Be warned! This is written in "patentese" and the grammer is appauling. It is also very
long. But if you want to know all the in's and out's of the MD and CMD regulator, read on!
To have any chance of understanding this, you need to print out the drawings (1606 x 1224 pixels).
Mechanical Drawing
Electrical Drawing
PATENT SPECIFICATION
349,148 Application-Date
: March 1, 1930. No, 6872/30.
Complete Accepted : May.28, 1931.
COMPLETE SPECIFICATION.
Improvements in and relating to Electric Supply Systems.
I, Herbert Foale, a British Subject, of 39, Western Road, Wolverton, in the County of Bucks, do hereby
declare the nature of this invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
This invention relates to electrical
systems comprising a variable speed dynamo working in conjunction with an accumulator or accumulators and more
particularly to train lighting installations in which the running conditions make it peculiarly difficult to
provide means cal-culated to meet satisfactorily all require-ments.
The general object of the invention is to effect certain improvements whereby not only is a closer lamp
voltage regulation obtainable but the constructional details are such as to simplify manufacture and provide
an assemblage of a very robust character reliable in use and requiring little supervision.
According to the present invention a regulator is employed which differs from similar known regulators chiefly
in that the control is mainly by variable voltage an essential feature being the combination with the exciting
circuit of the shunt coil of a regulator switch of the known type where resistance in the dynamo field circuit
is caused to gradually alter in the act of separating contacts, of a resistance and control switches therefor
so arranged that the shunt coil remains only slightly excited when the accumulator alone is in circuit or
until the lamp voltage reaches a predetermined value if the lamps are in circuit with an accumulator but
partially charged, at which time a section of resistance is shunted by a portion of the lamp circuit to
increase the excitation of the regulator shunt coil and reduce the excitation and consequently output of
the dynamo, to be followed by an equivalent short circuiting of a further section resistance when the lamp
voltage rises again to the predetermined value or to a value slightly in excess thereof.
With the above conditions of regula-tion, the temperature co-efficient of the regulator does not detrimentally
affect the charging of cells even in very low tem-peratures. At all times it charges the cells at a rate
suitable to their state of charge with or without the lamps being on circuit.
As has been proposed in
other systems it is advantageous to divide the series coil of the cut-in switch into two equal sections,
one section conducting the whole of the dynamo output current and the other section only conducting the
current to and from the accumulator (hereinafter referred to as the battery).
When the dynamo is
generating, the two coil sections assist each other and the usual associated shunt coil to operate the
cut-in switch . When lamps are on circuit and the speed of the dynamo is being reduced a time arrives
when the current to the lamps is being equally shared between the battery and the dynamo. Under these
conditions the magnetic effects of the two sections of the series coil are neutralised, and before any
reverse current is passed to the dynamo the cut-in switch opens. This results in an early cut-out when
the lamps are in use.
Another result of the halved series coil is that where only a few lamps are on circuit when the lights switch
is closed with the dynamo running and the battery well charged, the current for these lamps will be taken from
the battery as its voltage will be above the set regulator voltage for the lamps.
In these circumstances the discharge will take place through, one section of the series coil and cause the
cut-in to cut-out until the peak has gone off the battery voltage or more lamps are switched on. In both
cases the regulator immediately resets itself to the conditions prevailing at that moment, and the dynamo
will then supply any lamp current needed. Without the aid of one of the series coil sections the cut-in
switch will not operate satisfactorily on very small lamp loads when the cells are well charged as there
is then no current being carried by the other half of the series coil to assist the shunt coil.
The halving of the series coil therefore meets several conditions, viz. each half can assist the other, the
two can oppose each other, or each can act independently. The foregoing features and improved constructional
details will be more readily understood from the fuller description now about to be given with the aid of the
accompanying drawings whereof Fig 1 is a diagram, showing the circuit connections.
Fig 2 is a part sectional elevation and Fig. 3 a plan of the principal parts of the regulator. Fig. 4 is a
section taken on the line 4-4 of Fig. 2.
