Improvements in and connected with the Control and Regulation of Electrically Propelled Vehicles.
Year: 1897

page_text: Date of Application, 11th Dec., 1897
Complete Specification Left, 10th Sept., 1898-Accepted, 26th Nov., 1898
PROVISIONAL SPECIFICATION.
Improvements in and connected with the Control and Regulation of
Electrically Propelled Vehicles.
EDWARD JOHN WADE, Engineer, and THE ELECTRIC MOTIVE POWER Co. LTD.,
both of 16, Elm Street, Gray's Inn Road, London, do hereby declare the nature
of this invention to be as follows:-
-
The object of our invention is to provide means for regulating & controlling
the running of electrically propelled vehicles whereby the motor or motors work
at a more uniform efficiency under all variations of load & speed than heretofore.
For this purpose we arrange devices to always maintain an efficient magnet-
ising current through the field coils when the vehicle is in use irrespective of
the amount of current that may be passing through the armature coils.
The method we employ for maintaining a proper current through the field
coils is to leave them in series with the armature in the usual manner & join
storage cells in shunt across their extremities, with the positive terminal of the
shunt cells opposed to the positive of the driving battery or other source of
electricity used.
The EMF, of the shunt cells should be so adjusted that when the current
in the main circuit is equal to that required to most efficiently excite the fields
their voltage just balances the difference of potential across the extremities of
the field coils, and consequently the whole of the current passes through them.
If however the current increases in the main circuit, the potential difference
across the field coils will rise in proportion, & the bulk of the surplus current
will be shunted through the cells. On the other hand, if the current in the
main circuit decreases the voltage of the shunt cells will over balance the
potential difference across the fields, & the cells will commence discharging
through them to make up the difference.
By this means the current through the field coils may be kept almost constant
provided the resistance of the shunt circuit is very low in proportion to that
of the fields. By increasing the resistance of the shunt circuit either with high
resistance cells or a resistance inserted in series with them, the current through
the field coils may be caused to automatically vary within certain limits rising
& falling with the armature current, but the range of variation must be limited
to those currents necessary for efficient working.
The capacity of the shunt cells may be small as they are only required to act
as regulators, giving out current at one time & storing it at another; but the
motor should preferably be so wound that the mean exciting current required
for the fields is somewhat below the mean current taken by the armature under
average running conditions. This device will ensure the shunt cells receiving
rather more current than they are called upon to supply, & they will therefore
always be maintained in a charged condition.
Separate contacts are provided on the controlling switches for closing the
shunt circuit before the main circuit.

page_text: A device, as for instance a dash pot should be provided to prevent the armature
being thrown into circuit too quickly before the magnetism of the fields has had
time to follow the rise of the exciting current.
Any suitable regulating device may be used in the armature circuit; but if
the propelling power is obtained from storage cells, the armature circuit may
preferably be controlled & the various speeds of the vehicle obtained by arrang-
ing them to be coupled up in various combinations of series & parallel, for
instance if twelve cells are used they may be coupled up in six parallels of two
cells each, 4 of 3, 3 of 4, 2 of 6, or all 12 in series, giving a range of running
speeds which it would be impossible to efficiently effect with a series machine
as ordinarily used for the reasons hereinbefore mentioned.
It is a useful feature of our invention that when the motor is being driven
by the vehicle as in descending hills, it is enabled to automatically exert a
considerable braking effect without any special devices for short circuiting the
machine through a resistance being required, & the current generated is returned
to the cells instead of being uselessly dissipated as heat.
Dated this Tenth day of December 1897.
For THE ELECTRIC MOTIVE POWER CO. LTD.,
A. W. SOUTHEY,
Managing Director.
Improvements in and connected with the Control and Regulation of
Electrically Propelled Vehicles.
ERNEST JOHN WADE, Electrical Engineer, of 84, Beechdale Road, Brixton Hill,
S.W., and THE ELECTRIC MOTIVE POWER CO. LTD., Motor Carriage Builders,
having registered offices at 17, Tower Royal, Cannon Street, London, E.C., late
of 16, Elm Street, Gray's Inn Road, London, W.C., do hereby declare the nature
of this invention and in what manner the same is to be performed, to be par-
ticularly described and ascertained in and by the following statement;-
The object of our invention is to provide means for regulating and controlling
the running of electrically propelled vehicles whereby the motor or motors work
at a more uniform efficiency under all variations of load & speed than heretofore.
For this purpose we arrange devices to always maintain an efficient magnet-
ising current through the field coils when the vehicle is in use, irrespective of
the amount of current that may be passing through the armature coils.
The method we employ for maintaining a proper current through the field
coils is to leave them in series with the armature in the usual manner and join
storage cells in shunt across their extremities, with the positive terminal of the
shunt cells opposed to the positive of the driving battery or other source of
electricity used.
The EMF. of the shunt cells should be so adjusted that when the current
in the main circuit is equal to that required to most efficiently excite the fields,
their voltage just balances the difference of potential across the extremities of
the field coils & consequently the whole of the current passes through them, and
none passes through or is given out by the shunt cells.
If however the current increases in the main circuit, the potential difference
across the field coils will rise in proportion, & the bulk of the surplus current
will be shunted through the cells. On the other hand, if the current in the

