Institut Cerac Sa

Atlas Copco Aktiebolag

Erik A Ljung

Carl S Hartwig

Sven H Johansson

C Sverker Hartwig

Erik M Obel

An electrically driven hammer machine comprising a driving piston (103) and a hammer piston (104) driven by the driving piston via a pressure gas cushion (106). The driving piston is driven by a brushless alternating current motor (101) via a crank mechanism (105). A solid state inverter (107) in the power supply conduit (102) supplies power of variable amplitude and frequency to the motor.

Electrically driven hammer machine

A static converter, including at least one pair of mutually co-acting switching transistors (TR1, TR2), of which the first switching transistor (TR1) is controlled with a frequency exceeding the control frequency of the second switching transistor (TR2). A diode (D1, D2) is connected between the emitter and collector of respective switching transistors. The noval feature of the invention resides in that a voltage source (N1, P) is activated when the first switching transistor (TR1) is energized to its conducting mode (I.sub.R) and to supply a reverse recovery current (I.sub.rr) through the diode (D2) of the second switching transistor in the reverse direction of the diode.

Static converter switch with fast recovery freewheel diode

A method and a device for controlling a brushless alternating current motor (23) driven by an inverter (31-36) connected to a direct current supply (24,25). The direct current supplied to the inverter is sensed. The signal is passed through a peak detector (41) to a regulator (45), which decreases its frequency controlling output signal if the peak value input signal exceeds a predetermined value. A control signal corresponding to the torque demand of the motor is also produced. This signal controls the voltage supplied to the motor. Negative pulses at the turning off of the inverter switches are also sensed and used for controlling the degree of magnetization of the motor.

Method and device for controlling a brushless alternating current motor

A method and a means for feeding electric energy to a portable power tool is based on a principle according to which the brushless AC motor of the tool is individually supplied with power from a solid state inverter type power supply by which the amplitude and frequency of the AC current are automatically and individually adapted to the instantaneous load conditions experienced by the motor.

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Stockholm, Sweden

Erik A Ljung