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BACKGROUND OF THE INVENTION
This invention relates tO a multiple speed dynamoelectric machine, and more
particularly to a multiple speed permanent split capacitor (PSC) or other
capacitor-run multi-speed induction motor, such as may be utilized to
directly drive a fan mounted on the rotor shaft of the motor.
Generally, in a motor application for use with a direct drive overhead
ceiling fan or the like, the motor is designed to run at a relatively slow
speed. For example, a multiple-speed overhead ceiling fan motor may be
operated at a maximum speed of about 350 rpm and at a minimum speed of
about 50 rpm. These motors generally are multiple pole motors having
either 12 or 18 poles, as compared to more conventional 2, 4, 6, or 8 pole
motors. A PSC motor is a capacitor run motor that uses its auxiliary
winding and capacitor continuously, without change in the capacitance. No
starting switch or relay is required to switch out the auxiliary winding
of the motor once the motor has attained its operational speed. Typically,
a PSC motor comprises a main winding adapted to be connected across two AC
power lines. An auxiliary winding and a permanent running capacitor are
wired in parallel to the main winding so that upon energization of the
windings, the main winding and the auxiliary winding are spaced 90
electrical degrees apart. A squirrel-cage-type rotor is usually utilized
in PSC induction motors.
In a number of PSC fan motor applications, it is highly desirable to
provide for multiple speed operation of the fan motor. Speed control of a
PSC motor is typically obtained by adjusting the flux of the motor and
thereby changing the slip. As a general rule, pole changing is not
utilized with PSC motor applications. There are four basic methods of
changing the flux of the stator and thereby changing the slip and
operating speed of a PSC motor. A first method of speed control of a PSC
motor utilizes a change of connections of the main windings. Secondly, the
voltage impressed on one or both the main and the auxiliary winding may be
changed. Thirdly, an external impedance or capacitance may be placed in
series with the main winding of the motor. And, fourthly, various tapping
methods using autotransformers and secondary main windings are used.
Looking first at voltage change methods for speed control, these methods
typically employ a simple autotransformer used in conjunction with the PSC
motor such that the voltage on both the main winding and the auxiliary
circuit (i.e., the permanent capacitor and the auxiliary winding) is the
same at all times, but the actual voltage applied to the main and
auxiliary windings is varied depending on the tapping point of the
autotransformer.
In utilizing voltage changes for speed control purposes, the PSC motor is
normally operated at its high speed mode of operation when the full
voltage of the AC power supply is utilized to energize both the main and
auxiliary windings of the motor. For example, in an overhead ceiling fan
motor application using voltage speed control, the full AC line voltage
(120 volt) would be impressed across the windings resulting in high speed
operation of the motor (e.g., 350 rpm). For medium speed operation of the
motor, the autotransformer in parallel with the main and auxiliary
windings is tapped at an intermediate point so as to reduce the voltage
impressed on both the main and auxiliary windings with a corresponding
speed-torque curve reduction such that the torque of the motor is less
than at its high speed operation with the drag or slip of the fan blades
resulting in a steady state operating speed of the motor slower than its
high speed mode of operation. Likewise, slower speed modes of operation
may be obtained by further reducing the voltage (and hence the torque) of
the motor. In voltage speed control systems, the operating speed of the
motor generally depends on the load applied to the motor. Also, the locked
rotor torque of the motor is necessarily low when the motor is operated at
its low speed mode of operation and the low speed connection is inherently
unstable because the fan-torque and motor-torque curves intersect one
another at a very small angle such that the motor is sensitive to changes
in voltage and in load.
If an external impedance is utilized for speed control purposes, the
impedance typically is either a resistor or a reactor which is connected
in series with the main winding such that the voltage impressed across the
main winding is reduced when the impedance is connected in series to the
main windings thereby reducing the flux and increasing the slip of the
motor and in turn reducing the operating speed of the motor. In the
coassigned U.S. Pat. No. 4,408,150, a capacitor is interconnected in
series with the main winding of the motor and which, when serially
connected to the main winding of the motor, results in a reduction in
speed of the motor.
