Patent GB-190921357-A (GB)
Title: Improvements in Electric Motor Starting and Speed Controlling Apparatus.
Inventor: HEAP ARTHUR CECIL
IPC: H02K17/30
Filed: 1909-09-18
Granted: 1910-09-19
Abstract: 21,357. Heap, A. C. Sept. 18. [Cognate Application, 22,141/09.] Transformers; polyphase transformers; regulating transformers.-Alternating-current electric motors are started by means which gradually and continuously raise the voltage applied to their terminals. Certain forms of the apparatus can be employed as motor speed regulators. The invention relates to means for connecting any alternating circuit, especially high-tension mains, to a source of supply. It comprises a transformer having a continuously variable ratio, and a switch gear articulated thereto or interlocked therewith, so that the primary winding of the transformer may be connected to the source of supply and the secondary to the motor leads when the transformer ratio is a minimum, and the motor leads directly to the source of supply when the ratio is a maximum. The movable part of the transformer and the switch may be rigidly or elastically connected together in small devices. For example, the secondary of a three-phase transformer is wound on a core with three radial limbs, which core is attached to a shaft carrying switch arms. The primary winding is wound on the alternate limbs of a core ring having six inward radial projections. With the secondary winding in its non-induced position, Fig. 9, the switch arms, which co-operate with segmental faceplate contacts, connect the primary to the source of supply and the secondary to the mains. By means, for example, of a hand-operated worm gear, the shaft is gradually turned, increasing the inductive effect of the primary upon the secondary windings and charging up the mains. The switch contacts are arranged to maintain the original connexions until the fully-induced position of the secondary winding is reached, whereupon the connexions are changed to connect the mains directly to the source of supply, cutting the transformer completely out of circuit. A detent controlled by a " no-volt " coil then holds the shaft against the action of a returning-spring. An overload device is arranged so that the starter will move to its off position should the motor current at any time be excessive. In larger forms of the apparatus, the switch and transformer are separate, interlocking-devices controlling the relative actions of switch and transformer to achieve the above-described results. In one form, the switch is arranged with locking-pieces co-operating with slotted disks geared to the transformer shaft, the locking-pieces yielding in one direction to permit the switch to be opened when in either starting or running position. The switch and transformer may be motordriven with remote control, the switch motor carrying an auxiliary switch upon its shaft for reversing the control connexions at the end of each operation, and the control switch being simply thrown over to complete the connexions for the reverse run. A form of the invention for use with high-voltage circuits is shown in Fig. 9. The main switches G, H are constructed according to Specification 19,005/06. The secondary transformer members are fixed to a shaft carrying three switch arms. These arms carry main switch members S', S<2>, S<3>, and auxiliary members g<6>, h<5>. In the off position, all the switch members are insnlated. To charge the mains, the transformer shaft is turned, and the members S<1>, S<2>, S<3> connect the primary windings P', P<2>, P<3> to the right-hand (dead) contacts of the main switch C, and the secondary windings Q', Q<2>, Q<3> to the right-hand contacts of the switch H, connected to the mains M<1>, M<2>, M<3>. The left-hand contacts and the switch G are connected to the source of supply by leads L', L<2>, L<3>. The switch G is operated in the first position of the starter by a coil g, half of which is then connected between the leads L', L<2> through a segment g<4> on the transformer switch, the auxiliary switch member g<6>, and contact l<2>. The circuit of the coil g is changed as the main switch G closes, the full coil being put in circuit through the contact segment g<5>, auxiliary switch member g<6>, and segment g<4>. Should the switch G be opened from any cause, it can only be closed again by placing the transformer and switch in the initial position. The coil g acts as a " no-volt " coil. When the secondary has become fully induced, the auxiliary switch member h<5> closes the circuit of the coil h of the switch H through contacts m<1>. The switch H is thus closed and couples the leads L', L<2>, L' directly to the mains M<1>, M<2>, M<3>, and the whole of the coil h is placed in circuit between the leads L<1>, L<2>. The circuit-breaker J acts as an overload release. The variable-ratio transformer is shown as having a moving secondary winding and core, but any arrangement may be used in which the disposition of the primary and secondary windings, or the configuration of the magnetic circuit, or a combination of both, can be altered so as to change the inductive relationship of the primary and secondary windings in a continuous, as distinguished from a step-by-step, manner. Figs. 5, 6, and 7 show diagrammatically arrangements in which a magnetic shunt D is moved to vary the amount of the flux from the primary P<1> that shall interlink with the secondary Q<1>. The primary and secondary windings may be in series in some cases.