A power tool is provided including a brushless electric motor, a switching arrangement having motor switches and interposed between the electric motor and a power supply, and a controller configured to control a switching operation of the motor switches for driving the electric motor and enforce a current limit on the current delivered to the electric motor. The controller receives a measure of current passing from the power supply to the switching arrangement and takes corrective action to reduce current delivered to the electric motor if the measured current exceeds the current limit. The controller further receives a signal corresponding to at least one of a type and/or a nominal voltage of the power supply and sets the current limit based on the received signal.

A moving-magnet type linear motor controlling system which can highly accurately control carts even when a plurality of coil units apply forces to the carts is provided. The moving-magnet type linear motor controlling system has: a plurality of coil units having a plurality of coils; a position detecting unit for detecting the positions of the plural carts which are moved along the plurality of coil units; and a controlling unit for determining a ratio of currents which are supplied to the plural coil units on the basis of the positions of the plural carts and an impedance and thrust characteristics of each of the plural coil units.

A control strategy for an electric motor of an electric power assisted steering system of the kind in which a control means produces motor current demand signals that are fed to a motor drive means, the demand signals being dependent on the amount of assistance torque demanded from the motor, the motor drive means being arranged to cause currents to flow in each phase of the motor as required to meet the demanded assistance torque, the control strategy comprising limiting the rate of change of current that is drawn from the electrical supply of the vehicle by the motor in the event that it would otherwise exceed a threshold rate of change.

A multi-motor system includes motor assemblies, each including a motor, a communication circuit to receive a command transmitted from outside, a control circuit to generate a control signal that rotates the motor with a controlled variable that is designated by the command; and a motor driving circuit that causes a current to flow in the motor based on the control signal. The command includes control data indicating the controlled variable of the motor in fixed data length, the controlled variable being expressed at least with an integer, and position-designating data designating a position of the radix point in the control data. The position-designating data is independently determined for each motor assembly.

A motor controlling method includes a step of obtaining an armature magnetic flux, a resultant magnetic flux, a stator current, and a stator voltage, which are represented by a phasor, with respect to an - fixed coordinate system or a d-q rotating coordinate system, a step of calculating an angle () between the stator current and the stator voltage, a step of calculating a torque angle () according to:

=90tan.sup.1[(.sub.s.sub.a sin())/(.sub.a cos())],

where .sub.a indicates a magnitude of the armature magnetic flux and .sub.s indicates a magnitude of the resultant magnetic flux, and a step of controlling the surface permanent magnet motor based on the torque angle ().

A conversion circuit board, including: a microprocessor module; a power module; a communication module; a first interface module; and a second interface module. The microprocessor module is adapted to communicate with a motherboard of an air conditioner via the communication module. The microprocessor module is adapted to connect to a first brushless direct current motor and a second brushless direct current motor via the first interface module and the second interface module, respectively. The power module supplies powers for the microprocessor module, the communication module, the first interface module, and the second interface module.

A motor controller includes an energization pattern determiner that determines an energization pattern that specifies a coil to be energized from coils of multiple phases and a current supply that supplies a current to the coil based on the energization pattern. The energization pattern determiner includes, assuming that an energization period is a time from determination of the energization pattern to determination of the next energization pattern, a first operation mode in which the energization period is determined based on a rotation speed of the rotor, and a second operation mode in which the energization period is longer than in the first operation mode. At the start of activation, the energization pattern determiner passes through multiple energization periods in the second operation mode, and then shifts to the first operation mode.

A motor system provided with one motor and two inverters includes a first inverter control unit which changes a frequency of a first carrier wave (first carrier frequency) used for producing a switching signal fora first inverter according to an operating point of the motor; and a second inverter control unit which changes a frequency of a second carrier wave (second carrier frequency) used for producing a switching signal for a second inverter according to an operating point of the motor. The first carrier frequency has a changing characteristic depending on the first inverter control unit and the second carrier frequency has a changing characteristic depending on the second inverter control unit, and the changing characteristics are different from each other to make the first carrier frequency and the second carrier frequency differ from each other at an identical operating point.

A control unit distributes a motor voltage vector corresponding to an output request for a motor to a first and a second inverter voltage vectors associated with outputs from a first inverter and a second inverter, and determines whether a switching condition for three-phase-on mode is satisfied. Determining that the switching condition is satisfied, the control unit switches to three-phase-on mode in which every high-side switching element or every low-side switching; element of one inverter is turned on and one end of a coil in each phase of the motor is brought into common connection, and the control unit drives the motor with an output from the other inverter. Herein, the switching condition for three-phase-on mode includes failure of one inverter and an inverter voltage vector of an output from one inverter being approximate to 0 when neither of the inverters fails.

A control unit calculates a motor voltage vector including a corresponding excitation voltage command and a torque voltage command in response to an output request for the motor and changes a first inverter voltage vector and a second inverter voltage vector while maintaining the motor voltage vector obtained to allow distribution of the motor voltage vector at any ratio. The first inverter voltage vector includes a first excitation voltage command and a first torque voltage command associated with an output from the first inverter, and the second inverter voltage vector includes a second excitation voltage command and a second torque voltage command associated with an output from the second inverter.