In tapped winding speed control arrangements, such motors typically effect
speed control by flux control, accomplished primarily by changing the
impressed volts per turn on the main winding. Generally, tapped winding
motors vary the volts per turn (and hence the flux, slip, and speed of the
motor) by changing the number of series conductors in the main winding.
For example, a two speed tapped winding motor utilizes three windings
including a main winding, an extra main or intermediate main winding, and
an auxiliary winding. The main and intermediate main windings are wound in
space phase with one another (i.e., one is wound on top of the other) in
the same slots, with the same distribution but not necessarily with the
same number of turns or wire size. For more than two speeds, the
intermediate main winding itself is tapped.
In a recently commercially available PSC direct drive fan motor, only one
main winding was provided and the auxiliary winding was tapped at
different locations. Through the use of a double pole, triple throw speed
selector switch, selected physical poles of the auxiliary winding could be
electrically removed from the remainder of the auxiliary winding in
parallel with the main winding, or the tapped auxiliary winding could be
utilized as a voltage divider thereby to change the flux impressed upon
the windings of the motor. However, because one or more of the physical
poles of the auxiliary winding of this motor is not energized at the
intermediate or slower speeds of operation of the motor, the flux
distribution of this motor is not balanced around the stator core and this
unbalanced magnetic flux results in noisy operation of the motor at slower
speeds.
SUMMARY OF THE INVENTION
Among the several objects and features of the present invention may be
noted the provision of a multi-speed induction motor and method of speed
control therefor which enables multiple speed operation of the motor, but
yet which does not require the use of autotransformers, external
impedances, external capacitors, or additional main windings, and yet
results in a balanced flux distribution at all of its operational speeds;
The provision of such a motor and method which significantly lessens the
amount of magnet wire required for the windings of the motor (as opposed
to prior art tapped winding speed control methods using intermediate main
windings);
The provision of such a motor and method which utilizes a single pole speed
selector switch thus enabling a motor of the present invention to replace
existing multi-speed motors without the necessity of changing the
switching network;
The provision of such a motor which has a significantly lower slot fill and
which has windings which are relatively easy to insert in the slots of the
stator core during manufacture;
The provision of such a motor which eliminates the necessity of a fast
acting thermal protector switch for protecting the windings of the motor
against overheating in the event the motor capacitor fails is a shorted
condition; and
The provision of such a motor and method which has a lower production cost
than other multi-speed PSC motors, which is reliable in operation, and
which is quiet in operation at all operational speeds.
Briefly stated, a multiple speed electrical induction motor of the present
invention has a stator core comprising a stack of laminations of suitable
ferromagnetic material. The core has a central bore extending therethrough
and a plurality of slots extending generally radially outwardly from the
bore. A rotor is rotatably received within the bore and windings are
inserted in the stator slots, these windings comprising a main winding and
an auxiliary winding. A capacitor has one side thereof connected in series
with the auxiliary winding. The auxiliary winding is comprised of a
plurality of coil sets with each coil set having a plurality of serially
connected coils placed in the stator core slots at substantially equal
angular intervals around the central bore of the core so as to constitute
the poles of the windings. A first tap point is provided between the first
and second coil sets of the auxiliary winding and a last tap point is
provided between the last of the coil sets of the auxiliary winding and
the main winding. A pair of power lines is connected to a source of
alternating current power, with one side of the main winding and the other
side of the capacitor being connected to one side of this power source,
and with the auxiliary winding being connected to the other side of this
power source. A speed selector switch is provided having a movable switch
arm or member which is connected to the other side of the main winding,
this switch arm being movable between a high speed position in which a
maximum number (e.g., all) of the coil sets of the auxiliary winding is
energized in series with the capacitor, and in which the maximum number of
coil sets of the auxiliary winding, the capacitor, and the main winding
are in parallel with the other side of the power source such that the
motor operates in its high speed mode of operation. The speed selector
switch is further operable in a low speed position in which a minimum
number of coil sets of the auxiliary winding (e.g., one such auxiliary
coil set) is connected in series with the capacitor, and in which the
minimum number of auxiliary coil sets, the main winding, and the capacitor
are in parallel with the other side of the power source such that the
motor operates at a slow speed mode of operation.
