GB173317A - Improvements relating to alternating current generators - Google Patents

Abstract

173,317. Wall, T. F. Sept. 28, 1920. Alternating - current commutator machines; reciprocating-machines; exciting.-An alternating- current generator a particularly adapted for supplying current to the solenoids of reciprocating tools such as rock drills, hammers, and the like is excited from an auxiliary alternator b by a field-magnet winding d the circuit of which is in resonance or approximately so with the frequency of the alternator b. The armature of the main generator a is of the commutator type. In order to ensure the electromotive force and the current in the external circuit periodically reaching zero value at the same or approximately the same instant, a commutator generator f is provided as described in Specifications 5883/15 and 119,546. A circuit-breaker g is included in the external circuit for making and breaking the circuit respectively at the beginning and end of a cycle when the potential difference is at or near zero, and leaving the circuit open for one or more subsequent cycles. A resistance and a condenser may be connected across the circuit-breaker g. The main and auxiliary alternators, the auxiliary commutator generator, and the circuit-breaker may be arranged on the same axis and be driven by a motor i. In a modification instead of using a commutator generator f, a mercury rectifier j, Fig. 2, is provided so that only unidirectional current impulses can be delivered to the solenoids of the tools. A small continuous-current generator k is provided for maintaining the are in the rectifier. Any other rectifier such as an aluminium or other liquid rectifier, or a thermionic or like valve, may be used. The return stroke of the tool plunger may be effected by a spring or by a special solenoid actuated at intervals in a similar manner to the main solenoid. With adjustment of the periodicity of the alternator to suit the rate of operation of the tools the circuit-breaker g may be dispensed with.