A shunt DC machine is shown below. You are given the following parameters: Armat

Question

A shunt DC machine is shown below. You are given the following parameters: Armature resistance, R_a = 0.5 ohm Armature inductance, L_a = 1 mH Field Inductance, L_f = 10 mH Applied Voltage, V_a = 250 V Field Resistance, R_f = 100 ohm Rotational Speed omega_m = 1500 rpm It is known that the armature current is I_a = 10 A. Calculate the input power (P_in), the developed power (P_dev), in Watts, and the back emf constant (K_c). Now suppose that V_a = 200 V and omega_m = 1500 rpm. Calculate the electrical losses (P_loss-else), the output power (P_out), and the overall efficiency (in %) of the machine if the mechanical losses are 1,000 W.

Explanation / Answer

a)

1. Pin= Vs * Ia = 2500W

2. power devloped= Eb * Ia

Eb= Vs-Ia *ra= 250-5 =245V

EB = Ke* wm hence ke= 245/1500

now Va=200

Plosses = If^2 * Rf + Ia^2* Ra

poutput= Eb * ia

Ebnew= 200-10*0.5=195V

Eff= Pout/(pout+losses)

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