Other objects and features of this invention will be in part apparent and
in part pointed out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of a portion of an overhead ceiling fan
illustrating a multiple speed permanent split capacitor (PSC) motor of the
present invention and a speed selector switch with portions broken away to
show details of construction of the motor and the switch;
FIG. 2 is an end view of a portion of a stator of an 18 pole, 2 speed PSC
skein wound motor having a single main winding divided into two main
winding coil sets and a single auxiliary winding divided into two
auxiliary coil winding sets with the coils of the main and auxiliary coil
sets being inserted into the slots of the stator core in layered groups to
constitute the physical poles of the motor;
FIG. 3 is a diagrammatic view of the windings shown in FIG. 2, but from the
opposite end of the stator core shown in FIG. 2;
FIG. 4 is a schematic of the windings shown in FIGS. 2 and 3;
FIG. 5 is a diagrammatic view, similar to FIG. 3, of a stator for a 12
pole, 2 speed PSC motor having a single main winding divided into two main
winding coil sets and a single auxiliary winding which is also divided
into two auxiliary winding coil sets with the coils of the main and
auxiliary coil sets being inserted into the slots of the stator core in
layered groups;
FIG. 6 is a schematic of the windings shown in FIG. 5;
FIG. 7 is a diagrammatic view, similar to FIGS. 3 and 5, of a 12 pole, 4
speed PSC motor having a single main winding divided into two main winding
coil sets and a single auxiliary winding divided into four auxiliary
winding coil sets with the coils of the main and auxiliary windings being
inserted into the slots of the stator core in layered groups each
comprising two main winding coils and four auxiliary winding coils with a
plurality of tapping points for the selective energization of each of the
auxiliary coil subsets.
FIG. 8 is a simple schematic of the windings and leads shown in FIG. 7;
FIG. 9 is a schematic of the motor windings of FIG. 7 more detailed than
FIG. 8 with the auxiliary coil sets shown as four separate auxiliary
coilsets with the tapping points therebetween for connection to a source
of AC power via a selector switch such that at a high speed switch
position, all of the coil sets of the auxiliary winding are energized in
series with the capacitor and the motor operates at its high speed mode of
operation, such that at a low speed switch position, only one of the
auxiliary winding coil sets is energized in series with the permanent
capacitor and the other auxiliary coil sets are in series with the main
windings such that the motor operates at its slow speed mode of operation;
FIG. 9A is a still more detailed schematic of FIG. 9 showing that each of
the auxiliary coil subsets has a number of (e.g., six) serially connected
coils therein which are uniformly distributed around the stator core at
generally equal angular intervals so as to result in balanced running of
the motor at any of its selected operating speeds;
FIG. 10 is a schematic similar to FIG. 9 of the motor windings shown in
FIG. 7, but with the selector switch connected to the auxiliary winding
coil sets in a different manner than is shown in FIG. 9:
FIG. 10A is a more detailed schematic of FIG. 10;
FIG. 11 is a schematic similar to FIGS. 9 and 10 of the motor winding shown
in FIG. 7, but with the selector switch connected to the auxiliary winding
coil sets in still a different manner;
FIG. 11A is a more detailed schematic of FIG. 11;
FIG. 12 is a schematic of a typical prior art PSC four speed motor having a
first main winding, an auxiliary winding connected in parallel to the
first main winding with a capacitor therebetween, and three intermediate
or booster main windings in series with the first main winding, these
intermediate main windings being selectively connectable to the first main
winding thereby to progressively slow down the operating speed of the
motor as more of the intermediate main windings are serially connected to
the first main winding;
FIG. 13 is a schematic of a four speed PSC motor of the present invention
in which the auxiliary winding is divided into four coil sets each having
a plurality of coils which are uniformly distributed around the stator
core so that with the speed selector switch in its high speed position,
all of the auxiliary winding coil sets are in series with the capacitor
and in parallel connection with the main winding, and such that with the
speed selector switch in one of its intermediate or slow speed mode of
operation, one or more of the auxiliary winding coil sets is in series
connection with the capacitor and parallel to the main winding and such
that the other auxiliary winding coil sets are in series connection with
the main winding such that the motor operates at a slower speed mode of
operation; and
FIG. 14 is a diagrammatic view of still another embodiment of the windings
of a motor of the present invention.
