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Sept. 10, 1946.
z_ Q_ 51' PALLEY
2,407,521
ELECTRIC PROTECTIVE SYSTEM
Filed Oct. 1, 1945
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Inventor‘:
Zolt an O. StPalley;
by His Attorney.
_
Patented Sept. 10, 1946
2,407,521
UNITED STATES PATENT OFF-ICE
2,407,521
‘ELECTRIC PROTECTIVE SYSTEM
Zoltan 0. St..Palley, Pitts?elkL'Mass” ass'ignor to
General ' Electric
‘New York
Company, a corporation of
Application Octoberv 1, 1943, Serial No. 5045575
3 Claims.
1
((31. ‘105—51)
2
My invention relates to electric protective sys~
terms for alternating current motors, and, more
particularly, to systems for protecting a plurality
of alternating current electric traction motors
against wheel slippage. The invention has for its
principal object the provision of a new-and im
proved protective system of-this type which re
quires only a minimum of apparatus, but func
?gure of which is a diagrammatic representation
of my invention as applied to an electrically
operated vehicle, such as an electric locomotive.
Referring vnow to the drawing, I have shown
an alternating current supply transformer hav
ing a primary winding l0 with one terminal
grounded at I l and the-other terminal connected
through a ,pantograph l2 ‘to a supply conductor
tions with optimum e?iciency and reliability.
In the operation of a plurality of electric motors 10 [3. The supply transformer is provided also with
a secondary winding 14 'having one terminal
separately connected to the driving axles of a
grounded at E5 and having at its other end two
vehicle, one pair of wheels connected to an axle
electrically spaced voltage taps i6 and H. To
sometimes slips on the track, especially when
facilitate motor starting the grounded end of the
rapid acceleration is attempted under heavy load
conditions. ‘When this slipping occurs, the motor
transformer winding .lll may, if desired, 'be pro
vided with a plurality of taps £8 to which the
connected to the slipping axle accelerates to a
higher speed than the other motors and may
reach a speed causing damage to the accelerated
motor on account of the resulting high mechan
motor circuit is sequentially connected by means
of a suitable manually operable accelerating con
troller diagrammatically illustrated as a slider
i9.
ical stresses. Furthermore, when the traction
'To the secondary winding M of the supply
motors are connected for energization in parallel
transformer
there are‘ connected three conductors
circuit relation, the slipping of one pair of wheels
2U, Z'Land 22 "for connecting a plurality of elec
relieves the connected motor of any substantial
tric ‘traction motors in parallel circuit relation.
portion of the load so that the remaining motors,
While
conductors 21 and 22 are electrically
connected to non-slipping wheels, may stall or 25 spaced the
apart in potential by reason of the spac
may be damaged'by high overload currents.
ing or the taps l6 and i‘l,'the potential difference
between the conductors 2| and 22 is small in
‘In carrying out my invention, I provide an
alternating current supply transformer having
at‘leas‘t'two‘variable'voltage taps and arranged
relation to that between either one of these
to supply'current to a' plurality of traction motors 30 conductors and the ‘conductor ‘28. Accordingly,
I wish to have ‘it understood that for the pur
or‘trac’tion groups connected inparallel circuit
poses
of this speci?cation, the term “parallel
relation. Separate selector switching means are
circuit
relation” shall be understood to mean
provided in connection'with‘each‘motor or motor
connections'between the conductor 20 and. either
group‘under the control of a wheel slippage de
tecting device, such‘as'a diiferential speedometer,
for controlling each selector switch independent
35
one of the conductors 2| or 22,
A pair of series type electric traction motors
having armatures 23 and 24 and series ?eld wind
ings 25 and 26, respectively, are connected in
tap on'the transformer in ‘accordance with slip
parallel circuit relation across the transformer
page conditions of that motor. Preferably, and to
preclude vopen-circuiting of any‘motor, the selec 40 secondary winding Hi. It will be understood
that the 'motor armatures 23 and 215 are sep
tor switch associated with 'each‘moto-r or motor
arately connected to independent driving axles
group is so arranged that'at the instant ~of trans
ofan electric vehicle (not shown). One terminal
fer the terminals of the variable ‘voltage "taps
of :each of the traction motors is connected t0 the
are‘bridged. In order to‘ prevent short-circuiting
of @the transformer between taps at the ‘instant 45 conductor 20. The otherterminals of the motors ‘
are ‘connected to separate tap changing. or selector
of transfer a current limiting impedance is inter
switches 21 and 28. ‘The selector switch 21 is
posed between the transformer'and'the'?rst con
associated with the ‘traction motor '23, 25 and
nected switching'means-in such a position‘that
comprises a pair of fixed contacts '29 and 30
it ‘serves to prevent short-circuiting of the var
connected,
respectively, to the conductors 2| and
iable voltage tapsiby any of'the connected'switch 50
22 and moving ‘contact 3!. ‘Similarly, the tap
ing means.
