Patent GB-294971-A (GB)
Title: Improvements in or relating to electric synchronising apparatus
IPC: H02J3/42
Filed: 1927-05-03
Abstract: 294,971. Reyrolle & Co., Ltd., A., Warren, T. R., Jesmond, and Cooke, N. May 3, 1927. Synchronizing dynamo-electric machines.-In controlling the speed of an incoming machine by an auxiliary motor a relay which controls the direction of rotation of the motor is itself controlled so that in one direction of relative rotation of incoming and running machines its contacts remain continuously in one operative position whereas in the other direction the contacts remain continuously in one operative position, so that, for example, a " slow " machine may be rapidly brought to synchronous speed and a " fast " one slowly. The supply of current to the auxiliary motor may be intermittently interrupted in both cases to give an incoming effect to the speed controller and a time-lag relay may increase the amount of interruption at a given part in the approach to synchronous speed. Means controlling the closing of an interconnecting circuit-breaker may be combined with the speed-controlling means and made operative only when the phase difference between the machines remains below a given value for a predetermined time. The arrangement described in Specification 294,970 may be used. In the arrangement shown in Fig. 1, a speed -controlling motor J is reversed by relays H, H<1> according to the position of a contact G<4> of a time-lag lifting relay G. A synchronizing relay C is connected to the mid-point of a resistance C<1> connected between corresponding points of potential transformers A, B on incoming and running machines respectively. This connection is such that the relay is fully energized each time the machines are in phase, but the winding is designed to lift the contents 25‹ before this and to hold them up until 40‹ after. An auxiliary synchronizing relay D is connected between non-corresponding points on the potential transformers A, B; in the case shown one end is connected to the mid-point of a resistance across lagging and leading phases of that of the running machine. Zero excitation of this relay is consequently 30‹ after synchronism on a "fat" incoming machine and 30‹ before on a "slow" one, but the relay is set to lift its contacts 90‹ after its zero excitation and to release them 45‹ before zero excitation. Thus with a " slow" incoming machine the auxiliary relay contacts are open during the period when the synchronizing relay can operate and a " fast " machine only can be synchronized with this arrangement. Whilst accelerating from rest therefore the contacts C<4> remain closed and the contacts G' are held continuously up to cause the motor J to run in a direction which speeds up the machine. The supply to this motor is intermittent since the contact D<4> of the relay D is opened intermittently. An interrupter relay K is energized intermittently by the contact D<4> and as the machine approaches synchronous speed a time lag on this relay becomes ineffective and the contact K<1> opens to increase the period of interruption in the motor current. As soon as the machine begins to over-run the running machine the synchronizing relay C can lift and at synchronism the relays C, D and G being lifted the circuit for the closing coil E<1> of the circuit-breaker is closed at contacts C<3>. D', G<2>. The relay G is short-circuited at C<5> and the contact G<4> moves to the " lower speed " position. The synchronizing relay C remains lifted since a maintaining circuit is closed at C<2>. Should the incoming machine be " fast " when synchronizing is commenced the circuit of relay G will be intermittently broken at C<4> and the contact G<4> will therefore intermittently make the " lower speed " connections for the motor J, not closing on the " raise speed " contact or closing the contact G<2> until the time interval between successive positions of phase equality is sufficient to overcome the time lag on the relay G. In a modification, the relay G is given a time-lag instead of the relay G and itself controls the circuit-breaker. The arrangement shown in Fig. 4 is adapted for selective synchronization of any number of machines L provided with plugs N, N<1> for connecting the appropriate potential transformers and circuit-breaker to the synchronizing apparatus, which includes a switch P disconnecting the last until a synchronizing plug .N has been - inserted on the incoming machine. The synchronizing relay R and auxiliary synchronizing relay S correspond to the relays C, D already described with a " slow " incoming machine, the relay S remains inoperative owing to the setting of the relays R. S, in this case somewhat different to the setting previously described. When the plugs have been inserted the controls of the relay S are intermittently lifted thus interrupting the current to the '' raise-speed " contactor V. When the interval between moments of phase equality has become large enough to make the time-lag on the interrupter U ineffective an increased interruption of motor current will occur. When the incoming machine over-runs the running machine the synchronizing relay R lifts its contacts and the time-lag relay T closes the circuit-breaker coil circuit at T<3>, remaining energized by contact T<2> until short-circuited by the interrupter relay contacts U<1>. If the incoming machine is " fast " when the plugs are inserted the intermittent lifting of the synchronizing relay contact R<4> and the intermittent fall of the relay contact S<4> together' supply current to the lower speed contactor V<1>.