The torque angle of a synchronous machine operating from a constant voltage bus, is usually defined as the space angle between

The developed electromagnetic force and or torque in electro $$-$mechanical energy conversion systems act in a direction that tends

Figure depicts the load characteristics of an constant speed. Match the following sets of operating conditions with the given characteristics. Disregard the effects of saliency, saturation and stator resistance.

$$(a)$$ Constant excitation and non-zero leading power-factor
$$(b)$$ Constant excitation and zero power-factor, leading
$$(c)$$ Constant terminal voltage and zero power-factor, leading
$$(d)$$ Constant terminal voltage and non-zero leading power-factor

Neglecting all losses, the developed torque $$(T)$$ of $$d.c.$$ separately excited motor, operating under constant terminal voltage, is related to its output power $$(P)$$ as under