US 8,134,437 B2
`(10) Patent No.:
`az) United States Patent
`Brooks
`(45) Date of Patent:
`Mar.13, 2012
`
`
`US008134437B2
`
`(54) EDDY CURRENT INDUCTIVE DRIVE
`ELECTROMECHANICALLINEAR
`ACTUATOR AND SWITCHING
`ARRANGEMENT
`
`(75)
`
`Inventor: Elliot Brooks, Foothill Ranch, CA (US)
`
`3/1935 Rhine
`1,993,946 A
`ties plompson
`saeco,
`11/1949 Sonnemann
`3488443 A
`9/1961 Gendreu
`3,001,115 A
`12/1964 Schreiber
`3,162,796 A
`3/1965 Fulton
`3,176,170 A
`12/1968 Lace
`3,417,268 A
`4/1970 Helms
`3,505,544 A
`(73) Assignee: PowerPath Technologies LLC, San
`6/1971 Yoshimura
`3,585,458 A
`y
`Capist
`CA (US
`
`uan Capistrano,CA(US) 3,599,020 A 8/1971. Harris
`
`3,619,673 A
`11/1971 Helms
`(*) Notice:
`Subject to any disclaimer, the term ofthis
`(Continued)
`patent is extended or adjusted under 35
`USC. 154(b)by 142 days.
`FOREIGN PATENT DOCUMENTS
`11/920,785
`9 364 308
`4/1990
`(Continued)
`
`(21) Appl. No.:
`
`EP
`
`(22) PCT Filed:
`
`May 20, 2006
`
`(86) PCT No.:
`$371 (Q)
`OE);
`(2), (4) Date: Mar. 2, 2009
`
`PCT/US2006/019779
`
`(87) PCT Pub. No.: WO2006/127628
`PCT Pub. Date: Nov. 30, 2006
`
`(65)
`
`Prior Publication Data
`US 2009/0212889 Al
`Aug. 27, 2009
`
`(51)
`
`Int. Cl.
`(2006.01)
`HOLF 7/08
`(52) U.S. CL......... 335/222; 335/100; 335/147; eae’
`.
`.
`.
`;
`(58) Field of Classification Search .................. 335/100,
`file f awenae 245
`S
`lication
`ee appication
`Mile
`tor complete search
`Astory.
`References Cited
`U.S. PATENT DOCUMENTS
`
`(56)
`
`1,384,769 A
`1,711,285 A
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`
`7/1921 MacLaren
`4/1929 Petersen
`4/1934 Pridhan
`
`OTHER PUBLICATIONS
`a
`Low Voltage
`leve,
`ectromagnetic
`veter,
`Low
`Z
`Voltage Elect:
`gnetic
`Riveter,
`Oct. 21, 1986.
`
`ectroimpact,
`Electroimpact,
`
`ine.,
`
`I
`
`(Continued)
`
`Primary Examiner — RamonBarrera
`(74) Attorney, Agent, or Firm — D. Stein
`
`ABSTRACT
`(57)
`The present invention is directed to an inductively driven
`ar
`:
`electromagneticlinear actuator arrangement employing eddy
`currents induced by a fixed drive coil to drive its armature
`Eddy current focusing fields are employed to direct the eddy
`currents using Lorentz forces to maximize armature speed.
`The armatureincludesa shorted driven coil ina DC magnetic
`field. This can be supplied by a permanent magnet. When
`current is applied, a force is felt by the coil in a direction
`perpendicular to the magnetic field. Such an actuator is well
`suited for electrical switching applications including transfer
`switching applications, circuit breaker applications, and
`groundfault interrupter applications.
