Home > Electricals Menu > Vickers-Hall Lighting System Description

Vickers-Hall Lighting System Description

The following is an extract of a booklet published in 1905 titled "Train Lighting", "The Vickers-Hall System" from Vickers, Sons & Maxim Ltd., 32 Victoria Street, London. Are any examples of this system still in used on preserved lines?

The Vickers-Hall Train Lighting System.
In this system, as in all others where the power is taken from the car-axle, the primary apparatus used consists of a dynamo with either one or two sets of accumulators. When the train is standing, current is supplied by the accumulators; and when running, either partially or wholly by the dynamo. The remainder of the apparatus consists of various arrangements for regulating the current from these two sources and switching them into, or out of action as required.
There are two systems of lighting included under the general name of "Vickers-Hall." namely, the Single Battery System, in which only one set of accumulators is employed, and the Double Battery System, in which two sets of cells are used. Two voltages are employed, 30 or 24 according to requirements, but the former is only used with large coaches requiring a No. 2 equipment. 15 cells per battery are used with the 30 volt system, and 12 with the 24 volt system,. The Double Battery System is generally used on large dining and sleeping cars, where the great storage capacity required would make the cells too large to be handled by one man were it not split up among a large number of cells. The advantage of this when fitting up a coach, or when removing the cells for their periodical inspection and washing out, etc., is obvious.
The Double Battery System also offers certain advantages with regard to the employment of separately controlled lamps, it being possible to fit a much greater number of these than in the case where the Single Battery System, is fitted. The Single Battery System is mainly employed on small coaches using about 20 lights, arranged on "half" and "full" light circuits, with not more than one or two separately controlled lamps in each circuit. If more separately controlled lamps are required, a special compensating arrangement is attached to each switch.

THE SINGLE BATTERY SYSTEM.

single battery configuration

GENERAL REMARKS.

In this system, as its name implies, only one set of accumulators is employed. The dynamo is adjusted by means of the output adjuster described later, to generate a current greater than that required for the lamps, the amount of excess current depending upon the conditions of the service on which the equipment is to be used. This excess current passes into the accumulators, and is there stored to supply the lamps at times when the dynamo is disconnected (when its voltage is below that of the cells), by means of the automatic cut-out switch, which also connects it up again when its voltage is above that of the cells.
In order to protect the system against sudden rushes of current due to accidental short-circuits, fuses are fitted, one in each lamp circuit, one in the main dynamo circuit, and one in the dynamo shunt. Should it happen that the coach is employed for any length of time on a service where no lights are required, the shunt fuse should be removed, thus preventing the dynamo from generating and overcharging the cells. It should, however, be replaced for a short run occasionally in order to keep the cells in good condition.

THE DYNAMO.

This is a 4-pole compound wound machine with drum armature. The series coils of the field are wound inversely in such a manner that when in circuit they weaken the field. In addition to the ordinary parts of a dynamo the casing contains the pole changing and regulating mechanism described below. Self-oiling bearings are used, with oil wells containing sufficient oil to last for about three months. Carbon brushes are employed for the sake of obtaining good commutation.

THE REGULATING MECHANISM.

The regulating mechanism is comprised of the following parts :
1. The Governor. This consists of a round body (4) containing two radial slots placed diametrically opposite each other. In these are placed two weights designed to slide with the least possible friction. These weights (5) are connected by means of chains (12) passing over rollers (6) to an arrangement called the spring box (8), which slides on the shaft and is pressed away from the governor body by springs (7). The spring box is attached to a tube which slides with it, and forms the cone of a ball bearing (9). The cups of the ball race are fixed in an aluminium cup (13), having two arms which carry the brushes (16) of the Lamp and Regulating Slides (see below). This cup thus slides axially with the spring box, but does not turn with the shaft. All governors are made to gauge and carefully tested before leaving the works so as to be perfectly interchangeable; thus any governor may be put into any machine without in any way affecting the regulation.

THE REGULATING SLIDE (Ref. 14)

This is an arrangement consisting of a number of contacts and a sliding short-circuiting brush moved by the governor, and so designed that when the dynamo is at rest both the inverse compound coils and the regulating shunt resistances are short-circuited. As the machine increases its speed while running, first the compound coils are thrown into circuit, and when they are all in, the shunt resistance is cut in step by step. By this means the output of the dynamo is kept constant over the entire range of speeds.

THE LAMP RESISTANCE (Ref. 15).

This is a resistance in the lamp circuit so connected tO the main switch that when the lamps are being supplied from the dynamo, if half lights are on, the lamp current passes through the whole of the resistance, but if full lights are on, only through part of it. The method of effecting this can easily be seen by referring to the diagram (Fig. II),the middle terminal of the resistance being connected to the "full light" terminal F1 of the switch, and the end terminal of the resistance to the "half light" terminal H1 of the switch. The Resistance is composed of units built up on a slide similar to the Regulating Slide, so that when the dynamo is at rest and the lamp current is being taken from the cells, the whole of the resistance is short-circuited, but as the dynamo increases its speed, the resistance is cut in step by step until when the dynamo reaches its full output the whole of the resistance is in circuit. This resistance prevents the rise of voltage which would otherwise occur at the lamp terminals when switching from half to full lights. {See Diagram of Connections, Single Hattery System, Fig. II.)

