Synchronous generator and synchronous
motor are physically the same machines!
A synchronous machine can supply real
power to (generator) or consume real
power (motor) from a power system. It
can also either consume or supply
reactive power to the system.
1. The distinguishing characteristic of a
synchronous generator (supplying P)
is that EA lies ahead of Vφ while for a
motor EA lies behind Vφ.
2. The distinguishing characteristic of a
machine supplying reactive power Q
is that Eacosδ > Vφ (regardless
whether it is a motor or generator).
The machine consuming reactive
power Q has Eacosδ < Vφ .