`
`28 Claims, 20 Drawing Sheets
`
`APPLE 1031
`
`APPLE 1031
`
`1
`
`

`

`US 8,134,437 B2
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`Page 2
`
`U.S. PATENT DOCUMENTS
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`Studtmann
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`Gillum
`Sato
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`Hughes
`TN9TS
`Chari
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`Corey
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`Adler
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`Jencks
`Hunt
`10/1978
`8/1979
`Jencks
`9/1979
`Wiktor
`Hurst
`7/1980
`11/1980
`Kruger
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`Lienau
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`Hathaway
`3/1982
`Munehiro
`Farmer
`11/1983
`Iverson
`12/1983
`3/1984
`Brende
`6/1984
`Symonds
`Lee
`10/1984
`11/1984
`Cheffer
`Stout
`2/1985
`2/1986
`Gibeau
`4/1986
`Kordik
`7/1986
`Griffith
`7/1986
`Van Davelaar
`11/1986
`Weldon
`12/1986
`Viskochil
`3/1987
`Wilcox
`Hames
`4/1987
`Ito
`5/1987
`Scranton
`5/1987
`9/1987
`Frandsen
`Luoma
`10/1987
`11/1987
`Gephart
`12/1987
`Karidis
`1/1988
`Powell
`2/1988
`Snyder
`DeKoster
`4/1988
`TN988
`Itagaki
`11/1988
`Baker
`1/1989
`Richeson, Jr.
`1/1989
`Suzuki
`2/1989
`Dreibelbis
`2/1989
`Godkin
`Lutz
`8/1989
`11/1989
`Mawla
`12/1989
`Van Niekerk
`3/1990
`Richeson, Jr.
`‘Yumura
`3/1990
`8/1990
`Erd.
`10/1990
`Elieli
`1/1991
`Irwin
`2/1991
`Kemeny
`5/1991
`Shtipelman
`6/1991
`Sugiyama
`TN991
`Hatchett
`10/1991
`Sneddon
`10/1991
`Nashiki
`12/1991
`Castenschiold
`1/1992
`Smith
`1/1992
`Narasaki
`Hammer
`3/1992
`8/1992
`Horikoshi
`Hearm
`9/1992
`Prescott
`11/1992
`1/1993
`Sim
`1/1993
`Woodworth
`4/1993
`Sim
`Rosa
`5/1993
`Prescott
`11/1993
`5/1995
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`
`3,634,701
`3,656,015
`3,666,977
`3,715,694
`3,723,779
`3,723,780
`3,783,311
`3,852,627
`3,889,139
`3,896,319
`3,932,764
`4,075,517
`4,087,773
`4,121,124
`4,166,262
`4,168,407
`4,210,831
`4,233,481
`4,287,445
`4,295,011
`4,318,038
`4,414,594
`4,423,336
`4,439,699
`4,455,555
`4,475,066
`4,484,084
`4,498,023
`4,573,094
`4,584,495
`4,599,668
`4,603,270
`4,621,561
`4,631,431
`4,652,779
`4,661,729
`4,665,947
`4,669,013
`4,692,999
`4,700,246
`4,709,318
`4,712,027
`4,719,550
`4,725,801
`4,739,292
`4,758,750
`4,782,241
`4,794,890
`4,795,928
`4,808,892
`4,808,955
`4,853,808
`4,882,508
`4,884,954
`4,908,731
`4,910,486
`4,951,023
`4,965,839
`4,988,907
`4,993,311
`5,016,238
`5,023,581
`5,029,029
`5,053,660
`5,055,760
`5,070,252
`5,081,367
`5,081,381
`5,093,596
`5,142,172
`5,146,122
`5,159,949
`5,177,383
`5,182,464
`5,202,595
`5,210,685
`5,257,639
`5,420,468
`
`
`
`PPPrPPEEPLESPEESEPPEEEESEEESEPSPEEEEEESEEESPPEPEESEEEEPEEPPEPEPSEPEPPeerPPrPS
`
`7/1995 Stuart
`5,434,458 A
`8/1995 Denne
`5,440,183 A
`6/1996 Boys
`5,528,113 A
`11/1996 Kunert
`5,576,604 A
`2/1997 Walton
`5,602,930 A
`5/1997 Stephany
`5,631,505 A
`6/1997 Sharaf
`5,638,948 A
`7/1997 Galm
`5,644,175 A
`12/1997 Mody
`5,694,098 A
`12/1997 Brand
`5,694,312 A
`12/1997 Dunfield
`5,698,911 A
`12/1997 Orlowska
`5,701,040 A
`2/1998 Varian
`5,717,552 A
`3/1998 McGrath
`5,727,932 A
`3/1998 Hallidy
`5,734,209 A
`5/1998 Przywozny
`5,748,432 A
`7/1998 Weber
`5,780,990 A
`9/1998 Zhao
`5,808,379 A
