GB575283A - Improvements in or relating to dynamo speed controlling devices - Google Patents

Abstract

575,283. Automatic control systems for dynamos. SELF-CHANGING GEAR CO., Ltd., WILSON, A. G. and MILLER, A. A. March 3, 1943, No. 3507. [Class 38 (iv)] To maintain a suitable speed for a dynamo driven by a variable speed prime mover a variable ratio driving mechanism is included in the drive, as in Specification 562,095 for example, and changes occurring in the electrical circuits and the dynamo due to variation in its speed are caused to introduce a higher speed ratio when the prime mover speed is low. The change may be effected by a solenoid or electrically operated brake, for example of the kind described in Specification 568,409, [Group XXIV], having an operating coil M which is energized by the closing of contacts E of a relay R when, due to a fall in dynamo speed, the current in the field winding F of the dynamo D has been sufficiently increased by the automatic field regulator A. If the two speed ratios are controlled by separate electrical controls back contacts E1 1 on the relay may energize a second solenoid to introduce the lower ratio at higher speeds of the prime mover. In a modification, in which the higher ratio is only made operative when the dynamo speed is low enough to cause opening of the automatic cut-out C, an auxiliary relay coil is connected across the cut-out contacts to assist the coil R. In a further modification, Fig. 3, the relay R controls a second relay, the actuating coil R2 of which is across the cut-out contacts C. This second relay has a retaining coil R3 which is connected through the contacts of both relays and across the battery B. The actuating. coil M may be in shunt or in series with the retaining coil.