Corresponding reference characters indicate corresponding parts throughout
the several views of the drawings.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, and particularly to FIG. 1, a dynamoelectric
machine of the present invention is indicated in its entirety by reference
character 1. Specifically, this dynamoelectric machine is shown to be a
multiple-pole, multiple-speed permanent split capacitor (PSC) induction
motor. While the motor 1 utilizing the speed control system, construction
and method of the present invention is herein described as a PSC motor,
those skilled in the art will appreciate that this invention will have
applications in other types of motors (e.g., other capacitor run motors)
and that the multiple-pole (e.g., 12 and 18 pole) motors herein described
may have significantly fewer poles.
More specifically, motor 1 has a stator assembly 3. The stator is comprised
of a core 5 made up of a stack of laminations of suitable ferromagnetic
material. The core 5 has a central bore 9 extending longitudinally
therethrough with a plurality (e.g., thirty six) slots 11 extending
radially outwardly from central bore 9 and with a plurality of teeth 13
separating the slots. As shown in FIG. 2, core 5 has thirty-six slots 11
formed therein (as indicated by slots S1-S36) with a respective tooth 13
(as indicated by T1-T36) between each of the slots.
Motor 1 further includes windings, as generally indicated at W, which are
inserted into slots 11 with these windings having end turns E extending
out beyond the end faces of core 7, as shown in FIGS. 1 and 2. The motor
further includes a rotor assembly, as generally indicated at 15, having a
squirrel cage rotor body (not shown) which in turn has a hollow rotor
shaft 17 extending endwise from the motor and with the rotor shaft being
rotatable with the rotor body. The stator assembly 3 further includes a
housing or shell 19 surrounding core 5 and extending out beyond the end
turns E of the windings W. An end shield 21 is bolted to each end of the
core 5 and to shell 19 and has a bearing support (not shown) formed
therein for receiving a ball bearing or the like (also not shown) which in
turn receives and journals rotor shaft 17 thereby to accurately, rotatably
support the rotor assembly 15 within central bore 9 of stator assembly 3.
On the portion of rotor shaft 17 extending endwise beyond end shield 21, a
hub 23 is locked to the rotor shaft so as to be rotatable with the rotor
shaft. In an overhead ceiling fan application, the paddle fan blades (not
shown) of the overhead ceiling fan may be affixed to hub 23 such that the
fan blades rotate with the rotor shaft 17.
As previously indicated, rotor shaft 17 is a hollow tubular member and it
has a wireway 25 extending axially therethrough, this wireway being
stationary with respect to the rotor shaft. A nut 27 is threaded onto the
free end of wireway 25 and this nut holds a switch housing 29 in place on
the lower end of the wireway. The wireway 25 is a tubular rod-like member
and serves as a conduit through which various lead wires 31 are run to a
multiple position speed selector switch, as generally indicated at 33,
located within switch housing 29. In accordance with this invention,
selector switch 33 may be a single pole, multiple throw switch having a
switch arm SA operated by means of a pull chain 35 so as to selectively
operate motor 1 at any one of a multiplicity of operating speeds. The lead
wires 31 extend longitudinally through wireway 25 to the opposite end of
the motor from that shown in FIG. 1 and the various lead wires are
connected to an alternating current power source by power supply leads Pl,
P2 for supplying AC electrical power to selected portions of the windings
W of the motor in accordance with the apparatus and method of this
invention, as will be more particularly pointed out hereinafter.