`9/1998 Bandera oo... cece 310/14
`5,814,907 A *
`1/1999 Steingroever
`5,864,274 A
`5/1999 Elenbaas
`5,903,203 A
`6/1999 Jonas
`5,914,467 A
`7/1999 Smith
`5,920,129 A
`1/2000 Hannagan
`6,015,273 A
`2/2000 Oudet
`6,028,499 A
`8/2000 Morroni
`6,100,604 A
`8/2000 Zajkowski
`6,100,605 A
`10/2000 Chitayat
`6,137,195 A
`1/2001 Tsuzuki
`6,176,208 Bl
`3/2001 Seale
`6,208,497 BI
`6/2001 Heo
`6,252,315 Bl
`10/2001 Hayes
`6,297,640 Bl
`11/2001 Sutrina
`6,312,434 Bl
`12/2001 Guenther
`6,326,710 Bl
`3/2002 Davey
`6,357,359 BI
`4/2002 Calhoon
`6,365,993 BI
`6/2002 Inami
`6,409,144 Bl
`9/2002 Marder
`6,445,092 BI
`11/2002 Reynolds
`6,483,682 Bl
`4/2003 Daun-Lindberg
`6,542,023 Bl
`5/2003 Rajda
`6,560,128 Bl
`6/2003 Turner
`6,577,216 B2
`7/2003 Turner
`6,590,481 B2
`7/2003 Anderson
`6,593,670 B2
`8/2003 Hollingsworth
`6,603,224 Bl
`8/2003 Denne
`6,608,408 BI
`8/2003 Durham
`6,611,078 BI
`9/2003 Allison
`6,624,720 Bl
`10/2003 van Namen
`6,639,496 BI
`10/2003 Inoguchi
`6,639,759 B2
`12/2003 Yeo
`6,664,663 Bl
`3/2004 Blair
`6,700,351 B2
`4/2004 Denne
`6,721,641 Bl
`6/2004 Ehrhart
`6,750,576 B2
`7/2004 Rademacher
`6,765,157 B2
`7/2004 Powell
`6,768,223 B2
`8/2004 Denne
`6,770,988 B2
`6,836,201 B1* 12/2004 Devenyietal. ow... 335/229
`6,879,060 B2
`4/2005 Hohri
`6,917,124 B2
`7/2005 Shetler, Jr.
`2002/0080531 Al
`6/2002 Inoguchi
`FOREIGN PATENT DOCUMENTS
`545712
`6/1942
`
`GB
`
`OTHER PUBLICATIONS
`
`Zieve at al., High Force Density Eddy Current Driven Actuator,
`Electroimpact, Inc., 1988.
`Zieve etal., Advanced EMRTechnology, Electroimpact, Inc. Oct. 13,
`1992.
`Hartmann, Development of the Handheld Low Voltage Electromag-
`netic Riveter, Electroimpact, Inc. Oct. 30, 1990.
`Hartmann et al., Low Voltage Electromagnetic Lockboft Installation,
`Electroimpact, Inc., Oct. 13, 1992.
`DeVlieg, Lightweight Handheld EMRwith Spring-Damper Handle,
`Electroimpact, Inc. Sep. 20, 2000.
`
`* cited by examiner
`
`2
`
`

`

`U.S. Patent
`
`Mar. 13, 2012
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`Sheet 1 of 20
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`Fig. 1 (Prior Art)
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`56
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`\ ae
`
`se
`
`38
`
`Load
`
`(2
`
`yO
`
`60
`
`81
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`$2
`
`
`
`
`3
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`

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`U.S. Patent
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`US 8,134,437 B2
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`>}
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`146498
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`160
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`80
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`136
`142
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`122°
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`116
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`4
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`g4' 192
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`5
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`190
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`cc
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`94!
