Electricity: single generator systems – Miscellaneous
Patent
1982-12-27
1986-12-09
Hickey, R. J.
Electricity: single generator systems
Miscellaneous
307 87, H02J 308
Patent
active
046282467
DESCRIPTION:
BRIEF SUMMARY
The object of the invention is to soft couple AC mains, preferably, of asynchronous windmill generators.
The general coupling method used today is a direct or one stage coupling of the generators to the AC mains by three-phase contactors at a speed equal or close to the generator's synchronous speed. Such coupling will set up a direct current in at least two of the phases, with the direct current sitting up a static magnetomotive force in the generator's air gap. At the same time, currents will be induced in the rotor, even if the generator runs synchronously. The field which is set up by the rotor currents will, together with the static field, create strong torque pulsations which can make the entire rotary system hunt violently, with a harmful effect on shafts, gear unit, and mill arms. The coupling method also results in heavy voltage drops in the mains which may disturb local consumers.
The invention is characterized in that the sequential coupling of the single phases, especially the first power-producing coupling and short-circuit of any series impedances, is made around the respective voltage maxima of the contacts used for the purpose before coupling.
Such phase voltage control has not been established in the known designs of sequential couplings.
Compared to the known technology, the result is a considerable reduction in both coupling surges and torque changes since the direct current transients can be kept at a reasonable minimum during coupling at times of phasic voltage maxima.
FIG. 1 shows a coupling made with external shortable series impedances, which coupling applies to both star and delta-wound stators;
FIG. 2 is a coupling member corresponding to FIG. 1, with a star-wound stator and a separate neutral point brought out;
FIG. 3 shows a delta-coupled generator with shortable series impedances internally in the delta coupling;
FIG. 4a shows a phase rotation module (A) for phase control of semiconductor contactors;
FIG. 4b shows the diagrammatic construction of the phase rotation module (A);
FIG. 5a shows a time lag module (B);
FIG. 5b shows the diagrammatic construction of a time lag module (B);
FIG. 6 shows an activation module (C) for semiconductor contactors;
FIG. 7 shows a contact arrangement made with series impedances and based on semiconductor contactors;
FIG. 8 shows a simplified diagram of the entire arrangement.
Referring now to the drawings wherein like reference numerals are used through the various views to designate like parts and, in a three-phase generator such as shown in FIG. 1, the windings (not shown) can be either star or delta-coupled, with two contact connections 1 and 4, 2 and 5, and 3 and 6, respectively emanating from each of the three generator terminals; 1, 2, and 3 of these contacts being connected to the AC mains via impedances of a purely ohmic or ohmic/inductive nature 7, 8, and 9, while contacts 4, 5, and 6 are connected direct to the AC mains.
FIG. 2 shows the same contact and series impedance arrangement as used in FIG. 1, but the generator, which is shown in star coupling, has a neutral point brought out.
FIG. 3 shows generator windings with internal contact and series impedance arrangements which on the surface are in the form of delta coupling.
When soft coupling is aimed at, contacts 1, 2, and 3 coupled to the series impedances are closed sequentially, whereafter contacts 4, 5, and 6 placed over series impedances 7, 8, and 9 are closed sequentially so that direct coupling to the AC mains is established.
In FIG. 4a the module receives, via U.sub.st terminals, the phase AC voltage from one of the contacts 1-6 as long as it is open and emits a phase-controlled closing signal as logic signal "1" across terminal U.sub.out when a logic signal "1" is received across terminals U.sub.go.
In FIG. 4b, the phase input U.sub.st is fed via an isolating transformer across an R.C. phase rotation link to an operator amplifier whose square voltage output is supplied via a diode to two one-shot generators, one of which is triggered on a rise in signal voltage, while the o
REFERENCES:
patent: 3069556 (1962-12-01), Apfelbeck et al.
patent: 3493778 (1970-02-01), Cutler et al.
patent: 3794846 (1974-02-01), Schlicher et al.
patent: 4256972 (1981-03-01), Wyatt et al.
patent: 4322630 (1982-03-01), Mezera et al.
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