Referring now to a more detailed description of windings W of motor 1, in
general, the windings of a motor in accordance with the instant invention
comprises a main winding, as generally indicated at M, and an auxiliary
winding, as generally indicated at A. As shown in FIG. 2, the main winding
M of the stator assembly 3 is constituted by two main winding coil sets,
as indicated at MC1 and MC2. Likewise, the auxiliary winding A is
constituted by two auxiliary coil sets, as indicated at AC1 and AC2.
Stator assembly 3 illustrated in FIG. 2 is an eighteen pole skein wound
winding inserted in the slots of a thirty six slot stator core 5. Such a
skein wound coil set for either the auxiliary or main winding may be
formed on a skein coil former, such as is disclosed in the coassigned U.S.
Pat. No. 4,357,968, issued to Vernon E. Kieffer which is herein
incorporated by reference. Additionally, the main coil sets and the
auxiliary coil sets are inserted in the slots 11 of core 5 in layered
groups of coils in the manner is described in the copending and coassigned
U.S. Pat. No. 4,426,771, which is also herein incorporated by reference.
Thus, a detailed disclosure of the manner in which the coil sets MC1, MC2,
AC1 and AC2 are inserted in the slots 11 of core 5 may be had by making
reference to the disclosure of the last-mentioned U.S. Pat. No. 4,426,771.
Moreover, while the windings shown in FIG. 2 were heretofore described as
being skein wound coil sets, it will be understood, particularly when
reference is had to the above-mentioned U.S. Pat. No. 4,426,771, that the
windings W may be so-called concentric wound coils inserted in the slots
of the stator core in an overlapping insertion pattern in accordance with
the method described in U.S. Pat. No. 4,426,771. It will also be
understood that the windings W of stator assembly 3 may be skein wound and
formed such that each of the coils of the coil sets of both the main and
auxiliary windings span an equal number of teeth, such as disclosed in the
co-assigned U.S. patent application Ser. No. 471,831 to Stephen M. Breit,
which is also herein incorporated by reference.
Referring now to FIGS. 3 and 4, the pattern of the layered groupings of the
main and auxiliary winding coil sets illustrated in FIG. 2 can be more
easily seen. As heretofore explained, stator assembly 3, as shown in FIG.
3, is an eighteen pole winding inserted in stator core 5 having thirty-six
slots S1-S36 with the windings being inserted in nine layered groupings of
alternating coils of the auxiliary and main windings A and W so as to
constitute the physical poles of the stator with these layered groupings
being substantially equally angularly distributed around the core. More
specifically, the first coil set AC1 of auxiliary winding A is shown to
comprise a plurality (e.g., nine) of serially connected coils, as
indicated at AC1a-AC1i. Likewise, the first main winding coil set MC1
comprises a plurality (e.g., nine) of serially connected coils, as
indicated at MC1a-MC1i. Still further, the second main winding coil set
MC2 comprises nine serially connected coils, as indicated at MC2a-MC2i,
and the second auxiliary coil set AC2 comprises nine serially connected
coils, as indicated at AC2a-AC2i.
As shown in FIG. 4, the main winding coil sets MC1 and MC2 are serially
connected and thus form a continuous main winding M. Further, auxiliary
winding coil sets AC1 and AC2 are connected in series with a first tap
point TP1 therebetween connected to a respective leadwire L1 which extends
out of the motor shell, down through wireway 25 for connections to the
appropriate terminals of selector switch 33 for purposes as will appear.
