor winding, and a subtraction unit 10 which subtracts the q-axis voltage feed forward command value V.sub.qff* calculated by the feed forward command value calculation unit 23 from the q-axis voltage command value V.sub.q.sup.ref calculated by the voltage command calculation unit 15.

This power conversion device comprises: a power converter including a switching element; and a control unit which controls the power converter. The control unit calculates a torque electric current detection value and an excitation electric current detection value from an electric current flowing to an external device, and when an absolute value of the torque electric current detection value is greater than or equal to the excitation electric current detection value, performs control such that the excitation electric current detection value follows the torque electric current detection value.

An outdoor unit includes at least one heat exchanger, a first motor including a first fan, a second motor including a second fan, an inverter that applies voltage to the first motor and the second for respectively, a connection switching unit that switches the voltage applied to the second motor between on and off, and a control unit that controls the inverter and the connection switching unit. The inverter is disposed closer to the first motor than to the second motor.

Described is a method of determining an initial speed of a synchronous motor having a permanent magnet rotor. The method comprises controlling said motor to cause the rotor to rotate or observing that the rotor is rotating. The method includes sensing stator winding currents and transforming the sensed stator winding currents into a two-dimensional (2D) coordinate system using an alpha-beta (α-β) transformation. The rotor angle θ is determined from an arc tangent (Atan) of the ratio of the current in the α-axis to the current in the β-axis. The initial motor speed ω is determined from the determined rotor angle θ.

A motor control method includes the following steps: adjusting a voltage component of an estimated voltage command to a steady-state voltage value; performing a coordinate axis conversion on another voltage component of the estimated voltage command and the steady-state voltage value, and generating a three-phase excitation current to make a synchronous motor rotate to a rotating position and stop; calculating an estimated current signal; calculating an estimated value of the rotating position and adjusting the another voltage component of the estimated voltage command when determining that the current component is not maintained at a steady-state current value; calculating an effective inductance of the synchronous motor based on the steady-state voltage value, the another voltage component of the estimated voltage command, the steady-state current value, and another current component of the estimated current signal when determining that the current component is maintained at the steady-state current value.

Saliency tracking for brushless direct current (BLDC) motors and other permanent magnet synchronous motors (PMSMs) is provided. Embodiments generate an accurate estimate of rotor position for use in field-oriented control (FOC) of BLDC motors. In addition, a robust saliency tracking algorithm provides for the use of BLDC motors in low-speed high-torque applications without the need of external sensors. This enables sensorless application of higher level algorithms as well, such as servo control. In addition, accurate measurement of motor phase inductance and flux linkage can be provided without any additional equipment.

A controller for an electric motor comprises: an estimator configured to estimate a position of a rotor by using a d-axis current, a q-axis current, a d-axis voltage command value, and a q-axis voltage command value from which a noise is removed by a filter having a first time constant when a torque command value is equal to or greater than zero, and estimate a rotational speed of the electric motor and the position by using the d-axis current, the q-axis current, the d-axis voltage command value, and the q-axis voltage command value from which a noise is removed by a filter having a second time constant smaller than the first time constant when the torque command value is less than zero

A parameterless and position-sensorless MTPA control of a permanent magnet synchronous motor including: using three rotating reference frames having different observation angles to parse the current vector; using a target current value and a preset current-rotor angle y that is between the current vector and the q.sub.r-axis of the (d.sub.r, q.sub.r) rotor reference frame to obtain the angles between the current vector, the voltage vector, and the rotor position; obtaining the target voltage value and the target voltage angle by using the obtained angles to obtain the target phase voltage values for regulation. The method is simple in controlling the motor, improves the control efficiency and reliability, and improves the control accuracy.

A parameterless and position-sensorless MTPA control of a permanent magnet synchronous motor including: using three rotating reference frames having different observation angles to parse the current vector; using a target current value and a preset current-rotor angle y that is between the current vector and the q.sub.r-axis of the (d.sub.r, q.sub.r) rotor reference frame to obtain the angles between the current vector, the voltage vector, and the rotor position; obtaining the target voltage value and the target voltage angle by using the obtained angles to obtain the target phase voltage values for regulation. The method is simple in controlling the motor, improves the control efficiency and reliability, and improves the control accuracy.

Using an update amount, an update amount calculating circuit manipulates a phase-control angle so as to perform feedback control such that a steering torque corresponds to a target torque. The steering torque is obtained by reducing a steering torque in magnitude by a predetermined value. The phase-control angle is used to convert a current command value to a value of a fixed coordinate system, for example. Using a guard value, a guard processing circuit performs a guard process on a current command value set by a command value setting circuit, so that the current command value becomes the current command value. The guard value is used to determine an appropriate range for a variation in the current command value in accordance with an amount by which the steering torque exceeds in magnitude the target torque.