Dnepr MT10-36 - Page 71

centre dis tance of the drive gearing), an d a flange for securing the
ge nera tor on the mCPton cyde eng ine cr . ankcase .
The gener at or is pr ovided at the drive end with rubber gland 2
to isolat -e the in ner space of 1Jhe generator from t he aggressive me-
dium of the 'C rankc ase . Ro tat ing in sealed - fo r-life bearings 11 , pa -
cked on both sides, is rotor 3 with a field winding and slip rings.
Three-pha t se w inding 4 of the stator is star~con ne cted w ith an
insu l ate d ne utral wire . The p has e leads are soldere d to the heads of
bolts securing rectifier un it 8. T wo covers, 1 and 6, as well as s tator
ane f·i tted toge th er by mea ns •of three · screws M6. Th e brus h es with
cur re nt-carrying plates are sec ured t-o brush hold er 7 an d cover 6
wit h the help of screws whic h are !preven ted from falli ng- out.
Th e gen erator incorporates se m iconductor rectifie r unit 8 type
B5f- ·2A which permi ts a di rect c urr ent to be obt ained from the ge-
nerator termina ls.
The rect i·fier unit consists of th re e monoblocks which are cast
from aluminium all oy and provided with fins ,for h eat dissi·p ation.
Eac h of the m onobloc ks is fitted wit h two se mico ndu cto r elemenfs
of opposit e ,p olarity, the electr i ca l co nn ection between them is ensu -
red by two t busbar s (one of which is in sulated and the other con-
ne cte d to "ear th"). The insula 1te d busbar is provi d ed with a -clam-
p ing screw.
The re ctifier un it mu st neve r be di sassembled .
Moun ted on the extension of roto r 3 shaft, under protective ca-
sing 10, is axia l fa n 9, which is intend ed to cool the rectifier unit.
The terminals for conn ectio n of the ge n erator to the electric circuit
of the motorcy cle are avai!table on common te rmin al block 5 and are
fitted with l imioti ng was hers to avoid the possibility of ·confusing the
co ndu ct ors during wiring and to · prevent occasiona l disconnection of
the conductors in opera tion .
0 perating Principle
The ope r ating principle of the f424 generator is si milar to that
of any other three-phase sy nchronous machi ne wi·th e l" ectr omag netic
excitation, but this generator h as the fo llowing distinguishing fea-
tu res:
when start intg from res t an d during speeding-up, flhe field win-
ding of the generator must t be ener . gize d from an extern a 1 d. c. so-
<J rce (a storage battery), and the genenator starts to operate as the
res ult of self-exci tation only a ft er being exdted f·r om the sto r age bat-
tery at i.he rotor speed exceeding 2400 r. p. m .
Operating the generator with the storage battery completely dis-
charged is impossible since the g enera t or fails to be excited .
In case the g enera ' tor i•s 01 p erated without load ( the wires lead -
ing to the con sllil11ers bei ng rup t ur ed or disconnected) at a high
spee d, the a. c. voltage b etwee n the phases reaches a va lue that may
cause the semico ndu ctor eleme nt s of the unit to be punctured and the
generator to be d amaged.
6 ()