In the diagram, 1 represents the dynamo shunt field winding, 2 a resistance the function of which will be
subsequently explained, 3 and 7 lamp resistance switches, 4 a solenoid coil associated with switch 3, 5 a
sub-control switch, 6 a cut-in switch, 8 a dynamo series coil, 9 a battery series coil and 10 a shunt coil,
which coils 8, 9 and 10 are associated with the cut-in switch 6. 11 and 12 are lamp resistances, 13 a switch
operated by the regulator the contacts of which are designated 14. 15 is the field winding resistance, 16 a
stabiliser hereinafter described, l7 the regulator shunt coil, 18 the regulator series coil, 19 a coil
included in the shunt field circuit, 20 the battery, 21 a sectional resistance coil 22 and 23 voltage control
switches, 24 and 25 solenoids for the switches 22 and 23, 26 the light controller, 27 the "off"
solenoid and 28 the "on" solenoid therefor, 29 the lighting switch, 30 lamps, 3l positive main to
lamps. 32 and 33 are resistance coils.
35 is a so-called toggle coil. 36 is a full load coil, 36a a full load switch, 36b a full load adjuster or
resistance and 37a load limiting coil all of which in certain circumstances may be employed.
Before dealing further with the diagram it may be convenient to explain that the solenoid core for the
regulator switch indicated at 40 in Fig. 4 is in the form of a piston working in a brass tube 4l which
is soldered to a core part 42 screw threaded for connection in an adjustable manner to a supporting frame
43, this being an arrangement which ensures air tightness except by way of leakage past the piston 40,
thereby establishing a dash pot action, while also ensuring that the tube shall be effectually held against
accidental movement without having to be clamped and possibly injured by mechanical means. The same
construction may be adopted for all of the other solenoids employed except that air tightness is not
necessary.
Reverting now again to the diagram, it will facilitate explanation to assume a concrete example of a 25 volt
battery 20. The operation of the regulator is as follows:-
When the dynamo has reached a speed sufficient to generate 26v to 27 volts, the shunt coil 10 energises the
associated piston 44 sufficiently to close the cut-in switch 6 and sub control switch 5. Current then flows
through the series coil 8, switch 6 and the series coil 9. This strengthens the action of the cut-in solenoid
so that it still further raises the piston, and switch 7 which so far has been closed is then opened.
After passing the series coil 9 the current traverses the series coil 18 of the regulator (and the stabiliser
16 in parallel) to the positive battery terminal, and then through the battery to the negative terminal of the
dynamo.
Starting from a point 8a on the positive side of the dynamo there is a thin wire leading to
the resistance coil 21; after the current traverses this it goes direct to the shunt regulator coil 17 and
then to the negative battery terminal.
It is mainly due to the action of this shunt coil 17 that the regulator piston 40 Figs. 2 and 4 functions
and maintains its position according to requirements.
In the circuit just run through, the battery 20 is being charged when the lights are off, switch 29 being
open.
It is here to be noted that the whole of the resistance 21 is now in circuit with the shunt regulator coil
17 across the dynamo terminals. The dynamo voltage will be automatically adjusted under this condition, so
that it is a little above the battery voltage until the battery volt finally rises to about 32 volts when
the charging effect will be reduced to a very small value.
The effect of this method of regulation is that on commencing to charge a completely discharged battery a
large current flows through the stabiliser 16 and the wound so that it assists the shunt coil series coil
18, this series coil 18 being 17 to keep the charge to the battery within permissible limits.
The principal function of the stabiliser 16 is to check the tendency of the regulator piston 40 to shunt when
re-setting itself as occasion requires, the stabiliser as already stated being a low resistance permanently
coupled in parallel with the series coil 18. The relative resistance of the stabiliser 16 to the series coil
18 can be proportioned to determine the maximum amount of current allowed to pass to the battery. When the
battery voltage has risen owing to its being nearly charged, the current in the stabiliser 16 and the series
coil 18 becomes reduced and the current in the shunt coil 17 is increased owing to the rise in the battery
voltage, so that finally the shunt coil takes complete control of the regulation and reduces the charging
of the battery to a negligible amount.
The regulator shunt coil 17 and the series coil 18 are so wound that they assist each other, and the field
shunt coil is wound to oppose them. When the dynamo armature is revolving below cut--in speed the effects of
17 and 19 on the regulator piston 40 are nearly balanced so that it does not tend to move, but as soon as the
switch 6 is closed the series coil 18 assists the shunt coil 17. The piston 40 then begins to move and opens
the contacts l4 one at a time as the armature speed increases. As the contacts 14 are opened more of the
resistance 15 is inserted in the circuit of the dynamo field coil l and the coil 19. This gradual insertion
of resistance 15, which is not in itself new, just allows the voltage of the dynamo to be a little higher
than the battery volts, so that the charge is maintained as required. The coil 19 gradually becomes less
effective as the dynamo speeds up, owing to the reduction of the field current due to the insertion of the
resistance 15, the coils 17 and 18 thus becoming proportionately more effective.
