Circuit Details; Emergency Starting - Triumph SPEED TWIN 1945 Workshop Instruction Manual

LUCAS RM 14 A.C.
LIGHTING A N D I G N I T I O N
GENERAL DESCRIPTION
Under N O R M A L running conditions, electrical energy i n the form of rectified
A.C.
passes through the battery from t h e alternator-the rate of charge depending o n
the position o f the lighting switch. W h e n no lights are i n use, the alternator o u t p u t
i s sufficient only t o supply the i g n i t ~ o n coil and t o trickle-charge the battery. W h e n
t h e lighting switch is turned t o the "PILOT" o r "HEAD" positions, t h e o u t p u t
increases proportionately.
Under EMERGENCY starting conditions, trickle-charging continues whilst
ap
ignition performance similar t o that from a magneto i s obtained. AFTER T H E
ENGINE HAS'
BEEN
STARTED, NORMAL RUNNING IS .RESUMED BY TURNING
THE IGNITI0.N KEY FROM "EMG" t o "IGN". IF THE BATTERY MUST BE
REMOZED. THE ENGINE C A N BE R U N W I T H THE I G N I T I O N S W I T C H
IN
T H E
"EMG" POSITION PROVIDING T H A T THE BATTERY NEGATIVE CABLE ( B R O W N )
IS
EARTHED T O THE FRAME. UNDER THESE CONDITIONS N O LIGHTS ARE
AVAILABLE.
CIRCUIT DETAILS
The alternator stator carries three pairs of series-connected coils, one pair being
permanently connected across the rectifier bridge network. The purpose o f this
latter pair is t o provide some degree of charging current for the battery whenever
the engine i s running.
.Connections t o the remaining coils vary according t o the positions of t h e lighting
and ignition switch controls.
W h e n no lights are i n use, the alternator o u t p u t
from the battery charging coils is regulated t o a minimum by interaction of t h e r o t o r
flux set up by current flowing i n the short circuited toils.
In the "PILOT" positions these latter coils are disconnected and the regulating fluxes
are consequently reduced. The alternator o u t p u t therefore increases and com-
pensates for the additional parking light load. In the "HEAD" position, the alternator
output
i s
further increased by the connection of all three pairs of coils i n parallel.
EMERGENCY STARTING ( I G N I T I O N SWITCH A T EMG.)
W i t h this circuit the contact breaker i s arranged t o open when the alternating
current i n the windings reaches a maximum. The ignition coil primary winding
and the contact breaker are connected i n series. W h e n the contacts separate H.T.
current i s induced in the coil secondary windings, thus producing a spark at the plug.