GB669454A - Improvements in or relating to electrostatic machines - Google Patents

Abstract

669,454. Electrostatic machines. CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE. Jan. 23, 1950 [Jan. 21, 1949], No. 1702/50. Class 35. The movable charge carrying conducting members of a Toepler type electrostatic machine are connected in succession to a series of electrical sources so that their potentials are increased by very small steps between the potentials of the machine terminals. This charging process preferably takes place when the capacity between the charge inducing and charge carrying members of the machine is at its maximum. By charging in small steps, the charge carriers are initially charged to increase the machine output, without excessive dissipation of energy due to heavy charging currents. In its simplest form, Fig. 2, the machine comprises a pair of stationary charge inducing plates 1, maintained at a fixed potential by a source 2, and embracing rotatory charge carriers 3, 4 connected to the external circuit by slip-rings and brushes 12, 13. A series of auxiliary generators G1, G2 producing stepped voltages between earth and the terminal voltage of the machme are connected, together with the earth and output terminals, to two groups of contact studs q0, q1, ... q10, and P0, P1, ... P10. Contact arms 14, 15 are connected to the rotary plates 3, 4 and as each is about to move out of the charge inducer 1, the rotor's motion is instantaneously checked while the arm moves over the contacts to charge the carrier in steps from earth potential to the potential of the machine terminal 8. The rorotation is then recommenced to effect a reduction of the capacity between the charge carrier and the inducer 1, and so transfer charge from the carrier to the terminal 8. When the carrier is out of the plates 1, the contact arm reconnects it to earth potential, and the same procedure is repeated for the other charge carrier. This mechanism doubles the output of the machine with little commutation loss. Instead of checking the rotation of the machine for the purpose of the commutation, this latter can be speeded up so as to take place during a small angular displacement of the rotor. In a modification in which very little power is drawn from the commutating generators, a further charge inducer, similar to that indicated at 16 in Fig. 4, and maintained at the machine terminal potential, covers the lower half of the rotor. The generators may be replaced in this case by a series of condensers C1, C2, C3, C4 as shown in Fig. 4. The contact arms 14, 15 are arranged to increase the charge on the charge carrier leaving the inducer 1 and reduce that on the carrier entering the inducer, the charge being alternately taken from and returned to the condensers. In a further modification, not shown, the auxiliary generators or condensers are replaced by an inductance coil forming an oscillatory circuit with the two charge carriers, a commutating switch being provided to connect the charge carriers alternately with the output and earth terminals, and to the inductance, by means of which one plate is charged at the expense of the other as before. In a further modification, Fig. 7, which may be self-exciting as shown or may, in a modified form, employ separate excitation for the inducers 1, 16, the chargecarriers are connected in turn through brushes 27, 28, to conducting segments 29, 30 at output and earth potential respectively, and to a series of short segments 31-36 at intermediate potentials. As the brushes pass over these intermediate segments, commutation is achieved by alternately inter-connecting the charge carriers through a condenser 37 at the outer segments, and directly when on the middle segments. In any of the forms described, commutation may be done by electronic switching and the potentials of the inducing plates may be stabilized by means of additional condensers. Specification 637,434 is referred to.