A separately excited dc motor has an armature resistance Rₐ = 0.05 Ω. The field excitation is kept constant. At an armature voltage of 100 V, the motor produces a torque of 500 Nm at zero speed. Neglecting all mechanical losses, the no-load speed of the motor (in radian/s) for an armature voltage of 150 V is _____ (up to 2 decimal places).
Correct Answer
600-600
Solution & Step-by-step Explanation
Explanation:
At zero speed (N = 0)
induced voltage (E) = 0
∴ T = k ϕ Ia 1
⇒ T = kIa1 {∴ ϕ = Constant}
E = Vt - Ia1Ra
Ia1 = (100 - 0)/0.05 = 2000 A
Therefore,
K = (T/Ia1) = 500/2000 = 0.25
At no -load condition, load torque (TL) = 0
E2Ia2 = T ω
⇒ Iₐ₂ = 0
So, induced voltage
E₂ = k ϕ ω₂ = k ω₂ = 150
and k = 0.25
ω = E₂/k = 150/0.25 = 600 rad/sec
Therefore, no load speed of the motor is 600 rad/sec.
At zero speed (N = 0)
induced voltage (E) = 0
∴ T = k ϕ Ia 1
⇒ T = kIa1 {∴ ϕ = Constant}
E = Vt - Ia1Ra
Ia1 = (100 - 0)/0.05 = 2000 A
Therefore,
K = (T/Ia1) = 500/2000 = 0.25
At no -load condition, load torque (TL) = 0
E2Ia2 = T ω
⇒ Iₐ₂ = 0
So, induced voltage
E₂ = k ϕ ω₂ = k ω₂ = 150
and k = 0.25
ω = E₂/k = 150/0.25 = 600 rad/sec
Therefore, no load speed of the motor is 600 rad/sec.