Another or last tap point, as indicated at TP2, is provided at the
opposite end of the second or last auxiliary coil set AC2 and has a
respective leadwire L2 connected thereto which extends exteriorily of the
motor through the wireway for connection to selector switch 33. A
permanent running capacitor, as indicated generally at C, is serially
connected to the auxiliary winding A and, together with the auxiliary
winding, is in parallel to main winding M.
As has been previously pointed out, each of the auxiliary winding coil sets
AC1 and AC2 comprises a plurality of series connected coils, as indicated
at AC1a-AC1i and AC2a-AC2i, respectively. In accordance with this
invention, in the high speed mode of operation, 120 volt AC electrical
power is connected to tap point TP2 via the leadwire L2 such that both of
the auxiliary winding coil sets AC1 and AC2 together with capacitor C are
connected in parallel with the entire main winding M to the other power
input lead Pl whereby the motor 1 of the present invention operates in its
high speed mode of operation. When it is desired to selectively switch the
speed of motor 1 from its high speed mode of operation to its slow speed
mode of operation, AC electrical power is removed from the last tap point
TP2 and is applied to the first tap point TP1 via the leadwire L1. In this
condition, capacitor C and only the first auxiliary winding coil set AC1
are connected in parallel to the main winding M. It will be noted that the
second auxiliary coil set AC2 is now in series with the main winding M and
thus constitutes a part of the main winding. It will be further be noted
that in both the high and low speed modes of operation, the energized
coils of the auxiliary winding (whether only the first auxiliary winding
coil set AC1 or both of the auxiliary winding coil sets AC1 and AC2 are
energized), the coils are uniformly distributed around the stator core 5
at generally equal angular intervals so as to result in a balanced flux
field for the motor which in turn results in quiet operation of the motor.
It will also be noted that the speed control system of the present
invention accomplishes effective speed control in a balanced fashion
without the necessity of external inductive reactors, without the
requirement of external capacitors, and without the requirement of
additional intermediate main windings inserted in the slots of the stator
core thereby resulting in a considerable savings of materials, in a lower
slot fill for the motor, and resulting in a substantial savings in the
amount of copper magnet wire required to form the windings W of the motor
1.
Referring now FIGS. 5 and 6, another stator assembly, as generally
indicated at 3', is shown for another embodiment of a motor in accordance
with this invention. It will be understood that the "primed" reference
characters in regard to FIGS. 5 and 6 denote parts having a corresponding
construction and function to corresponding parts heretofore described in
regard to FIGS. 1-4. Generally, the primary difference between the stator
assembly 3, as shown in FIGS. 3 and 4, and the stator assembly 3', as
shown in FIGS. 5 and 6, is that stator assembly 3 is for an eighteen pole,
two speed motor whereas the stator assembly 3' is for a twelve pole, two
speed motor. In each instance, the stator cores 5 and 5' each include
thirty-six radial core slots S1-S36 and S1'-S36', respectively Since the
construction and operation of stator 3' is generally similar to stator 3,
as heretofore described, a detailed description of the construction and
operation of the twelve pole, two speed PSC motor, as illustrated in FIGS.
5 and 6, will not be herein repeated for the sake of brevity.
In FIGS. 7 and 8, still another embodiment of a stator assembly, as
indicated at 3", incorporating the speed control system and method of the
present invention is depicted. Generally, stator assembly 3" is intended
for use in a twelve pole, four speed PSC electric induction motor. The
"double primed" reference characters indicate parts having a corresponding
construction and function to corresponding parts heretofore described in
regard to the stators 3 and 3' shown in FIGS. 3 and 4 and in FIGS. 5 and
6, respectively. A primary difference between stator assembly 3" and
stator assembly 3' is that the auxiliary winding A" has four auxiliary
winding coil sets, as indicated at AC1"-AC4", whereas the auxiliary
winding A' of stator 3' only has two auxiliary winding coil sets AC1' and
AC2'. Even more specifically, each of the auxiliary winding coil sets
ACl"-AC4" comprises a plurality (e.g., six) of serially connected coils.