The reverse takes place when the speed is reduced until all the contacts l4 are closed and the switch 6
opens and disconnects the dynamo from the battery. The opening of the switch 6 is quickened by the reversal
of the current in the series coil 9 when lamps are on due to the battery taking over the lamp load from the
dynamo. This partially demagnetises the cut-in switch piston 44, and assists it to fall more quickly at the
proper moment. Assume now that the lamps 30 are on and the dynamo is running, switch 29 being closed and
further that switch 6 has just been closed and switch 7 opened. The current now divides at the point 34,
part going to the battery as previously described and the remainder flowing through the lamp resistance 11
to the resistance switch 3 on to the main lighting switch 29 to the lamps 30 and returning to the negative.
The lamp current in passing through the lamp resistance 11 gives up part of its pressure or voltage so that
the lamps are now working at about 3 volts less than the battery voltage. This difference of voltage is
necessary so that the battery can be charged and at the same time the lamps not overrun. This state of
affairs continues until the lamp voltage has reached from 25 to 26 volts, due to the gradual rising of the
battery voltage.
At this moment several things happen in the following order :-
The control switch coil 24 being coupled to the point 31 in the positive lamp cable, current passes from
this point 31a through the coil 24 to the switch 5 and the resistance 32 to the negative pole. When the
voltage of the lamps rises to 26 volts this control coil 24 is sufficiently excited to raise its piston
45 Fig. 2 so that contact 22 is pressed against contacts 22a and 22b. Current now passes in three different
circuits each to perform a different duty . Firstly there is a circuit through contact 22a to a point 2la on
the resistance 21 continuing via 21c and the shunt regulator coil 17 to the negative pole. This strengthens
the regulator coil 17 as a part of the resistance coil 21 is now put in parallel to coil 8 and resistance 11
via switch 24, and the regulator therefore automatically inserts more field resistance l5 into the circuit
of the dynamo field coil 1 and slightly reduces the output.
Now return to contact 22b, some current passes the lamp resistance switch coil 4 and then through contact
13 and coil 35 to the negative pole. The function of this circuit is to cause a further lamp resistance 12
to be inserted in the lamp circuit by opening the switch 3. This causes a further drop of 3 volts so that
the lamps are now burning at about 6 volts less than the battery voltage. This ensures that the battery will
be fully charged even when all the lamps are in use.
Starting again from contact 22b, there is a circuit via control coil 25 and resistance 33 to the negative
pole. Due to self induction this coil 25 is not sufficiently excited to close switch 23\'before the
voltage drop referred to occurred, but when the voltage of the lamps rises to 26 again or perhaps to 26.5
to guard against coils 24,25 operating simultaneously said control coil 25 is strong enough to close contacts
23, current then passing from 22a to 23, then via 21b and 21c, shunt regulator coil 17 to the negative. This
still further strengthens the action of the main regulator as nearly all the resistance 21 is now short
circuited and more field resistance 15 is inserted, due to more contacts 14 being opened. This reduces the
dynamo charge to the battery, which should now be nearly charged.
Although the connection 31 is permanently made with the positive lamp cable, this positive cable is really
negative until the lamp switch 29 is closed.
There is no tendency for any current to flow through the
control 24 before the lamp switch 29 is closed. The control coil never operates except when the lamps are on.
As the train slows down the regulator gradually closes the contacts 14 in order from the right until contact
14a is reached, whereupon switch 13 is opened. In the present example contact 14a is the sixth from the left
Figs. 1, 2 and 3. This de-energises the coil 4 and closes switch 3 cuts out lamp resistance 12 while on
slowing still further switches 5 and 6 are opened and 7 is closed. This cuts out lamp resistance 11, and
the lamps are left to be maintained by the battery as long as switch 29 is closed.
The function of the resistance 2 will appear from the following:-
When the battery is well charged and
the dynamo is running at average speed, if a small lamp load should now be switched on it will be found
that the regulator is regulating at a lower voltage than the battery volts, which may be as high as 27 at
the moment. There will be a discharge from the battery to the lamps for a few minutes, and the dynamo
cut-out will operate and remain out until the peak of the battery voltage has discharged down to about
25 volts, when the regulator will function again as previously.
