A power conversion device includes a high-pass filter for extracting an AC component of voltage Vdc of a DC link section, a multiplier for multiplying output VdcAC of the high-pass filter by a first gain K1 and outputting the result, a multiplier for multiplying output of the multiplier by a second gain K2 and outputting the result as a d-axis voltage correction signal vdcmp*, and a multiplier for multiplying output of the multiplier by a third gain K3 and outputting the result as a q-axis voltage correction signal vqcmp*. The gate signal generation section generates gate signals on the basis of a signal vd1 obtained by adding the d-axis voltage correction signal vdcmp* to a d-axis voltage command value vd* and a signal vq1 obtained by adding the q-axis voltage correction signal vqcmp* to a q-axis voltage command value vq*.

A power conversion device includes a high-pass filter for extracting an AC component of voltage Vdc of a DC link section, a multiplier for multiplying output VdcAC of the high-pass filter by a first gain K1 and outputting the result, a multiplier for multiplying output of the multiplier by a second gain K2 and outputting the result as a d-axis voltage correction signal vdcmp*, and a multiplier for multiplying output of the multiplier by a third gain K3 and outputting the result as a q-axis voltage correction signal vqcmp*. The gate signal generation section generates gate signals on the basis of a signal vd1 obtained by adding the d-axis voltage correction signal vdcmp* to a d-axis voltage command value vd* and a signal vq1 obtained by adding the q-axis voltage correction signal vqcmp* to a q-axis voltage command value vq*.

A handheld AC power tool is provided. The power tool is comprised generally of: a brushless DC motor; a power cord connectable to an AC power socket; a converter circuit configured to receive input power from the power cord and operable to output a DC bus voltage, a switching arrangement interposed between the electric motor and the converter circuit; a motor drive circuit interfaced with the motor switches; and a power switch operable by a user to selectively energize the motor drive circuit and thereby power on the tool. The converter circuit includes a rectifier and a capacitor electrically coupled across the rectifier, such that the capacitor has capacitance sized to produce a DC bus voltage whose magnitude from an AC power source is substantially same as magnitude of voltage from a DC power source.

A handheld AC power tool is provided. The power tool is comprised generally of: a brushless DC motor; a power cord connectable to an AC power socket; a converter circuit configured to receive input power from the power cord and operable to output a DC bus voltage, a switching arrangement interposed between the electric motor and the converter circuit; a motor drive circuit interfaced with the motor switches; and a power switch operable by a user to selectively energize the motor drive circuit and thereby power on the tool. The converter circuit includes a rectifier and a capacitor electrically coupled across the rectifier, such that the capacitor has capacitance sized to produce a DC bus voltage whose magnitude from an AC power source is substantially same as magnitude of voltage from a DC power source.

In a method of operating a drive device, a sound signal is generated as a function of at least one operational and/or state variable. An electric machine of the drive device is hereby as a sound generator to output the sound signal. The sound signal can be determined from a time gradient of the operational and/or state variable.

In a method of operating a drive device, a sound signal is generated as a function of at least one operational and/or state variable. An electric machine of the drive device is hereby as a sound generator to output the sound signal. The sound signal can be determined from a time gradient of the operational and/or state variable.

An electronically commutated motor is operated from a DC voltage source (U.sub.B), e.g. from a DC link circuit (46). The motor has a permanent-magnet rotor (28) and a stator having a stator winding strand (26) in which, during operation, an alternating voltage is induced by the permanent-magnet rotor (28). It further has an H-bridge circuit (22) having power semiconductors (T1 to T4). At the beginning of a commutation operation, the presently conductive semiconductor switch of a first bridge half (38) is switched off, in order to interrupt energy delivery from the DC voltage source (U.sub.B), so that, in the other bridge half (56), a loop current (i*; −i*) flows through the stator winding strand (26), through the semiconductor switch still controlled to be conductive therein, and through a recovery diode (58; 60) associated with the blocked semiconductor switch of that other bridge half. This loop current converts the energy stored in the magnetic circuit of the motor (20) at least partly into driving energy for the permanent-magnet rotor (28), and in that context the stored energy drops to zero. This currentless state of the stator winding strand (26) is detected in a sensorless manner by measuring the voltage (u.sub.ind) induced by the rotor (28) in the stator winding strand (26).

An electronically commutated motor is operated from a DC voltage source (U.sub.B), e.g. from a DC link circuit (46). The motor has a permanent-magnet rotor (28) and a stator having a stator winding strand (26) in which, during operation, an alternating voltage is induced by the permanent-magnet rotor (28). It further has an H-bridge circuit (22) having power semiconductors (T1 to T4). At the beginning of a commutation operation, the presently conductive semiconductor switch of a first bridge half (38) is switched off, in order to interrupt energy delivery from the DC voltage source (U.sub.B), so that, in the other bridge half (56), a loop current (i*; −i*) flows through the stator winding strand (26), through the semiconductor switch still controlled to be conductive therein, and through a recovery diode (58; 60) associated with the blocked semiconductor switch of that other bridge half. This loop current converts the energy stored in the magnetic circuit of the motor (20) at least partly into driving energy for the permanent-magnet rotor (28), and in that context the stored energy drops to zero. This currentless state of the stator winding strand (26) is detected in a sensorless manner by measuring the voltage (u.sub.ind) induced by the rotor (28) in the stator winding strand (26).

An electric power system including a front-end converter that is supplied electric power from a high-voltage DC power source, and an associated motor control system is described. A control method includes monitoring the electric machine and determining a reference current based upon the electric power supplied from the high-voltage DC power source. A motor current is determined based upon the monitoring of the electric machine, and a feed-forward current is determined based upon the motor current and the monitoring of the electric machine. A first duty cycle is determined based upon the reference current, the motor current and the feed-forward current, and a feed-forward duty cycle is determined based upon the monitoring of the electric machine. A second duty cycle is determined based upon the feed-forward duty cycle and the first duty cycle, and the front-end converter is controlled based upon the second duty cycle.

An object of the invention is to reduce a torque pulsation. A control device of a rotary electric machine according to the invention includes a sinusoidal wave generation circuit which generates a sinusoidal wave signal according to a magnetic pole position of a rotor of the rotary electric machine, a current command circuit which generates a speed command, a torque command based on actual speed information, and a current command on the basis of the sinusoidal wave signal, and a current control circuit which controls an inverter circuit interposed between a stator winding and a DC power source to make a sinusoidal current flow to the stator winding on the basis of the current command and a current detection signal of the stator winding of the rotary electric machine, wherein the current control circuit periodically changes a current phase of the sinusoidal current when the rotary electric machine is driven by a predetermined torque and a predetermined rotation frequency.