changing switch 28 comprises a pair of ?xed
For a more ‘complete understanding of my
contact
members 32 and 33 connected, respec
invention, reference ‘should now 'be had to the
tively,‘to the conductors '2! and 22 and a moving
following ‘detailed'speci?cation taken'in conjunc
contact '34. To ‘prevent short-circuiting of the
tion with the accompanying-drawing, the single
ly to connect each motorto a high or low voltage
transformer "taps “l?‘and I1 ‘I provide in one'of
2,407,521
3
1i
the fluid motor 36 so that the selector switch 21
is moved ‘back to the position shown in the
the wires if or 22 between the supply transformer
and the first connected selector switch a current
limiting impedance, such as a reactor 35 in the
conductor 2 l.
The selector switches 21 and 2B are each actu
drawing.
In view of the foregoing description, it will now
be evident that I have provided a wheel slippage
protective system for an electric vehicle driven
ated by a separate differential speed responsive
mechanism which compares the speed of the as
sociated traction motor or driving axle with a
standard speed, such as that of an idler wheel
upon the vehicle. It will be understood that the 10
particular form of such differential speed respon
by parallel connected alternating current motors
which is not only new and novel, but is particu
larly attractive because of its simplicity and se
lectability. My system not only provides com
plete and independent protection for each trac
sive mechanism is not an essential feature of
my invention. For the purpose of illustration I
tion motor or motor group, but it does so with
a minimum amount of switching equipment. It
have shown the tap changing switches 21 and
28 connected for actuation by suitable valve-con;
trolled air or fluid motors 36, 31, respectively, the
fluid motor valve being controlled by suitable
er and the traction motors, and that only a single
will be particularly noted that only three electric
conductors extend between the supply transform
current limiting impedance is needed to provide
short-circuit protection for all or any one of the
electromagnetic relays 38, 39, respectively, which
motor tap changing switches.
are in turn controlled, respectively, by contact
making differential speedometers 40 and 41.
The differential speedometer 40 is connected be
tween the wheel or axle driven by the motor 23,
20
.
While I have illustrated only a single preferred
embodiment of my invention by way of illustra
tion, many further modi?cations will occur to
those skilled in the art and I therefore wish to
have it understood that I intend in the appended
25 and suitable idler wheel 42 to detect slipping
of the associated driving wheel, while the differ
ential speedometer 41 is connected between the 25 claims to cover all such modi?cations as fall with
in the true spirit and scope of my invention.
wheel or axle driven by the motor 24, 26 and an
What I claim as new and desire to secure by
idler wheel 43 for a like purpose. It will of course
Letters Patent of the United States is:
be understood that, if desired, both differential
1. A protective system for independently pre
speedometers may be connected to the same idler
venting excessive overspeeding of each of a plu
wheel.