THE POLE CHANGER ACTUATOR (Ref. 17).

This consists, of a body (17) containing two radial guides revolving with the shaft. In the guides slide two weights or hammers (18), which, when the machine is at rest, are held at the inner ends of the guides by springs. When the dynamo first starts they strike the trigger (21) of the pole changing switch, thus ensuring that the switch is in the proper position, but as soon as the shaft has reached an appreciable speed the weights fly out at the end of the slots and so clear the trigger, thus avoiding unnecessary wear of the surfaces which come into contact.

THE POLE CHANGING SWITCH (Ref. 19).

This is a switch consisting of two insulated moving blades and three fixed contacts, the two outer of which are connected together, the whole forming a reversing switch. The blades are connected to the dynamo brushes, while the contacts are used as terminals of the exterior circuit. The switch is forced over one way or the other, according to the direction of rotation of the armature by the action of the pole change actuator as described above. The two outer terminals are thus always positive and the centre one negative, and no part of the system outside the pole changer terminals is affected by the direction in which the train is moving.

THE OUTPUT ADJUSTER.

This is fitted in a box fixed on the side of the dynamo, and in some cases inside the coach, and consists simply of a variable resistance interposed in the shunt circuit of the dynamo. By means of this the output of the dynamo can be set at any desired amount between about 15 amps and 30 amps in the case of a No. 1 machine, and 25 amps and 50 amps in the case of a No. 2 machine. (See diagram, Fig. II.)

THE CUT-OUT.

This is placed in some convenient position inside the coach, and consists of an automatic switch actuated by a solenoid. This solenoid is compound wound, one winding of fine wire being connected across the dynamo terminals, the other, of large wire, carrying the main current. These windings are so arranged that when the main current is in the correct direction, it reinforces the effect of the shunt current, but if in the wrong direction, opposes it. A controlling spring is provided of such strength that when the voltage of the dynamo reaches six volts above the nominal voltage of the system (i.e., 30 volts in a. 24 volt equipment, and 36 in a 30 volt equipment) the pull of the shunt windings closes the switch against the tension, of the spring, thus allowing the dynamo current to pass to the lamps or batteries. The main current now reinforces the shunt and insures a firm contact. When the dynamo slows down, as soon as its voltage falls below that of the cells, a current flows in the reverse direction through the series coils, so opposing the due pull to the shunt current, when the cutout is opened by its own weight, aided by the tension of the controlling spring. (See diagram. Fig. II.)
The cut-out box also contains the main and shunt fuses and an arrangement by means of which an ammeter may he inserted in the dynamo circuit.

THE MAIN SWITCH.

There are two forms of main switch, one of which is fixed outside, the coach, and worked by means of a cross-bar, extending across the coach, with a handle at each end, the other fitted inside the coach. Either form consists of four contacts so arranged that when the switch, is at "half lights" only two of them are connected together, and when the switch is in "full lights" all four are connected, thus short-circuiting the portion of the lamp resistance which is joined to the two contacts, H1 and F1, of the switch. (See diagram, Fig. II.)

WORKING OF THE SYSTEM.

The action of the single battery system, is as follows : When the dynamo is at rest or moving too slowly to generate a voltage above that of the cells, the cut-out remains open, thus completely disconnecting the dynamo from the rest of the system. The Lamp Resistances in the Lamp Slide are all short-circuited, and any lighting current required is supplied by the cells, which are now connected directly in series with the lamp circuit. When the dynamo is generating a voltage above that of the cells, the cut-out closes as previously described, and the current required for the lamps- is taken from the dynamo through the cut-out, and all or part of the lamp resistance, according to the speed of the dynamo and the number of lamps in circuit. The surplus current from the dynamo passes into the cells.
In order to ensure the machine picking up, a few laminations of permanent magnet steel are inserted in the fields, and the shunt circuit being always closed, the field rapidly builds up when the train starts. It is thus unnecessary to provide any means for exciting the field off the cells at starting.

THE DOUBLE BATTERY SYSTEM.

double battery configuration

GENERAL REMARKS.

In this system two batteries of accumulators are employed, and the action is briefly as follows : When the dynamo is not generating, the two batteries supply the lamps (if in, use) in parallel. When the dynamo is generating, the current from it passes partly into one battery, and partly through a variable resistance on the "lamp slide" to the lamps, supposing them to be on. The second battery "floats" on the lamp mains and so regulates the voltage at the lamp terminals. If the lamps are not in use the "lamp slide" is short-circuited, and the two batteries are charged in parallel. (See Fig. III.) THE DYNAMO AND REGULATION.

The Dynamo and Regulating Mechanism, also the output adjuster, are exactly the same, except that the lamp slide has no middle terminal.

THE CONTROLLER BOX.

This, like the Single Battery Cut-out which it replaces, is fitted inside the coach, and contains the main and shunt fuses, two automatic switches or cut-outs, one for each battery, the change-over switch, and an arrangement for inserting an ammeter into the main circuit when required.