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`190
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`/
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`6
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`™. P
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`Mechanical
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`_ Motion
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`7
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`Sheet 6 of 20
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`170
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`Load
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`Output
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`8
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`224
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`80'
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`222
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`ele
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`216
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`224
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`9
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`222
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`210
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`214
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`Fig. 10
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`10
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`10
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`Sheet 9 of 20
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`11
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`Sheet 10 of 20
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`US 8,134,437 B2
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`230
`Tinte
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`Yeail
`
`+Veug
`
`248
`
`Veull
`
`242
`
`Time
`
`Orive: From Down to Up
`
`Drive: From Up to Down
`
`Fig. 13
`
`Fig. 14
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`12
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`12
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`

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`U.S. Patent
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`Mar.13, 2012
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`Sheet 11 of 20
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`US 8,134,437 B2
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`Voltage
`
`Voltage
`
`Gate Drives: From Dawn to Up
`
`Gate Orives: From Up to Gown
`
`Fig. 15
`
`Fig. 16
`
`258
`
`
`
`
`
`
`
`
`
`
`
`
`Controller L
`
`
`
`Up/Down
`
`Micro-
`
`
`
`
`
`
`PositionSensor
`
`LOare
`Fig. 17
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`230
`
`va
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`262
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`13
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`13
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`14
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`14
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`Sheet13 of 20
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`US 8,134,437 B2
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`a
`
`= ayTHe a
`
`Load
`NCANNdil
`Fig. 21
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`15
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`fey a 36
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`Active | Snubber
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`100
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`
`
`
`
`Output
`Load
`
`
`
`
`
`(momentary)
`
`
`
`Contra) Up/Down|Relay |
`320——>
`
`
`Driver
`
`
`
`.
`
`Alarm
`
`18
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`18
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`20
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`Sheet19 of 20
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`US 8,134,437 B2
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`
`
`
`3-Posiion
`Transfer
`Switch
`
`(St - OF- 825
`
`é-Posiion
`
`Transfer
`Suwitch
`
`(St - Of - 825
`
`
`
`$- Position
`Transfer
`Suvitch
`
`(81 - Of- 82)
`
`é-Position
`Transfer
`Switch
`
`(81 - Of - $2)
`
`Load
`
`Loeel
`
`Load
`
`Load
`
`Fig. 28
`
`21
`
`21
`
`

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`U.S. Patent
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`Mar. 13, 2012
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`Sheet 20 of 20
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`US 8,134,437 B2
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`I
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`52
`
`Electronically Open/Close
`Gircuit Breaker
`
`Redurcant Network
`
`Connection
`
`Electronically Open/Close
`Circuit Breaker
`
`
`
`
`
`
`Electronically Open/Glase
`Circuit Breaker
`
`
` Redundant Metuork
`|
`’
`342
`Gannecton
`
`
`
` Electronically Open/Close
`340 —-————- |
`Circuit Breaker
` Redundant Hetuark
`
`Connection
`
`
`342
`
`Load
`
`Load
`
`22
`
`22
`
`

`

`US 8,134,437 B2
`
`1
`EDDY CURRENT INDUCTIVE DRIVE
`ELECTROMECHANICAL LINEAR
`ACTUATOR AND SWITCHING
`ARRANGEMENT
`
`CROSS REFERENCE TO RELATED
`APPLICATION
`
`This application claimsall benefits of and priority under 35
`USS.C. Section 119(e) to U.S. Provisional Application Ser.
`No. 60/573,172, filed May 20, 2004, the entirety of which is
`hereby expressly incorporated herein by reference.
`
`FIELD OF THE INVENTION
`
`The present invention is directed to an actuator, switch, and
`relay, and more particularly to an electromechanical linear
`actuator capable of high speed actuation and a switch actu-
`ated thereby capable of power switching equipment use in
`fuses, breakers, ground fault
`interrupters, uninterruptible
`powersupplies, distributed power switches, automatic trans-
`fer switches andstatic transfer switches.
`
`BACKGROUNDOF THE INVENTION
`
`There are manytypesofelectrical switches that have been
`used in the past for switching electrical current. In its most
`simplest form, a switch has twoelectrically conductive con-
`tacts that touch each other to allow electrical current to flow
`
`througha circuit, “making”the circuit, and that are separated
`whenit is desired to prevent current from flowing through the
`circuit, “breaking” the circuit. Another type of switch com-
`monly used is a semiconductor switch, which is of non-
`mechanical construction and typically employs one or more
`transistors or thelike.
`
`Some types ofmechanical switches are manually actuated.