For example, coil set ACl" includes six serially connected coils
AC1a"-AC1f". The coils of winding W" are inserted in core 5" in layered
groupings generally in accordance with the above-mentioned, coassigned
U.S. Pat. No. 4,426,771.
Referring now to FIGS. 9-11A, three different connection patterns for the
twelve pole, four speed windings W", as heretofore described in regard to
FIGS. 7 and 8, are illustrated. Referring first to FIGS. 9 and 9A, it will
be seen that the auxiliary winding A" comprises four serially connected
coil sets ACl"-AC4" in series with permanent run capacitor C". A first
tapping point, as indicated at TP1", is provided between auxiliary winding
coil sets AC1" and AC2". A second tapping point TP2" is provided between
the second and third auxiliary coil sets AC2" and AC3", and a third
tapping point TP3" is provided between the third and the fourth auxiliary
coil sets AC3" and AC4". Still further, a fourth or last tapping point, as
indicated at TP4", is provided between the last auxiliary coil set AC4"
and main winding M". A multiple position, single throw, multiple pole
speed selector switch, as indicated at 33", is provided and is connected
to one of the power leads, as indicated at P2, of a source of AC
electrical power. Switch 33" has a selectively movable switch arm SA"
selectively movable to any one of a number of pole positions including an
off position in which the windings W" are de-energized to a high speed
position, to a first intermediate speed position, to a second or slower
intermediate speed position, and to a low speed position. Respective lead
wires L4", L3", L2" and Ll" connected the high, first intermediate, second
intermediate and low speed terminals of switch 33" to tap points TP4",
TP3", TP2" and TP1".
In FIG. 9A, each of the auxiliary winding coil sets ACl"-AC4" is shown to
each comprise six serially connected coils, as indicated by
AC1a"-AC1f"--AC4a"-AC4f', respectively. Furthermore, the first tapping
point TP1" is shown to comprise a connection between the first auxiliary
coil set AC1" and the second auxiliary coil set AC2' and the low speed
terminal of selector switch 33". The second tapping point TP2" is shown to
comprise a connection between both the second and third auxiliary coil
sets AC2" and AC3" and the second intermediate speed switch terminal of
selector switch 33". The third tapping point TP3" is shown to comprise a
connection between auxiliary coil sets AC3" and AC4" and the first
intermediate selector switch contacts. Likewise, the fourth or last
tapping position TP4" comprises an electrical connection between the
fourth auxiliary coil sets AC4" and the main winding and between the high
speed switch terminal of selector switch 33".
Thus, when switch arm SA" of switch 33" is moved from its off to its high
speed position (as shown in FIGS. 9 and 9A), AC electrical power from lead
P2 is supplied to the last tapping point TP4" thereby to connect all of
the coil sets ACl"-AC4" in series with each other and in series with
capacitor C" and so as to connect the capacitor and all of the coil sets
in parallel with main winding M" such that the motor operates at its high
speed mode of operation. When switch arm SA" is moved from its high speed
position to its first intermediate operation, AC power from lead P2 is
connected to tapping point TP3 such that only the first through the third
auxiliary coil sets ACl"-AC3" are energized in series with capacitor C"
and such that the first three coil sets are energized in series with both
main winding M" and with the fourth auxiliary coil set AC4" such that the
motor operates at its first or highest intermediate speed mode of
operation. When the switch arm SA" is moved to its second intermediate
position, AC electrical power from lead P2 is supplied to the second
tapping point TP2" such that only the first and second auxiliary coil sets
AC1" and AC2" are connected in series with capacitor C" and such that the
last two auxiliary coil sets AC3" and AC4" are connected in series with
main winding M" whereby the motor operates at a still slower intermediate
speed of operation. Lastly, when switch arm SA" is connected to its low
speed terminal, AC electrical power from lead P2 is supplied to the first
tapping point TP1" such that only the first auxiliary coil set ACl" is
connected in series with capacitor C" and such that the last three
auxiliary coil sets AC2"-AC4" are connected in series with main winding M"
whereby the motor operates at its slow speed mode of operation.
