Rotary line transfer switch

An improvement in oscillatory line transfer switches of the type having mechanical drive between a drive motor and the shafts of two such switches plus a manual mechanical switch to supplement the drive motor and having a third shaft mechanically connected into the same drive which controls a neutral position. An oscillatory switch system is used to switch from utility power sources to emergency power sources when the normal line supply is temporarily not available. This condition is sensed, an emergency generator activated, and, when the latter is up to needed voltage, the line transfer switches are thrown. After normal line voltage is restored, the switches oscillate back to normal power sources. A gear train causes at least two switches to turn simultaneously.

This invention relates to a new and improved rotary line transfer switch. 
Reference is made to U.S. Pat. No. 3,796,937 on which the present 
invention is an improvement. A rotary switch system is used to switch from 
utility power sources to emergency power sources when the normal line 
supply is temporarily not available, either because of a decrease in line 
voltage or in frequency. The equipment senses when any one of the phases 
of the normal line voltage drops below a pre-selected percentage of 
normal. Thereupon a generator for auxiliary power is activated and, when 
this has been brought up to the needed voltage, the present invention 
provides a means to throw the line transfer control switch from normal 
line position to emergency line position. After normal line voltage has 
been restored, the switch transfers back to normal power source. 
As disclosed in the aforesaid patent, a motor is turned by the sensing 
means, thereby turning a shaft. Turning of the motor turns a switch 
actuating lever which rotates the shafts of the line transfer switches. 
Manual override of the motor is also provided. 
In accordance with the present invention, the motor causes oscillatory 
movement of the shaft of the first line transfer switch. By means of a 
gear train, the shaft of the second line transfer switch is simultaneously 
turned. 
In accordance with the present invention, a handle is connected to the 
shaft of one of the rotary switches and by means explained in U.S. Pat. 
No. 3,796,937, when the operator wishes to override the drive motor, the 
handle may be turned to accomplish that result. Provision is made in 
accordance with the present invention to interlock the two switches so 
that it is impossible that both switches be closed at the same time, a 
situation which would burn out the switches. The arrangement is such that 
one switch must be opened before the other can be closed. On the other 
hand, a neutral switch is of a type which makes contact before breaking 
the previous contact. 
A further improvement of the present invention is the provision of an 
off-on switch for the drive motor to inactivate the same. 
A still further feature of the invention is the provision of a brake on the 
motor to prevent overrun. 
Other objects of the present invention will become apparent upon reading 
the following specification and referring to the accompanying drawings in 
which similar characters of reference represent corresponding parts in 
each of the several views.

As has been stated, many of the elements of the present device are similar 
to those shown in U.S. Pat. No. 3,796,937 and, hence, reference is made 
thereto for explanation of some of the similar elements. The casing 11 
surrounds and encloses two rotary line transfer switches 10. A preferred 
switch 10 is manufactured by Klockner-Moeller and is known as N11-400-CNA. 
The casings for such switches 10 are preferably of a molded clear plastic 
so that the mechanisms are visible and it is possible to determine whether 
the contacts are open or closed. Nine terminals for connection to 
three-phase lines are provided and are mounted on the casing 11. Thus 
terminals 12a,b,c are for the three phases of the normal power source, 
usually a utility power line. Terminals 13,a,b,c are for the emergency 
power source, usually an engine-generator set frequently used in 
hospitals, commercial and industrial buildings where outages of utility 
power may have serious consequences. Terminals 14,a,b,c are for connection 
to the load. Busses 16a,b,c connect the corresponding output terminals of 
the two switches 10. Hence, regardless of whether normal power or 
emergency power is being provided at a given instant, the load 14a,b,c is 
properly connected. 
Shaft 21 extends up through the top of the emergency power casing 10 and 
shaft 22 extends up from the normal switch casing (left hand side of FIGS. 
1 and 2). By internal mechanism, not herein illustrated, provided by the 
manufacturer of the switches 10, when the shaft 21 or 22 is turned, the 
rotary switches for all three phases are turned simultaneously. 
An interlock is provided to insure that, at no time, are both of the 
switches 10 closed. The interlock assures that, before either of the 
switches 10 may be closed, one of the switches must be opened. Such 
interlock is manufactured by Klockner-Moeller and is designated by Catalog 
No. KV-2NZM11. For interlock purposes, a non-circular bottom extension 23 
of shaft 21 and a non-circular bottom extension 24 of shaft 22 are each 
provided with cams 26,27 having low dwells as shown in FIG. 3. Mounted 
below the casing 11 between the shafts 23,24 is a connector 28 having 
depending therefrom guides 29 for a horizontally reciprocating slide 31. 
