ELECTRIC TRACTION – PART – 09 - SPECIFIC ENERGY OUTPUT AND ENERGY CONSUMPTION & TWO PROBLEMS

PROBLEM -01

An electric train has an average speed of 42 km per hour on a level track between stops 1500 m apart. It is accelerated at 1.7 kmphps and braked at 3.3 kmphps. Draw the speed-time curve and estimate the specific energy consumption.

Assume tractive resistance as 50 N/ton and allow 10% for rotational inertia.

PROBLEM -02

A 400 ton electric train runs up an ascending gradient of 1% with the following curve.

1. Uniform acceleration of 1.6 km/hr./sec. for 25 sec.

2. Constant speed for 50 sec.

3. Coasting for 30 sec.

4. Braking at 2.56 km/hr./sec.

Calculate the specific energy consumption if train resistance is 50 N/ton, effect of rotational inertia 10%, overall efficiency of transmission gear and motor 75%.