| 摘要 |
<p>518,391. Master control of D.C. motors; electromagnetic switches. IGRANIC ELECTRIC CO., Ltd. (Cutler-Hammer, Inc.). Aug. 23, 1938, No. 24844. [Classes 38 (iii) and 38 (v)] A contactor is delayed in closing by associating a condenser in circuit with a restraining winding. Operating coils Mw, la, 2a, 3a of relays M, 1A, 2A, 3A, are energized in turn by movement of a controller C and when the relay M closes a motor A is connected to the supply in series with resistances Rl, R2, R3. Contacts Mx of the relay M also open to disconnect a restraining coil lb on the relay 1A, the relay 1A closes to short-circuit resistance R1 only after a time interval determined by the discharge of a condenser C1 through the restraining coil lb, the condenser being connected in parallel with the coil 1b and charged while the switch Mx is closed. Similarly, the relays 2A and 3A close in timed succession. Where a reversing controller is provided the first resistance relay has its restraining coil connected across the first section of resistance to prevent too rapid closure when " plugging." Each condenser discharge circuit may include an adjustable resistance r, or a single resistance may be provided for all the condensers, the controller C may be replaced by a press-button starter and the operating windings of all relays energized simultaneously. Where a common resistance is provided for the discharge circuit of all condensers an additional resistance in each condenser circuit may be provided. A single condenser may control all restraining windings, the latter being connected in series or parallel and disconnected from the supply simultaneously. In the case of parallel connection, individual discharge resistances for each condenser may be provided in addition to a resistance common to all restraining windings. Instead of connecting the restraining windings initially to the supply, they may be energized and their associated condensers charged from the respective sections of starting resistance. The restraining windings may be sufficiently inductive to contribute in themselves to the timed control. The relays may take the form described in Specification 286,551, [Class 38 (iii)]. As shown in Fig. 8 they may comprise an operating coil a acting on an armature 14 having an extension 13 carrying an adjustable plug 5, the restraining coil b being carried on a core 15.</p> |
