9-B] INDUCTION GENERATOR. 297 



must be a flow of wattless magnetizing current* to set up the 

 flux ; otherwise the generator can produce no voltage. 



This means that an induction generator will give voltage only 

 when it is connected to a circuit that allows the proper wattless 

 current to flow ; it can not operate when connected to a resistance 

 load (or other load taking power current only) unless there is 

 connected in parallel some device, as a condenser or synchronous 

 machine, that takes leading current. 



5. The size and cost of condensersf being prohibitive, the 

 induction generator in practice is used (a) in parallel with a 

 synchronous generator, or (b) in parallel with an over-excited 

 synchronous motor or converter. 



6. When an induction generator is used in parallel with a 

 condenser, synchronous motor or converter, the wattless current 

 is a leading current supplied by the generator to the condenser or 

 synchronous machine. Commonly but less logically, however, 

 this wattless current is described as a lagging current supplied to 

 the generator by the condenser or synchronous machine. The 

 synchronous machine is said to "supply the excitation" for the 

 generator. 



When the synchronous machine is a generator, there are two 

 generators in parallel and the current which circulates between 

 them is due to the combination of their two electromotive forces, 

 the current being lagging with respect to one and leading with 

 respect to the other. 



7. Uses. The induction generator has been but little used, 

 due no doubt to its inability to supply lagging current and the 



* (4a). Aside from saturation, the voltage of an induction generator at 

 no load is proportional to the wattless magnetizing current. As the load 

 increases, the wattless current is increased from BA to C'P G on account 

 of leakage reactance, as in a transformer or induction motor. The diam- 

 eter of the circle, E-+-X, becomes greater as X diminishes and would be 

 infinite when X = o. 



f For operation with condensers, see McAllister's "Alternating Current 

 Motors." 