The enlarged heads of the guides 29 restrain the slide 31 to movement 
parallel to the connector 28. At either end of the slide 31 is a pointed 
cam follower 32 which engages one or the other or neither of the cams 
26,27. The distance between the points 32 with reference to the shapes of 
the cams 27 is such that at no time can both switches 10 be closed, but 
one of the switches must be open before the other can be closed. 
Horizontal base 36 is fixed to the top of casing 11 and provides for a 
mounting for various gears hereinafter described, all of which are 
provided with bearings 43. Gear 37 is mounted on shaft 22. A pair of 
direction changing idlers 38 are mounted on base 36, but are not connected 
to switches 10. Gear 39 is mounted on shaft 21. The dimensions of the 
gears 37,38,39 are such that the shafts 21,22 turn equi-angularly. Another 
idler 41 is mounted on base 36 and engages gear 39 and also meshes with 
gear 42. Gear 42 is mounted on the shaft of rotary switch 44 which may be 
a cam switch such as Klockner-Moeller switch T44/ez-60-7-NA. 
Switch 44 is used with 3-phase, 4-wire power. Normal power neutral is 
connected to terminal 12d; emergency power neutral is connected to 
terminal 13d; the load neutral is connected to terminal 14d. Switch 44 
closes its contacts from the alternate source (e.g. 13d) before opening 
its contacts from the previous source (e.g. 12d). This prevents momentary 
opening of the neutral which could otherwise cause high voltage to be 
applied to low voltage loads, thereby damaging these devices. 
On the left side of casing 11, as viewed in FIGS. 1 and 2, is a motor 46 
suitably geared down and provided with a brake 47 so that it turns only 
one revolution per cycle. The shaft 48 of the motor extends upward and has 
fixed thereto a crank 49. Loose on shaft 48 is bottom arm 51 below crank 
49 and upper arm 52 above crank 49. Bolt 53 passes through threaded holes 
in the outer ends of arms 51,52 but does not pass through the crank 49. 
The connecting rod 54 carries, at its left end, end piece 56 which is 
apertured to receive bolt 53. End piece 57, at the opposite end of rod 54, 
is likewise provided. End pieces 56 and 57 and the opposite ends of rod 54 
are oppositely threaded so as to adjust the over-all length of the rod 54 
by twisting same. As motor 46 turns, it contacts upward extension 58 of 
arm 51 and causes the arms 51,52 to pivot about shaft 48 and, accordingly, 
to cause movement of rod 54. Fixed to shaft 22 and extending radially 
therefrom is a crank 61 carrying a pin 62 at its outer end which is 
received in end piece 57. A snap pin 63 passes through a diametric hole in 
pin 62. By removing the pin 63, the end piece 57 may be disconnected from 
pin 62 when required. Handle 64 also extends radially outwardly from and 
is fixed to shaft 22. The relationship of crank 49 relative to the arms 
51,52 is such that when required, an attendant may shift the handle 64 
manually through about 60.degree. of travel and cause the shafts 21,22 to 
turn accordingly independently of the motor 46. On the other hand, when 
the motor 46 is again energized, the crank 49 again contacts the extension 
58 and turns the shaft 22 through 60.degree., all as explained in U.S. 
Pat. No. 3,796,937. 
Although the motor shaft 48 is illustrated in the drawings and described 
herein as connected to shaft 22, it will be understood that it could be 
connected to shaft 21. 
As is clear from consideration of FIG. 1, when the motor 46 turns through 
one revolution, the crank 61 is moved in a counterclockwise direction 
60.degree.. The next time the motor 46 is energized, the crank 61 is moved 
in the opposite direction 60.degree.. Such movement of crank 61 is 
transmitted both to shafts 22 and 21, as well as to the shaft of rotary 
switch 44. Alternatively, an attendant may shift the handle 64 through 
60.degree. of travel independently of motor 64. Nevertheless, when the 
motor 46 is again energized, the crank 61 is again shifted 60.degree.. In 
emergency situations, by removing the pin 63 and disengaging the end piece 
47 from the pin 62, purely manual switching may be acccomplished through 
the handle 64. 
As a protection against injury of personnel, a cover 66 having depending 
legs 67 fixed to the base 36 extends above the gears 37-42. The cover 36 
may be held down also by extensions 68 of the shafts of idler gears 38 
which protrude through holes in cover 66 and carry nuts 69. 
Directing attention now to the wiring diagram of FIG. 4, the load terminals 
14a-c may be connected either to the normal power supply terminals 12a-c 
or the emergency power terminals 13a-c depending upon the position of the 
lever 61 (not shown in FIG. 4 but readily understood). When normal power 
is carrying the load, it passes through contacts M1 and is also sensed by 
voltage sensitive relay VSR via transformers T1 and T2. VSR closes its 
contacts to complete a circuit to TD1, TD2 and TD3. Indicator lamp R is 
illuminated. Time delay relay TD1 is timed on dropout and picks up to open 
the circuit between the terminals 76, causing the engine-generator set to 
stop and hence stopping supply of power to terminals 13a-c. 