rality of driving axles of an electrically driven
I wish to have it understood also that, while I
‘vehicle with respect to an idler wheel of said
have shown single motors 23, 25 and 24, 26 con
vehicle comprising a plurality of alternating cur
nected in parallel circuit relation across the sec
rent traction motors separately connected to said
ondary winding it of the supply transformer, it
driving axles, a supply transformer having a plu
is within the scope of my invention tosubstitute
rality of voltage taps, separate switching means
for each of these motors a group of motors con
for
connecting one terminal of each of said mo
nected in series or parallel circuit relation with
tors independently to selected taps of said trans
respect to each other.
former, differential speed responsive means con
In view of the foregoing explanation of the
construction and arrangement of the various 410 nected between an idler wheel and each of said
driving wheels for independently controlling each
parts of my invention, it is believed that its mode
of said switching means to select said taps, and
of operation will be clear from the following
means connecting the other terminals of said
brief description. Let it be assumed that the
motors together and to selectable taps upon said
motors have been energized by proper actuation
_
of the accelerating controller I9 and that the 45) transformer to accelerate said motors.
2. A protective system for independently pre
wheels connected to the armature 23 begin to
venting excessive overspeeding of each of a plu
slip. With such slippage and loss of traction, the
rality of driving axles of an electrically driven
armature 23 speeds up very rapidly and causes
vehicle with respect to an idler wheel of said
actuation of the relay 38 through the differential
speedometer £16. When the relay 38 is operated, 50 vehicle comprising a plurality of alternating cur
rent traction motors separately connected to said’
the air or fluid motor 36 actuates the moving
driving axles, a supply transformer having a sec
contact 3| of the selector switch 2'! from the high
ondary winding provided with a plurality of var
voltage tap 33 to the low voltage tap 29 thereby
iable voltage taps at each end thereof, means for
to reduce the voltage applied to the traction mo
connecting one terminal of each of said motors
tor 23, 25 without affecting the voltage applied
together and to selective taps at one end of said
to the traction motor 2%, 26. It will be noted
secondary winding to accelerate said motors, sep
that the contact 3| is so constructed that at the
arate selector switching means for independently
instant of transfer of connections from the con
connecting the other terminals of each of said
tact
to the contact 29 the two stationary con
tacts 29 and 353 are bridged by the moving contact 60 motors to a selected one of said voltage taps at
the opposite end. of said secondary winding, and
3|. At this instant, the variable voltage taps i6
differential speed responsive means connected be
and il on the transformer winding M would be
tween an idler wheel and each of said driving
‘ 1 short-circuited were it not for the current limit
ing impedance 35. It will also be noted that, by , axles for controlling each of said selector switches
reason of the interposition of the impedance 35 65 independently to reduce the voltage applied to
any slipping motor.
between the transformer tap H and the first con
3. A protective system for independently pre
nected tap changing motor switch, the impedance
venting excessive overspeeding of each of a plu
35 serves to prevent short-circuiting of the trans
rality of driving axles of an electrically driven
former tap by any of the connected motor tap
vehicle with respect to an idler wheel of said
changing switches.
vehicle comprising a plurality of alternating cur
The reduced voltage thus applied to the motor
rent traction motors separately connected to said
23, 25 reduces the torque of this motor and pre
driving axles, a single supply transformer having
vents further slipping of the wheels. As soon as
a first terminal and at least two voltage taps dif
the wheel slip is stopped, the differential speed
ferently spaced therefrom in potential, means for
ometer "it and control relay 38 effect reversal of
5
2,407,521
connecting one terminal of each of said motors
to said ?rst terminal of said transformer, sepa
rate selector switching means for independently
connecting the other terminals of each of said
motors to a selected one of said voltage taps of
said single transformer, di?erential speed re
sponsive means connected between an idler wheel
and each of said driving axles for controlling each
of said selector switches independently to control
the voltage applied to said motors, and a cur
rent limiting impedance interposed between at
least one of said voltage taps and said switching
means to prevent short-circuiting of said trans
former between said taps upon actuation of said
switching means.
ZOLTAN 0. ST. PALLEY.
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