-
A 15kW, 230 V dc shunt motor has armature ci r cuit r esi st ance of 0.4 Ω and field cir cuit resistance of 230 Ω. At no load and rated voltage, the motor runs at 1400 rpm and the line current drawn by the motor is 5 A. At full load, the motor draws a line current of 70A. Neglect armature reaction. The full load speed of the motor in rpm is ________.
-
- 540
- 120
- 1240
- 140
Correct Option: C
Given 15kW, 230V dc shunt motor armature resistance Ra = 0.4 Ω
Field resistance, Rsh = 230 Ω
∴ Eb1 = 230 – 4 × 0.4 = 228.4 V
∴ Eb2 = 230 – 69 × 0.4 = 202.4 V
| ∴ | = | × | |||
| N1 | Eb1 | φ2 |
| = | (∵ Flux is constant) | |
| Eb1 |
| N2 = N1 × | ||
| Eb1 |
| = 1400 × | = 1240 rpm | |
| 228.4 |
