Patent GB-576654-A (GB)
Title: Improvements in plant for testing prime movers
IPC: G01L3/22
Filed: 1942-07-07
Abstract: 576,654. Electric dynamometers. HEENAN & FROUDE, Ltd., ROSS, E. G., and WALKER, G. H. July 7,1942, No. 9392. [Class 106 (ii)] Relates to the type in which the stator rocks and is fitted with torque-reaction weighing apparatus the electric power developed being transmitted to a supply network, and comprises the combination of a synchronous generator with an asynchronous generator together with one or more slipping clutches, the synchronous generator being provided with a squirrel cage winding so proportioned that the pull-out torque of the generator will be of the same order of value as the natural pull-out torque of the asynchronous generator. The engine 1 Fig. 1, has two coaxial output shafts 2, 6. The inner shaft 2 is connected by coupling 3 to one end of a through shaft 4, the other end of which carries the outer member 5 of an eddy current clutch. The outer shaft 6 carries the outer member 7 of a second eddy-current clutch the inner member of which is carried by a hollow shaft 9 which carries the rotor of an asynchronous machine having a stator 11. The inner member 12 of the first clutch is carried by the shaft 13 of the synchronous machine. The rotating field 14 operates within the stator 16. The shaft 13 is continued to carry the armature and commutator 15 of an overhung exciter, the field system of which is carried by arms 18. The torque weighing gear for stators 11 and 16 may be as described in Specification 548,128. A transformer 24 Fig. 2, connects the A.C. system of the dynamometer to the mains (one phase only being shown), the said system being connected to the transformer through a resistor 25 and contactor 27, a shorting contactor 26 being provided. To start up the high-tension supply is closed and contactor 27 next closed. Current is thus placed on stator windings 11, 16 at reduced voltage due to impedance 25. The two A.C. machines come up to speed independently of the prime mover 1. The switch 28 being open, being connected to contactor 27, the exciter 15 cannot excite coils 8, 12. After a time contactor 26 is closed, by hand or time relay, and full line voltage placed on windings 11, 16. During time of coming up to speed, exciter 15 builds up its voltage and machine 14, 16 pulls machine 10, 11 into step automatically. The contact 29 is now closed and coils 8, 12 are excited. The slip of the clutches is adjusted by regulating resistance 30, 31 so that members 7, 5 rotate at speeds desired to drive the shaft 6 and 2 of the prime mover. The speeds of these are brought up to somewhat less than the speed of the synchronous machine. At this point the throttle of the prime-mover 1 is opened and the prime-mover allowed to develop power. By adjusting the regulators 30, 31 and the engine throttle the engine comes to its own full speed, and while the synchronous machine 14, 16 remains at synchronous speed to the A.C. line, the machine 10, 11 will slip. Both machines now supply power to the high tension system, but the excitation for machine 10, 11 is drawn from the stator 16 of machine 14, 16. The regulators 30, 31 may be replaced by excitation means as in Specification 524,080. Specifications 519,159 and 538,820 also are referred to.