### DC Generators Objectives Part 03

**41 . ** The number of mechanical and electrical degrees for a dc generator will be the same when the generator has** 2 poles.**

**42 . ** A dc generator running at 1600 rpm gives 240 V dc. If the speed is dropped to 1400 rpm without change in flux. The new emf will be **210V.**

**43 . ** In dc generators, an interpole field coils are connected **in series with armature.**

**44 . ** In a dc generator the polarity of interpol**e is same as the polarity of the main pole that precedes in the direction of rotation. (In motor, reverse)**

**45 . ** When a dc generator is operating at constant speed, variable load,** copper loss is likely to vary significantly.**

**46 . ** Total losses in a properly designed 1kW dc generator may be of the order **50W.**

**47 . ** If the no load voltage of a certain generator is 220V and the rated load voltage is 200V, then the voltage regulation is **10%.**

**48 . ** In a duplex winding for a 4-pole machine, the number of parallel paths will be **8.**

**49 .** In dc generator **External characteristics = magnetization characteristics-armature reaction-Ohmic drop.**

**50 . ** Series generator cannot start if there is no residual magnetism.

**51 .** The direction of rotation of a shunt generator can be reversed by **interchanging the polarity of field winding.**

**52 . ** A shunt generator running in 600 rpm has an induced emf of 200 volts. If the speed increases to 750 rpm, the induced emf will be **250V.**

**53 . ** A sinusoidal voltage of frequency 1 Hz is applied to the field of a dc generator. The armature voltage will be **1 Hz sinusoidal.**

**54 . ** Equalizer rings in lap wound dc generators are used to avoid **unequal distribution of current at the brushes thereby helping to get sparkles commutation.**

**55 .** Hysteresis loss in a dc shunt generator varies as** 1.6 power flux density.**

**56 . ** The critical resistance of the dc generator refers to the **resistance of field.**

**57 .** In a dc generator if field winding attains the critical resistances the voltage generated will be **zero.**

**58 . ** In a 4-pole dc machine alternate poles are** north and south.**

**59 . ** If A be the commercial efficiency, B be the electrical efficiency and C be the mechanical efficiency of a dc generator then **A=BxC** relation is valid.

**60 . ** Overall efficiency of a well-designed generator may be expected to be around **90 to 95%.**