Abstract: A method and apparatus for fault detection of series diodes in rectifiers is disclosed, wherein the voltages across one or both of the individual diodes, and/or the voltage across the pair of diodes are measured to determine a ratio between two of those voltages. The ratio is then analyzed to determine if a fault (e.g., a short circuit or an open circuit) is present. In some embodiments, circuitry can be included to compensate for the normal variations in diode characteristics (e.g., reverse leakage current, reverse recovery charge) between the pair of series diodes to minimize the potential for erroneous fault detection.

Abstract: The invention relates to a method for detecting an overload in an electric hand tool (10) comprising an electric motor (12), in particular a battery-driven electric hand tool (10). According to the invention, an operating current (iB) of the electric motor (12) is determined, the difference (ID) between the value of the operating current (IB) and at least one stored current value (IG) is determined and a thermal overload of the electric hand tool (10) is deduced from said difference (ID). The invention also relates to a corresponding monitoring device (22).

Abstract: A device for controlling a polyphase rotating machine comprising a stator, a rotor, and sensors, the device being capable of receiving at least one first sensing signal (V, W, U) representing a position of the rotor relative to the stator and outputted from a first sensor (16; 18; 14), and a second sensing signal representing the position and phase-shifted relative to the first signal (V, W, U). The second signal is outputted from a second sensor. The control device comprises: means (K, R) for combining the first and the second sensing signals (U, V, W) into a combined signal (Ku; Kv; Kw) including at least one controlled switching signal with a variable cyclic ratio. The combined signal (Ku; Kv; Kw) is based on the cyclic ratio and enables the machine to be controlled.

Abstract: A method of and apparatus for controlling an electric machine. The method can include using a controller to detect whether power is present at a first node of the controller, detect whether power is present at a second node of the controller, generate at least one signal based at least in part on the detection, and energize the electric machine using a detected power when the at least one signal indicates power is present at at least one of the first node, the second node, and a combination of the first node and the second node.

Abstract: A trigger controller for an electric power tool including a motor and a pull-trigger movable along a path having a foremost home position comprises a mechanical switch and a solid-state switch connected in series to the motor, wherein the mechanical switch includes a first moving contact, and the controller includes a second moving contact wherein the first and second moving contacts are movable to operate the mechanical and solid-state switches respectively at different predetermined travelling positions of the pull-trigger from the home position such that the two switches are caused to be initially closed at different times.

Abstract: The present invention relates to a braking system for a DC motor. The braking system includes a current control element placed across the terminals of the DC motor to regulate the magnitude of the electric current generated by the motor when the motor is in a braking mode of operation. In the most preferred embodiment, the current control element includes a semiconductor switch, such as a transistor, that is repeatedly pulsed on and off to act as a controlled short circuit across the armature of the motor. The rotational energy is dissipated as heat by the inherent resistance of the motor windings that may be augmented by an external resistor, if desired. Another possibility is to use a current control element that includes a variable load designed to dissipate the rotational energy in the form of heat. The impedance of the load element is gradually reduced as the speed of the motor is reduced to maintain the rate of energy dissipation near the peak allowable value for the structure of the DC motor.

Abstract: A series wound commutator motor is disclosed which is particularly suited for an inverse-speed electric tool. A switch is provided for switching between a motor operation mode and a braking operation mode, wherein in motor operation at least one field coil is connected in series with an armature winding in a motor circuit fed with a voltage supply and wherein in braking operation the at least one field coil with the armature winding forms a closed braking circuit separated from the voltage supply. A mains-supplied transformer is provided whose secondary winding is connected in the braking circuit parallel to the at least one field coil. A transistor circuit is provided for controlling the current flowing in the braking circuit through the armature winding and the at least one field coil.

Abstract: A brake for a motor, particularly an alternating current motor with an electromagnetic brake is proposed for improving dynamic characteristics without increasing power loss, in which a brake magnet coil is subdivided at an intermediate tap into two partial coils, one of which is arranged in a freewheeling circuit.

Abstract: A level detector outputs signals every time voltages induced by the U-phase, V-phase and W-phase motor coils exceed a predetermined level. When the signals are output in a predetermined order from the level detector, U-phase, V-phase and W-phase commutation circuits supply control signals to U-phase, V-phase and W-phase drive current output circuits, respectively. When the signal outputting order is reversed to the predetermined order, the commutation circuits output no control signals. Upon reception of the control signals from the U-phase, V-phase and W-phase commutation circuits, the U-phase, V-phase and W-phase drive current output circuits supply the currents to the respective motor coils. When at three-phase half-wave motor is rotating in the forward direction, therefore, the currents will be sequentially supplied to the motor coils from the associated drive current output circuits for the individual phases.

