Patent GB-190607891-A (GB)
Title: Improvements in Synchronizing Apparatus for Alternating Current Dynamo Electric Machines
Inventor: MCMAHAN HUGH JOSEPH
Filed: 1906-04-02
Granted: 1906-07-19
Abstract: 7 8 9 1. McMahan, H. J. April 10, 1905, [date applied for under Patents Act, 1901]. Dynamos, synchronizing; motors, synchronizing.- Alternating - current machines are connected in parallel at synchronism by means of a main switch controlled by a normally open circuit, which is closed by a switch, the contacts of which are automatically moved towards each other at a rate varying with the rate at which the machines are approaching synchronism. In the construction of controller shown in Fig. 1, a beam 11 pivoted at its centre is connected through springs 17, 18 to the cores 13, 14 of electro-magnets 15, 16. To the end of the beam which is connected to the core 14 is fixed an angular bracket arm 19 carrying a contactbrush 21, and also the cylinder 20 of a dash-pot, the piston 24 of which is connected through a lever 25, supported on a pivot 26, and a link 30 to an arm 31 loosely mounted on a shaft 32 and provided with a fork 33. The contact-brush 21 co-operates with a contact-strip 38 on a segmental block 34 rigidly mounted on the shaft 32 and provided with a pin 35 located between the prongs of the fork 33. The pin 35 is connected to a hub 36 on the arm 31 by a spiral spring 37, which normally holds the pin 35 against the right-hand prong of the fork 33. One end of the contact-strip 38 is made flush with the surface of the segmental block 34, while at the other end of the strip the block is cut away and a small insulating-block 39 having an inclined surface 391 at its upper end is placed against the strip. The stationary contactmember 40 of the controller is mounted on an arm 41, which is adjustably supported by means of a slot and screw 42. The end of the lever 25, which is connected to the piston-rod 23, is also connected to a post 27 by a spring 28 and an adjustable screw 29. Across the terminals of the alternating- current machines 43, 44, Fig. 3, are connected the primaries 64 of transformers 63, the secondaries 62 of which are connected to the electro-magnets 15, 16 and the mid point of the secondary 59 of the transformer 60. The other terminals of the electro - magnets 15, 16 are connected to the terminals of the secondary 59. When the machines approach synchronism, the switch 45 being closed, the current in the right-hand half of the secondary 59 is augmented by the current induced therein by the primary winding, and the current in the left-band half weakened by the induced current, with the result that the pull of the electro-magnet 15 exceeds that of the electro-magnet 16, rocking the lever 11 and bringing the contact-brush 21 into engagement with the contact-strip 38 and so completing the circuit of the electro-magnet 54, which controls the main switch 46. If the approach to synchronism is slow, the piston 24 is not appreciably raised, but, should the approach to synchronism be rapid, the piston 24 rises, thereby moving the contact-strip 38 forward to meet the contact-brush 21, so that the controller switch is closed just before synchronism is reached, with the result that the main switch is closed at synchronism. Any occasional coincidence of phase when the currents are of widely different frequencies will cause the solenoid 15 to exercise a sudden pull and to rock the block segment 34 to such an extent as to allow the contact 40 to drop behind the shoulder 391, before the contacts 21, 38 come together, so that the main switch under such circumstances will not be closed. In place of the electro-magnet 16, a coil spring may be used, in which case the electromagnet 15 is connected in series with the whole of the secondary 59.