that's not ward lconard that's "WARDD LEONARD". Ward leonard
system is nothing but the combined system of Motor and
generator coupling through the MECHANICAL motive. it's very
useful metod for SPEED CONTROL PURPOE. And it's mostly USED
in RAILWAY TRACTION system.

system, a prime mover drives a direct current (DC) generator
at a constant speed. The armature of the DC generator is
connected directly to the armature of a DC motor. The DC
motor drives the load equipment at an adjustable speed. The
motor speed is adjusted by adjusting the output voltage of
the generator using a rheostat to adjust the excitation
current in the field winding. The motor field current is
usually not adjusted, but the motor field is sometimes
reduced to increase the speed above the base speed. The
prime mover is usually an alternating current (AC) motor,
but a DC motor or an engine might be used instead. To
provide the DC field excitation power supply, Ward Leonard
systems usually include an exciter generator that is driven
by the prime mover.[3][

This is unidirectional speed control of dc shunt motor by 
varrying the field flux.

ward leonard control is a very efficient way of speed 
control in motors.in this method  we vary the stator 
voltage to control the speed.
most important feature of this method of speed control 
is ,we can increase & decrease the speed with respect to 
the base speed.