GB252731A - Improvements in or relating to dynamo-electric machines - Google Patents

Abstract

252,731. Maschinenfabrik Esslingen. May 28, 1925, [Convention date]. Exciting; dynamos, regulating.-In a constantvoltage dynamo in which the excitation is by means of the combination of the main field with a field produced by currents flowing between shortcircuited brushes, each field pole consists of two parts separately excited to the same polarity by a coil on each part so arranged that with variations in the speed or load, or both the ratio of the magnetizing forces due to 'the coils varies. In the form shown in Fig. 2, the main excitation is given by two coils a, b, the former being connected directly across the main brushes d and the latter across the same brushes but with the inclusion of an iron wire resistance c to maintain the current constant. Fig. 3 shows the arrangement of the coils a, b in slots in the field frame, the slots g opposite the shortcircuited brushes e giving the requisite commutating conditions. Commutating-poles h are provided for the main brushes d. Compensating or compound windings may be provided or a standard exciting winding may be connected across the terminals or in series with either of the coils a, b or with a resistance varying with current or voltage and arranged to assist or oppose the fields due to the current in the windings a and b. The Specification, as open to inspection under Sect. 91 (3) (a), shows a form in which the constant current in the coil b is obtained from an independent battery and it also states that the coils in series with the windings a or b may have their axes in any desired direction. This subject-matter does not appear in the Specification as accepted.