| GB831967A | 1960-04-06 | |||
| GB1192861A | 1970-05-20 | |||
| DE1196776B | 1965-07-15 | |||
| EP0469263A2 | 1992-02-05 | |||
| CH125570A | 1928-04-16 | |||
| GB345137A | 1931-03-19 |
125 Claims
1) Asyncronuos generator for variable speed prime movers comprising two asynchronous motors (a,b) squirrel-cage type, rigidly coupled by the shafts, with the bushing (c); the case of motor (a) is fixed to the base (t) and the statoric winding (d) ■
130 connected to a three-phases power grid; the case of the second motor (b), free to turn around the shaft (c), presents a shaft (m) driven by a prime mover, being the statoric winding (d 1 ) i, 3 connected to the same power grid by means of a slip rings (e)
collector and the brushes |s). => . , ■■ -, ■ '■ :>,: ' - -v.>~ :d .. VγU severs
135 2) - - Asynchronous generator for : variable speed prirne movers characterized by a compact ■ embodimentn-Fig,: 2,, where; the statoric winding (a,a') is .cqnnected to a three-phases power : .grid
-, ■ ; at which also the rotoric winding (b,b') is. connected, equivalent to the statoric winding (a,a' ( ).ιcThe second one is relative to a rotor
140 with the shaft rigidly connected to; the prime mover. Between ftq ■
, ■■ stator and the rotor is allocated an hollow. ferromagnetic rotpr . with two squirrel cages^iraner and outer the core, free to turn at
13ξ idle state around the sha%(rn) supported by, rolling bearings, ,(p), provided that the cylindriicabputWard surface, of the core aπcl the
145 relative squirrel cage interact- ^through the . air-gap (»u'). : with , the, stator (a) and the cylindrical inward surface of the core and the relative squirrel cage infract through the , air-gap (u") withςthe
1 J0 rotor (b). 150 3) Asynchronous generator for variable speed prime movers, according to claims 1 and 2, characterized in that the synchronous speed reached by idling rotor (c) when the machine is connected to a power grid involves that the shaft (m) of the rotor (b) stands still and when the shaft (m) driven by a prime
155 mover starts to rotate, the generator supplies power to the power grid even at low rotation speeds.
4) Electric generator, connected to a three-phases power grid, driven by variable speed prime movers characterized in that it can supply electric power rotating in both directions. |
"TWIN VARIABLE SPEED ASYNCRONOUS GENERATOR"
Description
The present patent request for industrial creation concerns a variable speed electric generator grid connected, designed to deliver the generated electric power to a three-phases power grid, starting from irregularly variable mechanical energy sources. This generator delivers the power to the grid always at the same grid frequency and voltage, independently from the speed and the orientation of the prime mover, from which depends the amount of the generated power.
For this purpose, tradictional asynchronous generators are commonly used, connected to a power grid, mechanically driven by prime movers in iper-synchrounous operations, above which the induction motor becomes generator. This kind of applications on a side consents to generate electric energy at the same grid frequency and voltage also with prime 1 movers characterized by variable speed, on the other side its use is limited by the necessity to achieve high speed, near the synchronous one. Other power plants with prime movers, characterized by a highly variable speed, are equipped with syncronous generators, with variable frequency and speed, connected to the power grid by means of power converters (solid state or rotary) to make the frequency and the voltage consistent with the power grid requirements.
Also double fed generators have been adopted, with statoric and rotoric windings connected to the power grid system, with suitable converter for the excitation winding: this consents to produce electric energy suitable to be supplied to an electric power grid. Still now, the complexity of the conversion and regulation systems has limited the diffusion on a large scale of these last two systems, while in the first case the adoption of a traditional asynchronous generator doesn't consent the complete exploitation of those power sources which are strongly variable. The basic aim of the present invention is to avoid the disadvantages and the limitations described in the above systems, designing a three-phases generator which could be immediately connected to the grid, powered by a prime mover having a very variable speed- range and witth high flexibility, adaptability, easy to design and with high efficiency.
