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ALTERNATING MOTORS FOR RAILWAY WORK. 181 
and were coupled up to a special controller, designed to 
vary both the armature resistances and the field connections. 
These connections were threefold, the mesh or /\ for ex- 
treme torque, star or Y for normal full speed running, and 
‘‘ concatenated ’’ for half speeds. 'The latter was a quasi- 
series connection giving much the same result as reducing 
the primary voltage, without calling for special appliances. 
(8] 
PER HGQU 
DS BRAWBAR|PULL 
2900 
  
3000 4000 
FIG. 99. 
The curves for the most part explain themselves. 
The A curves refer to current, the B curves to efficiency, 
and the C curves to speed of car. Although the concat- 
enated connection was decidedly inferior in efficiency, 
both real and apparent, to the others, it still gave half speed 
very smoothly and with an efficiency reasonably high. 
The drawbar pulls registered were amply great for any 
service conditions, and the net commercial efficiency given, 
which includes all the gearing losses, compares not unfa- 
vorably with ordinary continuous currents. The running