`Examples of manually actuated switches
`include,
`for
`example,
`light
`switches, push-button switches,
`toggle
`switches,
`rocker
`switches, and rotary switches. These
`switches are manually actuated because they require a person
`to manually engage them, such as by using one or more
`fingers to press, turn or otherwise movethe switchto a desired
`position.
`Other types of mechanical switches employ an actuator
`that is used to move a switch to a desired position, such as to
`turn it on or off. A switch actuator is a device that transforms
`somesort of an input into motion that moves the switch to the
`desired position. Operation of a switch actuatoris typically
`controlled in somesort of automated manner. For example, a
`sensor, such as a voltage sensor, a current sensor, a tempera-
`ture sensoror another kind of a sensoror sensor arrangement
`can be used to provide an inputto the actuatorthat causesit to
`move a switch to a desired position.
`Not only can such switches be used to turn poweronoroff,
`they can also be employed to switch between two or more
`different inputs or sources, including, among other things,
`powersources. A switch used to switch between twodifferent
`inputs is called a transfer switch. Transfer switches are most
`commonly used to switch an electrical load between two
`different input power sources. Like virtually all types of
`switches, transfer switches can be of mechanical or semicon-
`ductor construction and can be manually actuated or auto-
`matically actuated. Automatically actuated mechanical trans-
`fer switches employ an actuator to movethetransfer switch to
`the desired position.
`Manual transfer switches are usually mechanical and are
`used to manually switch between two different inputs or
`
`15
`
`25
`
`35
`
`40
`
`45
`
`65
`
`2
`sources. In electrical power switching applications, they are
`used to switch an electrical load between two or more input
`sources of electrical power.
`One type of transfer switch, such as typically used for
`whole house power switching of powerfrom utility powerto
`generator power,
`is configured to provide a break-before-
`make or open transition switching arrangement. The term
`“break-before-make” means that the transfer switch first
`breaks the electrical connection with one sourceof electrical
`
`powerbefore makingthe electrical connection with the other
`sourceof electrical power. For example, when switching over
`to generator power, the transfer switch breaks the utility
`power connection before making the generator connection to
`prevent unwanted and potentially damaging power back-
`feed.
`A second type of transfer switch, often referred to as a
`“make-before-break”or closed transition transfer switch, is
`used in applications where it is desired to make the connec-
`tion with the second input before breaking the connection
`with thefirst input. In power switching applications, a “make-
`before-break” power transfer switch allows a hot-to-hot
`transfer withoutlossof critical load. To put it a different way,
`a “make-before-break” transfer switch permits switching
`between active or “hot” input sources.
`A third type of transfer switch is typically referred to as a
`center off or delayedtransition transfer switch. Delayed tran-
`sition transfer switchesare nearly always used in applications
`involving large inductive loads that can undesirably cause
`large inrush currents. In a delayed transition transfer switch,
`there is an intentional time delay between the breaking of the
`connection with thefirst input before making the connection
`with the second input. A time delay after breaking thefirst
`connection is provided sufficient to permit magneticfields of
`the inductive load to completely collapse before making the
`second connection.
`
`Mechanical transfer switches can employ an electrome-
`chanical actuator, such as a solenoid actuator, to move the
`transfer switch to the desired position. Whenit is desired to
`change transfer switch position, an input, in the form of
`electrical current, is applied to the actuator, or removed from
`the actuator, to cause an armature of the actuator to move ina
`desired direction as well as in at least some instances, to a
`desired position. Because the armature is connected or oth-
`erwise mechanically linked to the switch, movementof the
`armature also causes the switch to move. Therefore, con-
`trolled application of electrical current to the actuator causes
`its armature to move in a desired direction, typically to a
`desired position, causing the switch to move along with it to
`the desired switching position.
`FIG. 1 depicts an exemplary prior art solenoid actuator 40
`like that commonly used in electromechanical
`transfer
`switches. The solenoid 40 includesa stationary stator 42 that
`has a fixed electrical coil 44 around a center pole 46 of the
`stator 42 that is energized to urge an armature 48 made of
`magnetic material towardit in the mannerdepicted in FIG.1.
`Although not shownin FIG.1, a spring is used to return the
`armature 48 back to where it was originally located before
`energization of the coil 44. Unfortunately, dueat least in part
`to its relatively high inertia armature construction, solenoid
`actuators 40 have undesirably slow response times, which
`limits switching speeds andtransfer times whenusedin elec-
`tromechanical transfer switches.
