An electrical sander structure has a main body, a control mechanism and a control circuit. The main body has a brushless motor, and an electromagnetic coil in the brushless motor has a slotted concentrated winding brushless DC motor design. The control circuit is further includes a power detecting module, a rated power constraint module, an intelligent temperature control protection module and a rotation control module. The brushless motor is able to adjust the speed according to the load variations and intelligent temperature control protection mechanism, maintain the optimal operating efficiency and continuously operate within the power set by the rated power limit. In turn, the brushless motor can operate at optimum operating efficiency, helping to extend the life of the brushless motor, increasing user productivity and reducing energy losses.

A ripple detection device 10 includes: a current detection part 11 that outputs a variation in an armature current as a voltage variation signal; a first smoothing circuit block 12 that extracts a current ripple component and a noise component from the voltage variation signal and outputs a first smoothing signal S1; a gain adjustment part 13 that adjusts the amplitude of the first smoothing signal S1 and outputs an adjustment signal VCA; a second smoothing circuit block 14 that corrects distortion of the adjustment signal VCA and outputs a second smoothing signal S2; a ripple detection part 15 that extracts only the current ripple component from the second smoothing signal S2 by removing the noise component therefrom and outputs a ripple component signal S0; and a digital signal conversion part 16 that converts the ripple component signal S0 into a digital signal.

A brushless direct current motor including a rotor, a first stator disposed adjacent the rotor, and a second stator disposed adjacent the rotor. The first stator is configured to selectively cause a rotational movement of the rotor during normal operation of the motor, and the second stator is configured to selectively maintain a stationary position of the rotor against a force exerted by an external source.

An off-grid power generating apparatus is provided. The apparatus includes an engine, an alternator and an excitation control device. The alternator includes a rotor, a switch and a stator. The switch is movable between a first position and a second position. An output portion of the stator has first and second segments each of which has at least one coil. The first and second segments are operatively and separately connected with the switch. The first and second segments are connected in series at the first position and in parallel at the second position to provide a high voltage and a low voltage respectively. The excitation control device controls the output voltage to make it have a predetermined frequency, and to regulate the engine speed in response to the load power of the engine.

A control system that facilitates energy efficient management of building automation systems is disclosed. The control system comprises a source circuit configured to generate a modulated DC control signal comprising data modulated on a DC source signal having a power associated therewith and a load circuit configured to receive the modulated DC control signal. In addition, the control system comprises a transmission circuit comprising a DC powerline, coupled between the load circuit and the source circuit, and configured to transfer the modulated DC control signal from the source circuit to the load circuit, thereby multiplexing both the power and the data transfer over the DC powerline. In some embodiments, a frequency of the modulated DC control signal comprises a first information associated with the data, and a pulse width of the modulated DC control signal comprises a second, different information associated with the data.

A control system that facilitates energy efficient management of building automation systems is disclosed. The control system comprises a source circuit configured to generate a modulated DC control signal comprising data modulated on a DC source signal having a power associated therewith and a load circuit configured to receive the modulated DC control signal. In addition, the control system comprises a transmission circuit comprising a DC powerline, coupled between the load circuit and the source circuit, and configured to transfer the modulated DC control signal from the source circuit to the load circuit, thereby multiplexing both the power and the data transfer over the DC powerline. In some embodiments, a frequency of the modulated DC control signal comprises a first information associated with the data, and a pulse width of the modulated DC control signal comprises a second, different information associated with the data.

A power generating apparatus is provided. The alternator includes a rotor, a stator, one or more sensors and an electrical circuit. The rotor includes a plurality of symmetric phase windings while the stator has a single phase winding. The excitation control device is configured to control the induced voltage generated in the stator by regulating the rotating magnetic field generated in the phase windings of the rotor. The excitation control device is also configured to regulate the engine speed responsive to calculated load power. The electrical circuit connects the single phase winding of the stator and the load and is configured in a way that the induced voltage generated in the single phase winding and the output voltage applied to the load are at the same frequency. This arrangement reduces costs of the apparatus.

Methods and apparatus providing a smooth transition from a pulse width modulation mode to a linear mode to drive a voice coil motor are disclosed. An example apparatus includes an H-bridge; a pulse generator to generate a pulse when the voice coil motor driver transitions from pulse width modulation mode to linear mode; a first boost circuit to, when the pulse is generated, increase a first current being applied to a first gate of a first transistor in the H-bridge, the increase in the first current enabling the first transistor; and a second boost circuit to, when the pulse is generated, provide an additional path to ground from a node coupled to a second gate of a second transistor of the H bridge, the path to ground corresponding to a voltage drop that disables the second transistor.

A system according to the present disclosure includes a motor driver module and a motor position determination module. The motor driver module is configured to measure current supplied to a motor. The motor position determination module is configured to determine a first position of the motor at a first time when power supply to the motor is initially discontinued based on ripples in the current supplied to the motor during a first period before the first time. The motor position determination module is configured to determine a second position of the motor at a second time when the motor stops rotating after power supply to the motor is discontinued based on the first position of the motor and a rotational speed of the motor at the first time.

Technical solutions are described for applying machine current limiting in permanent magnet synchronous motors. An example system includes a PMSM and a motor control system. The motor control system is configured to receive a torque command and determine whether the torque command can be satisfied based on a given voltage and a given maximum motor current limit. The motor control system is further configured to, responsive to determining that the torque command can be satisfied, determine a minimum current that satisfies the torque command. The motor control system is further configured to send the minimum current as a minimum current command to the PMSM.