Time delay relays TD2 and TD3 time out, transferring their contacts to 
deenergize their drive motor 77,78, respectively, but leaving their clutch 
coils 79 energized. Although not illustrated in FIG. 4, motors 77 and 78 
have coils which cause the contacts of TD.sub.2 and TD.sub.3 to be changed 
in well known manner. 
If, for some reason, power supply should fail either in a single phase or 
in entirety or drop below 70% of voltage, VSR senses such condition, 
opening its contacts and deenergizing coils TD1, TD2, TD3 and control 
relay CR1. All of these drop out, except TD1 which commences timing and 
when timed out, closes its contacts to short out terminals 76. This sends 
a start signal to the engine-generator set. 
If normal power is restored before the timing out of time delay TD1 is 
complete, TD1 will stop timing and will reset back to its maximum time 
point and the start signal to the engine-generator set will not be 
initiated. Hence, the standby system ignores very short duration power 
outages. 
If normal power is out long enough (a time interval which is variable but 
is preferably about 21/2 seconds) to allow TD1 to complete its timing, the 
standby engine generator will be started and when its output reaches 80% 
nominal voltage, such condition will be sensed by frequency sensitive 
relay FSR and transformer T3. When the frequency reaches a set point (e.g. 
57.5 cycles for a normal 60 cycle system or 48 cycles of a normal 50 cycle 
system) relay FSR contacts are closed and coils CR2 and CR3 are energized. 
CR3 operates to remove time delay bypass in the normal power control. CR2 
closes its contacts to complete the circuit to the drive motor 46 via CR1. 
Normally closed contacts LS2 contacts and disconnect switch 81. Switch 81 
is a manual switch located on the casing 11 and is normally closed, but 
may be opened manually when the control system is to be disconnected. 
When drive motor 46 is energized, it opens main contacts M.sub.1 and when 
they are open closes main contacts M2 allowing the standby power to supply 
the load. When the drive motor 46 completes one cycle of its operation, it 
transfers contacts of LS1 and LS2 and the indicator light G is now lighted 
through switch LS2. 
When normal power is again restored, it is sensed by relay VSR which closes 
its contacts, energizing timer TD2. Timer TD3, TD1 and relay CR1 are not 
energized because relay CR3 is now operated and its contacts are opened. 
TD2 commences timing and when completed transfers its contacts to 
deenergize its drive motor 77 and energize coil CR1 and timer TD3. Relay 
CR1 operates, opening its contacts in series with switch LS2 to extinguish 
lamp G and prevent a retransfer and closing its contacts in series with 
LS1 to energize the drive motor 46. Drive motor 46 operates to open main 
contacts M1, connecting the load to normal power supply and again 
transfers contacts LS2 and LS1. Lamp R is again lighted. Timer TD3 now 
commences timing and when it times out causes its contacts to transfer, 
deenergizing motor 78 and energizing timer TD1. Timer TD1 operates, 
opening its contacts to remove the short between the terminals 76 which 
causes the engine generator set to stop. When the engine slows to lower 
speed, relay FSR drops out, deenergizing relays CR2 and CR3. These relays, 
in turn, will drop out and contacts will be in initial positions. 
If normal power is available and the generator is carrying its load but the 
generator should fail, relay CR3 will drop out, closing its contacts, 
bypassing TD2 and TD3. Relay CR1 will then pull in and cause the transfer 
switches 10 to connect the load to normal power source. 
The test switch TS shown in FIG. 4 is a 3-positioned switch having "LT 
Test", "Normal" and "Engine Test" positions. When it is placed in "Engine 
Test" position its contacts 72 close to short out terminal 76. The engine 
starts and operates, but no transfer takes place unless the normal power 
source should fail. When switch TS is in "LT Test" position, contacts 73 
are opened. This causes TD.sub.1, TD.sub.2, TD.sub.3 and CR.sub.1 to be 
de-energized, thus simulating a power failure. The Transfer switch then 
starts the engine and transfers the load to the generator as previously 
explained. The transfer switch can be operated manually by turning 
disconnect switch 81 to off position, removing the snap pin 63, removing 
the end piece 57 from the pin 62 and throwing the handle 64 to opposite 
direction. 
The switch can be arranged to operate on a desired voltage by reconnecting 
the sensing transformers and adjustng the relay VSR to desired level. 
Further, the switch FSR will operate on any cycle by proper adjustment of 
relay FSR. 
FIG. 4 also shows the wiring for switch 44, which switches with switches M1 
and M2. The neutral fourth wires of the normal and emergency power source 
are wired to contacts 12d and 13d and the neutral load to 14d. The 
structure of switch 44 is such that it must establish contact of 14d with 
either 12d or 13d before it opens contact with either of the latter.