`Another commonly used electromechanical actuator used
`in electromechanical transfer switches is a rotary or stepper
`motor-type electromechanical actuator. However, these elec-
`tromechanicaltransfer switch actuators do nothing to remedy
`the deficiencies found in the aforementioned solenoid actua-
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`US 8,134,437 B2
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`Thyristors or SCRsare typically used in solid state transfer
`tors. In fact, these types of actuators are often part of a rela-
`switches because they are more robust, have lower power
`tively complex transfer switch mechanism that
`includes
`losses, and can be used with simpler low-power control
`cams, gears, linkages andthe like. Not only are suchtransfer
`arrangements than other types of semiconductor switches.
`switch mechanisms unacceptably slow for more demanding
`SCRsare particularly well suited for high power switching
`transfer switch applications, their components can undesir-
`applications becauseoftheir ability to switch electrical cur-
`ably wear over time or evenstick, if not frequently tested,
`rents ranging from a few amps up to a few thousand amps,
`resulting in premature or even unexpected failure.
`which can amountto millions of watts in some powerswitch-
`Where a transfer switch is automatically controlled, it is
`ing applications.
`commonlyreferred to as an automatic transfer switch or ATS.
`Electromechanical automatic transfer switches utilize an
`Unfortunately, SCRs have certain disadvantages. For
`example, SCRsdissipate more power than electromechani-
`electromagnetic actuator, such as an aforementionedsolenoid
`cally actuated transfer switches sometimes producing a sig-
`or rotary or stepper motor actuator. Solid state automatic
`transfer switches, as discussed in more detail below, utilize
`nificant amount ofheat during operation. Asa result, cost and
`complexity is often increased as additional equipment may be
`semiconductor switching technology andare usedin transfer
`needed to removethe heat produced by the SCRs. Whereheat
`switching applications where fast switching is required.
`transfer equipment is needed, transfer switch maintenance
`While transfer switches that employ an electromagnetic
`and monitoring costs typically are undesirably increased.
`actuator have enjoyed substantial commercial
`success,
`Another drawbacklies in the fact that SCRs always require
`improvements nonetheless remain desirable. For example,
`a supply of control power to maintain connection between an
`conventional solenoid actuators and rotary stepper motor
`input source and the load. Should the control powerto the
`actuators in the past have been inherently slow operating,
`transfer switch fail, all of the SCRs will switch off, breaking
`limiting their use to switching applications tolerant of their
`each and every connection between input and load. To prevent
`slow switching speeds and slow transfer times.
`With specific regard to automatic transfer switching appli-
`this from happening,solid state transfer switches are usually
`
`cations,it has beenachallenge to achieve transfertimesfaster equipped with redundant power supplies. Unfortunately, the
`25
`than about seven alternating current cycles, e.g., less than 120
`level of redundancy typically required to ensure reliable and
`milliseconds where sixty hertz alternating current is used,
`stable operation undesirably increases its purchase price,
`using a transfer switch that is electromagnetically actuated.
`adds to complexity, and requires additional monitoring and
`Indeed, it has been believed heretofore unknown to achieve
`maintenance,all of which is undesirable and addsto overall
`transfer times faster than two cycles, e.g., less than 33.3
`operational costs.
`A still further drawback lies in the fact that an SCR cannot
`milliseconds where sixty hertz alternating currentis used, in
`an automatic transfer switchthat is electromagnetically actu-
`ated. As a result, electromagnetically actuated automatic
`transfer switches have been limited to less critical switching
`applications, such as those where the load can tolerate up to
`five cycles of powerloss during switching.
`Where faster transfer or switching times are required,
`semiconductororsolid state transfer switches are used. These
`are used for more critical transfer switching applications,
`including those where the load cannottolerate loss of power
`for very long during switching. Semiconductor automatic
`transfer switches have been commercially available for quite
`some time that provide sub-cycle transfer times, thereby
`enabling switching to be performedin 1 7millisecondsorless.
`Some semiconductor automatic transfer switches can per-
`form switching as fast as one-half of a cycle, e.g., 8.3 milli-
`seconds, or even faster in someinstances. An automatictrans-
`fer switch capable of such high speed transfer times is
`referredto as a static transfer switch.