EXAMPLE
A K55 twelve pole PSC ceiling fan motor, such as is illustrated in FIG.
7-9A, was assembled in the manner heretofore described. The main winding
M" included 285 turns of No. 30 copper magnet wire and the auxiliary
winding A" included 284 turns of No. 30 copper magnet wire, having a total
magnet wire weight of about 1.0 pounds (454 grams). The value of capacitor
C" was six microfarads, 220 volts. When assembled in an overhead ceiling
fan motor configuration with the paddle fan blades in place on hub 23, the
motor was operated at four different operational speeds (i.e., high speed,
a first intermediate speed, a second intermediate speed, and a low speed).
The results of the tests for this motor showing selector switch position,
current draw (as expressed in amps), power consumed (expressed in watts),
and fan speed (expressed in RPM) are shown below in Table I.
TABLE I
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CURRENT
SPEED DRAW POWER CONSUMED SPEED
POSITION (AMPS) (WATTS) (RPM)
______________________________________
High .66 78 242
1st Intermed.
.50 56 185
2nd Intermed.
.37 38 123
Low .29 28 73
______________________________________
It will be understood that a comparable prior art motor, such as shown in
FIG. 12, would require substantially more magnet wire for its windings.
Referring now to FIGS. 10 and 10A, an alternative lead wire connection
pattern for windings W" inserted in stator core 5" in a manner generally
similar to that shown in FIG. 7 is illustrated. As best shown in FIG. 10,
the primary difference between the lead wire connection patterns between
FIG. 9 and FIG. 10 is that the fourth auxiliary coil set AC4" of FIG. 10
is not connected in series to main winding M" except when switch arm SA"
is in its high speed position. Still further, an on/off switch, as
generally indicated at 35, is provided in series with power lead P2 so as
to control energization and de-energization of windings W". With on/off
switch 35 closed, AC power is supplied to main winding M" and to the power
input terminal 37 speed selector switch 33" by a lead L5". With selector
switch arm SA" in its high speed mode of operation, all of the auxiliary
coil sets ACl"-AC4" are connected in series with one another and in series
with capacitor C", and further all of the auxiliary coil sets and the
capacitor are connected in parallel with main winding M" such that the
motor illustrated in FIG. 10 operates in much the same manner as the motor
illustrated in FIG. 9 in its high speed mode of operation. However, when
the selector switch SA" of the motor of FIG. 10 is moved from its high
speed position to its first intermediate speed position, to its second
intermediate speed position, or to its slow speed position, one or more of
the auxiliary coil sets AC4", AC3" and/or AC2" is removed from the
auxiliary winding circuit such that when AC power from lead P2 is supplied
to tapping points TPl"-TP3", the removed auxiliary coil sets are not
placed in series with main winding M", but rather are de-energized. It
will be appreciated that this is a different mode of operation than in the
voltage divider embodiment shown in FIGS. 9 and 9A which when one of the
slower speed modes of operation is utilized, one or more of the auxiliary
coil sets is connected in series with the main winding and thus
constitutes a portion of the main winding.
Referring now to FIGS. 11 and 11A, still another connection pattern for the
auxiliary winding A" is illustrated in which the speed selector switch, as
indicated at 33a", is shown to be a four position speed selector switch
(whereas the four speed selector switches 33" shown in FIGS. 9-10A was a
five position switch) and yet four different speeds of operation may yet
be controlled by means of the three speed selector switch 33a". More
specifically, in FIG. 11, it will be noted that tap points TPl"-TP4" are
generally similar to the tap points heretofore illustrated and described
in regard to FIG. 9 However, a separate on/off switch 35, such as
heretofore described in regard to FIG | | |