A second aim of the invention is to design an asyncronous generator that could be directly connected to the power grid so to supply the generated power at its own frequency and voltage. A third aim of the invention is to propose an asynchronous generator that could be powered by different types of prime movers, with different dimensions and that could be connected to a power grid without complex regulation and control devices. A fourth purpose of this invention is to design a generator connected to the power grid which could produce electric energy independently by the rotation direction of the prime mover.
These and other purposes, to be detailed below, are all satisfied by the proposed asynchronous generator, characterized from a
synchronous speed equal to zero and therefore it becomes a generator at any angular speed different from zero, which is 5 imposed by the main shaft driven by a variable speed prime mover.
Other advantages and characteristics of the present invention will be understandable after the follow description of two different o embodiments, represented in the enclosed drawings which are intended for an illustration purpose and not as limiting sense, whereby:
Fig.1 shows a first executive embodiment. The generator is obtained by joining rigidly the shafts of both the three-phases 5 asynchronous motors (a) and (b), with squirrel cage, with a bushing (c) forced on the motor shafts (f) and (g); the case of the motor (b) is free to rotate respect to the case (a), which is anchored to a basement (t); the terminals (d f ) of stator winding are connected to the power grid (r) by means of the collector with slip 0 rings (e) and the brushes (s); the terminals of statoric winding (d) of the machine (a) are also connected to the line (r). Consequently to the connection to the grid (r), the rotors of both the machines, which are mechanically joined, turn at the synchronous speed ω s respect to the base and the shaft (m) 5 mechanically joined to the case of motor (b) will be standing still, but free to turn.
When the shaft (m), driven by a prime mover, starts to rotate in inverted sense respect to his rotor sense, the relative speed of the
rotor respect to the stator will become higher of the synchronous so speed and the machine (b) will become generator.
The rotor will be dragged and will tend to slow down his speed respect to the case of (a); the machine (a) will take the function of brake motor. The rotor of the machine (a) will assume the angularspeed ω a , respect to his stator, lower than ω s : this
85 corresponds to a torque M a .
The rotor of machine (b) will assume respect to own stator, which is rotating by means of the shaft (m), the speed u>b greater than ω s that corresponds to the torque M b : of course, at steady state, M a = M b -M m . This last represents the value of the torque developed by
90 the prime mover.
It's clear that uib - ω a = ω m , this last being the speed of the prime mover. The power developed from generator Pgen=(Mb * (jJb) - (M a * u) a ) is equivalent to the power of prime mover P m = M m * ω m , minus the mechanical and electric losses.
95 The same result will be obtained in reverse rotation sense. In this case will be ω a greater than ω s and ω b smaller than ω s . Fig. 2 shows schematically a section of a second embodiment which realizes the invention in a compact single machine that is composed of a case with a core (a) and relative (a 1 ) statoric loo winding connected to a power grid by a terminal box (d) and a rotor core (b) with rotoric winding (b 1 ) similar to the statoric winding (a'); the rotor core is assembled to the driving shaft (m), supported in the case by means of revolving bearing (n); the rotor winding is connected to the power grid with a collector with slip
105 rings (e) and with the brushes (s).
The hollow element (c) is : arranged between the stator and rotor, separated by two air-gaps (u 1 ) and (u"), free to turn on the revolving bearing (o) around the shaft (m).
This element (c) is realized. with the well-known technique of the 110 squirrell cage rotor, and it is composed by a cylindrical hollow core realized with a stack of iron laminations like in Fig.3.
The core is designed with slots arranged longitudinally on the ' outside and inside surfaces, with conductor bars set into grooves • and connected together at both ends by shorting rings forming two us cage-like shape, so to realize two short circuits windings that interact respectively with the stator (a) and with the rotor (b).
When the machine is connected to the power grid, the, rotor (c) is freely rotating at the synchronous speed. If the shaft (m), mechanically linked to the prime mover, is rotating, the machine 120 behaviour is like that described before, about the first embodiment of the invention.
Several modifications and variations could be applied to the . design of the invention: furthermore, all the details can be replaced by others technically equivalent.