Two DC series motors connected in series draw current I from supply and run at speed N. When the same two motors are connected in parallel taking current I from the supply, the speed of each motor will be
Right Answer is:
In case of series.
When motors are connected in series and are in running position, Speed ∝ (voltage) ∝(V/2)
(i) (Since the voltage across each motor = V/2 ) and current is Ia.
Ns ∝ V/2I
In case of parallel
When the motor is connected in parallel and are in running position, Speed ∝ (voltage) (V). (Since the voltage across each motor = V ) and current is Ia/2
Np ∝ 2V/I
From both the equation
Ns/Np = V/2I/2V/I
N parallel = 4Nsereis
Hence it can be concluded that for the for low-speed operation motor may be connected in series and for high-speed operation motor is connected in parallel.