Electrical Practice in Collieries: A Manual for Colliery Managers, Under ... by Daniel Burns

Author:Daniel Burns
Language: eng
Format: epub
Publisher: C. Griffin & company, limited
Published: 1903-03-25T05:00:00+00:00

situation that the person in charge can see his train when it comes to the landing place.

In this system a single road is all that is necessary unless a very large output is contemplated, in which case the road may be double. If a single road be used, one drum only is necessary, if a double road, two drums. These drums must be fitted with clutches and brakes,, so that they can be thrown out of gear when necessary. The maximum speed with a well laid road may be taken as 10 miles an hour. The average speed, however, will be less than this, depending upon length of run, power of motor, and general facilities for getting up speed.

Where the situation of the motor is dry it may be arranged to drive the drum by belt, and when this is done the motor must be fitted with a sliding bed plate and tightening screws to permit of easy adjustment of the tension of the belt. An extension of the bed plate to allow a third bearing to be fitted outside the driving pulley, so that the pulley runs between two bearings, is an important feature, especially where the work is heavy. The motor must be fitted with resistance coils so that the speed of running can be regulated. Where the mine i& a fiery one all parts must be enclosed in gas-tight cases so as to prevent accident should 8])arking take place. Should the situation be unfavourable to belt driving, gearing may be employed. This would render the plant more compact and reduce the cost of excavation of the site, but would increase the cost of the plant itself.

The general method of arrangement of such a plant is shown in Fig. 89.

In this case where the drum can be thrown out of gear by the clutch, the motor only requires to run in the one direction, and need not be provided with a reversing switch. Fig. 89a shows a geared plant for the same purpose.

Where the grade is uniform the motor may be series wound, as this form of winding gives the greatest starting power, and runs well where the load is not subject to variation.

The voltage will be determined by the distance from the generator, coupled with the conditions the generator may have to fulfil in supplying current to other plants, situated in other parts of the mine. The voltage may be from 210 to 420 volts,* according to distance, the higher voltage being used the further the power has to be transmitted. The motor room could be lighted from the mains; with the lower voltage one lamp in parallel would be used, with the higher voltage two lamps in

* The use of currents at from 400 to 600 volts pressure is now generally adopted about colUeries.

ELECTRICAL PRACTICE IN COLLIERIES.

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