Patent GB-1103692-A (GB)
Title: Improvements in or relating to the connection of an a.c. generator to a power supply
Inventor: BEDFORD ALAN
IPC: H02J3/42
Filed: 1965-02-26
Abstract: 1,103,692. Synchronizing arrangements. HAWKER SIDDELEY DYNAMICS Ltd. 21 Feb., 1966 [26 Feb., 1965], No. 8425/65. Heading H2H. [Also in Division H3] Synchronizing apparatus for automatically connecting an incoming generator (voltage V 1 , frequency f 1 ) to a main supply (voltage V 2 , frequency f 2 ) comprises:- 1. A voltage matching unit (64), Fig. 4 (1) (not shown) which compares V 1  and V 2  and provides signals K and L if V 1  is respectively below or above a predetermined voltage range including V 2 . The unit controls regulator circuits to bring V 1  into this range, Fig. 2 (not shown). 2. A frequency matching unit (65), Fig. 4 (11) (not shown), which generates two pulse trains at respective frequencies f 1 , f 2  which are fed to a magnetic frequency comparator (95) (see Divisions H3-H5) for production of pulse trains at respective frequencies f 1  f 2  and f 2  - f 1  to raise or lower the speed of the incoming generator. The unit also produces a signal U if f 2  is grester than f 1 . 3. A frequency checking unit (66), Fig. 4 (11) (not shown), which receives the pulse trains f 1  -f 2 , f 2  -f 1  and provides signals T and W if f 1  is respectively within a predetermined range (Œ 0À33 c/s.) including f 2  or outside of this range. If signal K is absent and signal T present, the frequency matching unit (65) generates a pulse train to tend to cause f 1  to exceed f 2  by a predetermined amount (+0À2 c/s.) within the abovementioned range, Fig. 3 (not shown). The frequency checking unit (66) generates a signal Y if f 1  does not exceed f 2  by at least a predetermined amount (0À125 c/s.) which is less than the abovementioned predetermined amount. 4. A phase matching unit (67), Fig. 4 (111) (not shown), which generates two simultaneous signals DD, D<SP>1</SP>D<SP>1</SP> respectively energizing relays (CB1), CB2), closure of whose series-connected contacts initiates action for connecting the generator to the mains. The unit constantly searches for an instant at which the phase angle between the generator and mains voltages is such that, after the expiry of a time interval T from the instant, the angle will be zero, the time interval T being that required to connect the generator to the mains. The signals DD, D<SP>1</SP>D<SP>1</SP> will be generated at such an instant, but one or both signals will be inhibited by the presence of any one of the signals K, L, U, W and Y of a signal EE derived from an inhibit circuit (68). 5. The inhibit circuit (68), Fig. 4 (111) (not shown), generates the signal EE if, at any time, one of the relays (CB1, CB2) is operated and the other relay does not become operated within a predetermined time succeeding the operation of the one relay. The frequency matching and checking circuits may be modified, Fig. 4A (not shown), to provide for synchronizing on to a falling main supply, the signal Y then appearing if f l  is not less than f 2  by at least a predetermined amount, Fig. 3 (not shown), and the signal U appearing if f 1  is greater than f 2 . An automatic start circuit, Fig. 8 (not shown), may control the synchronizing apparatus so that its operation is initiated when the frequency of the incoming generator has reached a predetermined value, the frequency matching unit (65) being used for this purpose. The apparatus is designed to " fail safe " by making the frequency matching and phase matching units as pulseoperated circuits, and by duplicating and interlocking the D.C. circuits used in the apparatus. A typical synchronizing operation of the apparatus is described, Figs. 1, 6 and 7 (not shown). Conventional circuits with solid state elements are employed.