Abstract: A control device is provided for an alternating current motor operating in single phase and having first and second windings coupled so that they are shifted in phase with respect to each other. A control unit includes first and second switching elements located between a line connection and respective first and second windings of the motor. One of the switching elements is open and the other closed in a switching state of the control unit, depending on the running direction of the motor. At least one of the switching elements is open when the control unit is in a state of rest. A power supply unit is provided for providing electric energy to the control unit. When the control unit is in a state of rest, the power supply operates by drawing on a first potential difference between a line connection and winding connection associated with the switching element that is open in the state of rest.

Abstract: An AC motor control system and process useful in such AC motor applications as elevators, storage retrieval machines, cranes and hoists, and other load-carrying and work performing machinery.Two identical and electrically isolated windings are utilized in an AC motor with the current to each winding being controlled through an SCR bank. A first winding, when energized, sets up an electromagnetic field which drives the rotor in a clockwise. A second winding, when energized, drives the rotor in a counterclockwise direction.The use of two separate motor windings eliminates line-to-line electrical short circuit problems so that expensive lock-out circuits, circuit breakers, current feedback detectors and air chokes are no longer required.

Abstract: A system for insuring the correct rotational direction of a permanent magnet, bi-directional alternating current motor. A sensor driven by the output of the motor provides a time varying voltage signal that is differentiated and detected. The signal is then applied to either agree with or override the output control signal from a conventional motor control circuit. When the system operates in the correct direction, the signal complements the motor control. When the device tries to operate in an incorrect direction, the signal overrides the motor control signal.

Abstract: A device for changing the rotation of a drill from a forward to a reverse direction which comprises a drill, an AC single-phase motor operatively connected to the drill for driving the same, a circular measuring plate connected to the drill, the circular measuring plate having a handle, and a groove disposed on the periphery of the plate, and a microswitch containing electrical terminals and being operatively connected to the motor, the microswitch containing a bar which is pivotally disposed to engage and disengage the microswitch, the bar having a spring biased arm which extends from the microswitch to slidably engage and rotate with the periphery of the measuring plate, whereby when the handle of the measuring plate is rotated in the left or right direction, the bar of the microswitch is caused to move in a corresponding upward or downward direction along the periphery of the measuring plate, until it engages the slot whereby the direction of rotation of the motor is reversed.

Abstract: An electrical switching circuit for a multi-phase a.c. supply uses semiconductor rectifier switches SCR1 to 5 to reversibly switch power to a multi-phase electric motor so that the motor can be run in a forward or a reverse direction. The SCRs are provided in two sets, one for switching power to forward run the motor, and the other set for reverse running of the motor. Inductor elements .DELTA.L are connected in series with the SCRs. The inductor elements comprise coils which include a non-linear permeability core, for example of ferrite or permalloy, which are operative to suppress voltage transients at switch on of the motor. These transients would otherwise produce spurious firing of the SCRs and could produce a short circuit across the input phases of the a.c. supply. The circuit is used in a valve actuator. Improved torque limit switches and position limit switches are disclosed, which operate a low voltage and which use Reed and Hall effect switches.

Abstract: A synchronous motor having a polyphase armature winding and a field winding is driven by a frequency converter. A position signal associated with the rotational position of the synchronous motor is adapted to be shifted in phase by the maximum of 180.degree. to the advance and lag side by a position control signal, so that a firing pulse for the frequency converter is generated by a combination of a phase-shifted position signal and a reverse signal. Thus the operation modes are switched stably between motoring and regenerative and between forward and reverse operations by changing the magnitude of the phase control signal and reversing the polarity thereof.

Abstract: A system for driving an inductor type synchronous motor for minute control includes an inductor type synchronous motor having first means for driving m numbers of phases and a group of first magnetic teeth, second means equipped with a group of second magnetic teeth; and power feed equipment for feeding power to the driving windings of the individual phases; wherein the minute control characterized by the electrical resolution number R per electrical angle 2m (2m being one fundamental cycle) of the power feed equipment is larger than 3 m points (R.sub.2 3 m) or is stepless; and the power feed equipment feeds electric-waves of current or voltage to the driving windings, the electric-waves being trigonometric functional patterns formed by a control means of the power feed equipment.

Abstract: When a stacker motor slows down before stopping or reversing, it generates an error signal the polarity of which is detected by a sensing circuit which is optically coupled to a motor reversing circuit. If the detected error signal is positive, a first set of LED's in the sensing circuit are illuminated and trigger associated photo-sensitive transistors in the reversing circuit, which in turn energize selected pairs of back-to-back SCR's to connect the lines of a polyphase power source in a "forward" drive direction to the windings of the stacker motor in question, so that the motor is driven in a forward direction. When the error signal is negative, different LED's in the sensing circuit are illuminated and energize different transistors in the reversing circuit so that the motor is driven in the opposite or reverse direction. Inhibiting devices are employed in the reversing circuit to prevent undesirable shorting out of lines upon sudden motor reversal.