Abstract: A method controls a torque of an a. c. motor which does not cause a shortage of torque by using an economical current detection which estimates d- and q-axis currents Idc, Iqc from d. c. current IDC flowing through an input d. c. bus line of a power converter. A value of d- and q-axis motor currents Id, Iq of a rotational coordinate system are estimated from detected input d. c. current IDC flowing through the bus line of the power converter to which power is input from a d. c. power source 21. A output voltages of the power converter 2 are controlled so that the estimated currents Idc, Iqc are equal to respective current instruction values Id*, Iq*. Errors of motor constants are determined from information on the motor currents and the rotational phase errors by an operation.

Abstract: A method controls a torque of an a. c. motor which does not cause a shortage of torque by using an economical current detection which estimates d- and q-axis currents Idc, Iqc from d. c. current IDC flowing through an input d. c. bus line of a power converter. A value of d- and q-axis motor currents Id, Iq of a rotational coordinate system are estimated from detected input d. c. current IDC flowing through the bus line of the power converter to which power is input from a d. c. power source 21. A output voltages of the power converter 2 are controlled so that the estimated currents Idc, Iqc are equal to respective current instruction values Id*, Iq*. Errors of motor constants are determined from information on the motor currents and the rotational phase errors by an operation.

Abstract: There is provided a control method capable of stably rotating a synchronous motor synchronously with an output frequency even when a phase error between a real rotary axis and a control rotary axis is large. In a phase error operating unit, from the magnitude of the motor current, the magnitude of the motor voltage, the phase difference between the motor current and the motor voltage, and the motor constants, the phase difference between the motor current and the real rotary axis is determined as the first phase difference, and the phase difference between the motor current and the virtual rotary axis is determined as the second phase difference. The difference between the first and second phase differences is defined as the phase error, and the estimation position is so modified as to make the phase error zero.

Abstract: A very high speed permanent magnet type electric rotating machine, in which loss generated on a rotor is small to achieve high efficiency on an air generating source even when driven by an inverter operating at a fundamental frequency of at least several hundreds of Hz and in which a reactor is inserted between the inverter and a permanent magnet type synchronous motor, and content percentages of components of harmonic current supplied to the permanent magnet type synchronous motor are adjusted such that when a content percentage of a fundamental wave is 100%, a content percentage B of a seventh order component is at most 10% and a total content percentage is made equal to or less than a certain value so as to satisfy the relationship (A<C<B) where A is a content percentage of a fifth order component, B is a content percentage of a seventh order component thereof, and C is a content percentage of a ninth order component thereof, thereby enabling realizing a very high speed permanent magnet type electric

Abstract: In a method of accurately estimating the rotor position of a synchronous motor having saliency from observable quantities, a control system for adjusting an output frequency of an inverter on the basis of a value of axis shift of the synchronous motor to operate the motor synchronously with the output frequency is provided with an induced voltage estimating/axis shift operating unit. Currents resulting from conversion of detection currents on a control axis, voltage commands to be inputted to an inverse converter and a speed command are inputted to the operating unit to estimate an induced voltage of the motor 2 and determine the axis shift from a phase of the estimated induced voltage. By using an electrical constant Lq of inductance, a voltage drop across the inductance is determined by the product of a motor speed command and magnitude of motor current. The voltage drop is a virtual quantity that does not depend on the motor rotor position.