With small lamp loads the voltage drop through the lamp resistances 11 and 12 will not be noticeable and
as the regulator is now set at say 26 volts it will so reduce the dynamo field excitation that the cut-in
switch will cut out until the peak volts have fallen below 26.
When the battery voltage falls to about 25 the shunt coil 17 will release the piston 40 sufficiently to
close some of the contacts 14 and therefore increase excitation of the dynamo field circuit.
When the cut-out operates, the switch 5 is open, but sufficient current now passes through the resistance
2 to retain the piston 45 of the solenoid 24 in position until the switch 5 is again closed by the cut-in
solenoid. When cut-out occurs as the dynamo slows down the solenoid 24 remains sufficiently excited, due
to the current passing through the resistance 2 to keep switch 22 closed until the lamp voltage falls to 24.
This with full lamp load on takes place almost at the same instant as the cut-out occurs, but with a small
lamp load and a battery well charged it may take a few minutes before switch 22 is opened after the dynamo
ceases to generate.
When the dynamo is not generating, the lamp current passes from the battery positive to the series regulator
coil 18 and the stabiliser 16 to the series coil 9, then through switches 7 and 3, the lighting switch 29 to
the lamps 30 returning to the battery negative.
It will be observed that the lighting switch 29 is in the positive lamp circuit in this regulator, and it is,
therefore, no use taking a tapping for the controller 26 from anywhere along the lamp positive 31 as this is
negative as explained before excepting when the lamps are on.
When the controller 26 is operated positive current is derived from the positive terminal of the battery.
When the dynamo is running at normal speed and the lamps are switched on, the current taken by the lamps
does not reduce the charge to the battery, as each lamp switched on opens another easy path for the current,
the dynamo generating more current to meet the demand of the lamps at any time.
The circuit closed by switch 13 includes a coil 35 associated with the regulator coils 17, 18 and 19 the
function of which coil is to make the action of the switch 13 definite both when opening and shutting. As
it has a kicking effect on the regulator it is here termed a toggle coil. As soon as the current passes
through switch 13 the toggle coil 35 is energised and assists the shunt coil 17 to raise the piston 40,
thereby definitely closing the switch 13 and at the same time leaving the shunt coil 17 free to make further
adjustments when necessary.
When the speed of the dynamo is reduced the piston 40 gradually falls until the switch 13 is opened. This
de-energises the toggle coil 35 and causes the piston to make a slight further fall, which ensures that the
switch 13 is now well open.
The opening and closing of the contacts 13 takes place at about the same time as the sixth designated 14a
is operated. The main regulator contacts 14 and the switch contacts 13 are operated by the main lifting bar
of the regulator.
As will be seen from Figs 2, 3 and 4 the seven solenoids 4 (8-9-10)
(17-18-19-35-37), 24, 25, 27, 28, are all mounted on a single robust frame 47 which also carries the
remainder of the gear and is carried by feet 48 within a water and dust tight casing part of which 49 is
alone shown. In this way the parts are largely relieved of twisting strain. The switch 13 is a spring blade
having a natural bias towards an adjusting screw 50 and is moved away from the screw by the ordinary tapered
member 51 of the regulator which is operated by the solenoid piston 40 and serially disengages the contacts
14 from the common short-circuiting contact 52.
This contact 52 is given sliding movement without employing a separate magnet for this purpose, being
coupled by a link 53 to an arm 54 pivoted at 54a and encircled by a spring 55 against the returning action
of which it is moved, towards the right, by a lever 56 loosely engaged by the piston of the lights
"off" switch solenoid 27. Specifically the contact 52 is a length of carbon attached by screws 52a
to a carrier 52b of angle section mounted to slide on a support 52c of similar section and held against
separation therefrom by screws 52d, Fig. 3, the heads of which take into slots 52e in the support 52c.
It is to a lug on the carrier 52b that the link 53 is pivoted. The arrangement is such that the contact 52 is
reciprocated every time the lights "off" solenoid is energised and de-energised, in order to keep
the contacts clean. This movement of the contact is not in itself new and no claim is herein made to the means
now proposed for effecting the movement except as part of the system just described and set forth in the
principal claim.