THE CUT-OUTS OR AUTOMATIC SWITCHES.

These are exactly similar to the cut-out used in the Single Battery system, except that each is fitted with an extra pair of contacts and a brush which connects them when the cut-out is in the "down" position. There are thus eight contacts, which are arranged in two rows. The outside left contacts in each row are connected together and to the positive lead from one battery, the outside right contacts being similarly connected to the other battery. The inside contacts in the top row are connected each through the series windings of its own solenoid, to the positive terminal of the dynamo, and the inside contacts in the lower row are connected together and to the lamp switch. By this means each cut-out connects its corresponding battery, when up to the dynamo, and when down, to the lamp switch.

THE CHANGE OVER SWITCH.

This is of barrel form with spring contact fingers, and is placed at the top of the controller box. The object is to ensure the alternate working of the solenoids, so that the functions of the batteries are interchanged after every stop. It is connected in the shunt circuit so as to excite the shunt windings of each cut-out alternately, and is actuated by means of two ratchet wheels mounted on its axle, with the teeth of which two pawls fixed on the plungers of the cut-out solenoids, engage, so that the switch is moved one step forward each time the train stops. Owing to this action of the change-over switch, the cut-outs cannot both close at the same time. They are, however, both open when the dynamo is not generating, so that in that case the batteries are thrown into parallel. The above will be easily understood if read in conjunction with the diagram of connections of the Double Battery System. (Fig. III.}

THE MAIN SWITCH.

This consists of an ordinary two-way pole switch with fuse on each way, the brush being wide enough to cover the contacts of both ways, so that either or both of the sets of lamps are used. There are also two extra contacts, which are so placed as to be bridged by the brush when in the "off" position. These are connected to the positive leads from each battery so as to short-circuit the lamp resistance when no lights are in use.

THE LAMP RESISTANCE XI X2 (See Fig. III).

This is a resistance arranged on a slide as in the Single Battery System, but only having two terminals, one at each end. It is connected between the positive terminals of the batteries, so as to be directly in circuit between the dynamo and the lamps. It is proportioned so that when the dynamo is generating its full output, and the whole resistance is in circuit, the correct proportion of the dynamo current required for the lamps, passes through it; at lower speeds, when the dynamo output is less, a portion of the resistance is short-circuited by the regulating mechanism, so that the proportion of current passing to the lamps is greater. Just before cutting out, the whole of the lamp resistance is short-circuited, thus throwing the two batteries into parallel.

CONDITIONS OF WORKING.

There are four conditions of working:

(1) Dynamo not Generating, Lamp Switch Open In this case each battery is connected through the lower contacts and brush of its corresponding cut-out to the lamp switch, but this being open no current passes. The batteries are, therefore, short-circuited upon one another, so that if one battery be at a higher potential than the other, current will flow between them until they are balanced.

(2) Dynamo not Generating, Lamp Switch Closed As in case No. 1,both batteries are connected to the lamp switch, The lamp current is thus divided between the two batteries, that which is at the higher potential of course supplying most current, and so again tending to balance the batteries.

(3) Dynamo Generating, Lamp Switch Closed. In this case, one of the cut-outs will be closed and the other open, their positions being reversed after every stop by the action of the change-over switch. The current from the dynamo passes through the series coils and upper contacts of the closed cut-out to the corresponding terminal of the controller box, and thence to the terminal of the corresponding battery. Here it divides, one part passing through the variable resistance on the lamp slide to the lamp switch and lamps, the other charging the battery. The second battery regulates the lamp voltage, receiving or giving out current according as the amount of current passing thiough the lamp resistance is greater or less than that required by the lamps.

(4) Dynamo Generating, Lamp Switch Open. The lamp resistance is short-circuited. The dynamo current divides itself between the two batteries, so that each receives a due proportion of the charge.

METHOD OF FIXING THE APPARATUS-
1. The Dynamo is provided with four lugs on top, through which pass two steel shafts parallel to the axis of the machine. To these are connected four wrought iron links, which are suspended from two other steel shafts rigidly fixed to the carriage by means of four wrought iron hangers. The links are all equal in length, so that the dynamo is constrained to swing horizontally, thus avoiding any trouble which might arise with the ring lubrication if the machine were allowed to tilt. A tension spring with adjusting link is provided to keep the tension on the belt while allowing the dynamo to give freely to the motion of the bogie.

The Cells are arranged in groups in boxes under the coach. The bottoms of the boxes have two iron straps running along them, and projecting at the ends, through holes in which pass at each end two long bolts or hangers secured to the under-frame. Nuts are placed on the screwed ends of these below the straps, by means of which the box is securely clamped up either against the original frame of the coach, or special trimmers inserted for the purpose. Should the box be very long, a cross bar should be fixed across the middle, and supported by two more hangers similar to those at the ends.

The Controller Box with the Double Battery System or the cut-out with the Single Battery System should be placed in some convenient position inside the coach.

The Main Switch, if of the exterior type, is placed at the end of the coach with the cross-bar extending right across, so that it can be worked from either side. In coaches where an interior switch is fitted, it is placed in any position where access to it can be readily obtained.

For a description of the system dynamo, click here.