Patent GB-415701-A (GB)
Title: Improvements relating to plant for the precipitation of dust or other solid particles from an atmosphere
IPC: B03C3/68
Filed: 1933-01-23
Abstract: 415,701. Supply systems; dynamoelectric machines; protective arrangements. PESTARINI, G. M., 4, Tapton House Road, Sheffield. Jan. 23, 1933, Nos. 2197, 12462, and 35266. [Classes 35 and 38 (iv).] Rotary transformers ; insulation ; running generators in series. -The electrodes 2, 3 of dust precipitation plant 1, are supplied from a " metadyne " type rotary transformer or generator arrangement having at least two armature windings S1, S2, P and respective commutators of which the brushes associated with the secondary winding and commutator S1 or S2, or both are connected to the load 1, and the primary brushes P are connected to a low voltage D.C. generator E, means located in the primary circuit being provided for limiting the current from the generator to the primary armature which occurs when the secondary circuit is open. The rotor of the " metadyne " is mounted on the same shaft 9 as that of the generator E and both are driven from a prime mover or motor 10 and the excitation arrangements on the "metadyne " stator may be such that part of the energy in the secondary circuit may be obtained direct from the shaft through torque exerted by the " metadyne." The current limiting means may be a resistance R in series in the primary circuit or a series field winding 8 on the generator E, which, in conjunction with a shunt field winding 7 provides a voltage of falling characteristic at the primary terminals of the " metadyne," or the field winding 8 may be provided on the " metadyne." Alternatively, the generator may be arranged to saturate at a predetermined voltage. The generator may be arranged to have a rising characteristic in order to limit the secondary current on short circuit by providing, in addition to its shunt winding 15, (Fig. 3) an assisting series winding or a winding 16 connected to brushes at right angles to the main brushes on its commutator whose voltage is proportional to the armature cross flux, and in this case, to limit the primary current on open secondary circuit, the generator may be arranged to saturate and a series primary field 19 may be provided on the " metadyne " which opposes the flow of primary current or a series resistance may be provided. In addition, the " metadyne " may be provided with a field winding 20 in series with the secondary circuit so that increase in secondary current produces an immediate tendency to reverse the primary current. The winding 19 is arranged on stator poles diametrically opposite each other whose axis may bisect the angle between the axes of the primary and secondary magnetic fluxes of the rotor, whilst the winding 20 is arranged on a pair of poles at right angles to the poles 19. The winding 19 causes part or all of the power to be transmitted to the " metadyne " directly through the shaft. Where interpoles are provided, the interpole for the primary brushes are energized in series therewith and those for the secondary brushes are energized from across the primary circuit. Where a variator winding is provided which produces a field opposing that due to the secondary current, the secondary interpoles may be provided with an additional winding in series with the variator winding. A number of " metadynes " arrangements may be mounted on a common shaft and the secondaries connected in series to supply the high voltage electrodes. Each secondary is paralleled by a high resistance such as a carbon or silicon rod which is connected to the machine frame at its mid-point. Each " metadyne " may have two or more secondary systems which are connected in series in which case the neutral brush of each '' metadyne " system and one pole of the corresponding generator are connected to the machine frame. The "metadvne" may be connected in series with generators which are not " metadynes " such generators providing up to half the total voltage generated. Three or four " metadyne " systems may be mounted on a vertical shaft with the driving motor at the bottom and insulators separating the machine casings whilst the shaft couplings are of insulating material. The generators for each metadyne " may be on the same shaft or they may be driven from a parallel shaft separately or through gearing. Each set of insulators in a tower is designed to withstand the increment of voltage produced by one " metadyne " arrangement. Where several towers are provided connected in series, the insulation between the driving motor at the base of each tower and the lowest " metadyne " machine must be equivalent to all the insulation in the previous towers. This insulation may be sectionalized by metallic separator connected electrically to corresponding points on the units of the preceding towers so as to provide uniform voltage distribution. This principle may be employed even if the units are mounted on a horizontal shaft. French Specifications 547,855, 623,438, and 637,946, and a publication entitled " Esquisse sur la Metadyne," by G. M. Pestarini in the Bulletin Scientifique A.I.M. No. 4, April 1931, of L'Association des Ingenieurs Electriciens are referred to.