page_text: main circuit decreases, the voltage of the shunt cells will over balance the
potential difference across the fields, & the cells will commence discharging
through them to make up the difference.
By this means the current through the field coils may be kept almost constant
provided the resistance of the shunt circuit is very low in proportion to that
of the fields. By increasing the resistance of the shunt circuit either with high
resistance cells or a resistance inserted in series with them, the current through
the field coils may be caused to automatically vary within certain limits, rising
and falling with the armature current, but the range of variation must be limited
to those currents necessary for efficient working.
The capacity of the shunt cells may be small as they are only required to act
as regulators, giving out current at one time & storing it at another, but the
motor should preferably be so wound that the normal exciting current required
for the fields is somewhat below the mean current taken by the armature under
average running conditions. This device will ensure the shunt cells receiving
rather more current than they are called upon to supply, and they will therefore
always be maintained in a charged condition.
Separate contacts are provided on the controlling switches for closing the
shunt circuit before the main circuit, and a device as for instance a dash pot may
also be provided to prevent the armature being thrown into circuit too quickly
before the magnetism of the fields has had time to follow the rise of the exciting
current.
Any suitable regulating device may be used in the armature or main circuit,
but if the propelling power is obtained from storage cells, the armature circuit
may preferably be controlled & the various speeds of the vehicle obtained by
arranging them to be coupled up in various combinations of series & parallel
in the usual manner.
If the speeds of the vehicle are varied on a series-parallel" system in which
two or more motors or a single motor with two or more field & armature
windings are employed, each individual field circuit must be provided with a
separate set of storage cells in shunt with it so that as the field circuits are
thrown into parallel the sets of cells will be paralleled at the same time.
It is a useful feature of our invention that when the motor is being driven
by the vehicle as in descending hills it is enabled to automatically exert a
considerable braking effect without any special devices for short circuiting the
machine through a resistance being required. & the current generated is returned
to the cells instead of being uselessly dissipated as heat.
A similar braking effect is also obtained when the speed of the vehicle is
being reduced by the controller in the main circuit, for directly the driv-
ing E, M, F, is lowered, the motor is momentarily driven by the vehicle & acts
as a dynamo, sending a current in the reverse direction. In this way the vehicle
is slowed up almost immediately and its speed very rapidly brought down to
the normal one corresponding to the lower voltage acting on the armature.
These results entirely depend on the magnetism of the fields being properly
maintained by the shunt circuit, and could not be obtained with series wound
motors as ordinarily used, for it is well known that either their field connections
or the direction of rotation of the armature must be reversed before they can
act as dynamos.
Their efficiency also varies very largely with the load, for with small currents
their magnets are insufficiently excited and with currents above those necessary
to nearly saturate them a large amount of energy is wasted in heating the field
coils.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that
what we claim is;-

page_text: or motors, and storage cells joined in shunt across their field coils, the EMF
of the cells & the resistance of the coils being so proportioned in relation to each
other that when the normal magnetising current is passing through the main
circuit, no current is flowing into or being given out by the shunt cells, substan-
tially as and for the purposes set forth.