When the lights "on" switch solenoid 28 is energised and the brush of switch 29 consequently
raised and closed such brush is held in raised position until solenoid 27 is energised, by a spring loaded
or gravity locking detent 57 pivoted at 58 the position of this pivot being so chosen that when thus in
engagement with the brush there is a natural tendency for it to be further drawn into a holding position
whereby a positive grip results which holds more firmly as pressure thereon is increased. Retraction of the
detent 57 is effected by a lever 59 which is depressed by an angle extension 60 of the lever 56 which angle
extension is depressed when the piston of solenoid 27 is raised. 62 is an emergency push for tripping the
piston of the solenoid 27 when it may be desired to manually open the switch 29.
Occasionally it may be desirable to couple lighting, battery and other mains through from coach to coach
where trouble may be experienced with belts, this being sometimes known as train lining. In these
circumstances half the dynamos of a train may fail, thus increasing the lighting load on the remaining
dynamos by l00 % which would most likely cause the dynamo fuses to blow unless their output is under control
with this special end in view. The output from the dynamo in such a case passes a series current limiting c
oil 37 associated with the regulator coils 17, 18, 19 and 35 and normally short circuited by a switch 36a
associated with a full load coil 36.
When the current reaches a predetermined amperage the coil 36 energises a piston connected to the switch
36a sufficiently to open the latter which now allows the current limiting coil to assist the regulator shunt
coil l7. The coil 37, switch 36a and coil 36 are not shown in Figs. 2 and 3 of the drawings but only in Fig. 1.
As most of the wear due to the action of the current takes place on the positive contact, the long main carbon
contact 52 has been made positive to the small lifting contacts l4, as it is more easily replaced and can be
turned to present new working faces, as it is rectangular in section. All the working faces of the regulator
contacts are in the vertical plane to allow dust to fall freely away.
Having now particularly described and ascertained the nature of my said invention and in what manner the same
is to be performed, I declare that what I claim is:
1. In an electrical system such as herein
referred to the combination with the exciting circuit of the shunt coil of the dynamo field regulator of a
resistance and control switches therefor so arranged that the shunt coil remains only slightly excited when
the accumulator alone is in circuit, or until the Amp voltage reaches a predetermined value if the lamps are
in circuit with an accumulator partially charged, at which time a section of resistance is shunted by a portion
of the lamp circuit to increase the excitation of the regulator shunt coil and reduce the excitation and
consequently output of the dynamo, to be followed by an equivalent shunting of a further section of resistance
when the lamp voltage rises again to the predetermined value or to a value slightly in excess thereof.
2. In an electrical system according to the preceding claim, dividing the series coil of the cut-in switch
into two equal sections, one section conducting the whole of the dynamo output current and the other section
only conducting the current to and from the battery, substantially as and for the purpose set forth.
3. In electrical system according to claim l, in which the circuit of one of the control switches is
maintained through a resistance connected in parallel with a switch associated with the cut-in switch in
the event of the dynamo cutting out when the battery charge is high and a small lamp load is switched on,
substantially as described.
4. In an electrical system according to claim 1, a resistance inserted in the lamp circuit in two stages,
the second half being controlled by a switch the operating solenoid circuit of which includes a switch
opened and closed when the regulator has been so influenced as to leave a predetermined number of its
movable contacts in engagement with the resistance short circuiting contact, substantially as and for
the purpose set forth.
5. In an electrical system according to claim 1 the provision upon the voltage regulator of a so called
toggle coil included in the circuit of a switch the opening and closing of which it is intended shall be
made definite when the regulator has been so influenced as to leave a predetermined number of the movable
contacts in engagement with the resistance short circuiting contact, substantially as and for the purpose
set forth.
6. An electrical system according to claim l, in which the resistance short circuiting
contact of the field regulator switch has a reciprocating movement imparted to it by operation of the
lights switch, substantially as described.
7. An electrical system according to claim 1 in which the series coil of the voltage regulator is shunted
by a low resistance stabiliser substantially as and for the purpose described.
8. In an electrical system according to claim l, a dynamo output limiting arrangement to prevent excessive
load on the dynamo when abnormal lamp loads are put in circuit, said arrangement including a limiting coil
only brought into use when the maximum permissible load has been reached, substantially as described.
9. A train lighting system substantially as described and shown in the accompanying drawings.
Mechanical Drawing
Electrical Drawing
Dated this 1st day of March, 1930. For the Applicant,
LLOYD WISE & Co.,
10, New Court, Lincoln\'s Inn, London
W.C. 2, Chartered Patent Agents.