`FIG.2 is a circuit schematic that illustrates an example of
`a simple prior art solid state static transfer switch 50. The
`transfer switch 50 has twopairs ofsilicon controlledrectifiers
`(SCRs) 52 and 54 with onepair 52, also labeled Q1 and Q2,
`being arranged in a back-to-back configuration to enable one
`ofthe inputs 56, also labeled S1, to be connected a load 58 and
`the other pair 54, also labeled Q3 and Q4, being arranged
`back-to-back to enable the other one of the inputs 60, also
`labeled S2, to be connected to the load 58.
`During operation, SCRs Q1 and Q2 are turned on to con-
`nect input S1 to the load 58. Whereit is desired to connectthe
`other input S2 to the load 58, such as where someaspect of
`input S1 is not satisfactory, SCRs Q1 and Q2 are turned off
`and SCRs Q3 and Q4 are turned on. When SCRs Q3 and Q4
`are turned on, input S2 becomes connected to the load 58.
`Whereinput S1 represents utility power and input S2 repre-
`sents a source of backup power, operation of such a static
`transfer switch 50 can be controlled to switch from utility
`powerto backup power whenthe needarises.
`
`This inability to turn off an SCR underelectronic control in
`apredictable, repeatable, and consistent manneralso makesit
`difficult to guarantee that current flow to the load from one
`input source will be switched offbefore current flow from the
`other input source is switched on. Should current flow from
`both input sources end up being provided to the load at the
`sametime, such as what can happen ifthe control current does
`not reach a low enough value to cause the SCRs connected to
`the one input source to switch off in time before the other
`SCRsturn on connecting the load to the other input source,
`both input sources can end up becoming shorted together.
`Even though this might happen for onlya relatively short
`period of time, this kind of short circuiting can damage the
`transfer switch, can adversely impact operation of the load,
`can adversely affect other loads connected elsewhere to one
`or both input sources, and can even cause both input sources
`to catastrophically fail, leading to complete powerloss. This
`type of short circuiting is more commonly knownascross-
`conduction or shoot-though, and is a well-known failure
`modeofsolid-state transfer switches.
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`be turned off by simply telling it to “turn off” or by sendingit
`a “turn off” signal. By their inherent nature, an SCR will only
`break the electrical connection it has made between input and
`load when electrical current applied to its main or power
`terminal falls to a sufficiently low magnitude, typically zero,
`such that the SCR completely turns itself off. In certain
`instances when trying to turn an SCR off,
`it can take an
`unacceptably long time for the current to drop low enough for
`the SCRto actually turn off and break the flow ofpowerto the
`load. Sometimes, this delay can leave the load without power
`or sufficient quality power, which can adversely affect load
`operation. In somecases, its operation can cease and damage
`can occur.
`
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`
`To attempt to prevent this, solid state automatic transfer
`switches often have a great deal of built-in redundancy and
`typically require relatively complex control circuitry and con-
`trol logic. As a result, cost is undesirably increased andtheir
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`US 8,134,437 B2
`
`5
`required complexity alone compromises reliability. Where
`used for particularly critical transfer switching applications,
`monitoring, testing and maintenance requirements are more
`stringent andcostly, all of which is undesirable.
`Finally, because of packaging size constraints, SCRs, as
`with any type of solid state switch, are simply not able to meet
`certain international safety standards becausetheir terminals
`are inherently spaced too close together. Where these and
`other similarly stringent standards comeinto play, solid state
`switches typically cannot be used.
`While there are other types of solid state switches, their
`limitations are so great that they have found, at best, only
`limited use in transfer switches. For example, there are types
`of semiconductor switches,
`including bipolar transistors,
`insulated gate bipolartransistors IGBTs), metal oxide semi-
`conductor field effect transistors (MOSFETs), and others,
`that can be turned offvia a “turn off” signal. However,they all
`generally suffer from unacceptably high conduction losses in
`high current and high voltage applications, such as what is
`frequently encountered in transfer switching applications. In
`addition, they typically are not robust enough for most, if not
`virtuallyall, static transfer switch applications. For example,
`these types of semiconductor switches are often unable to
`withstand high short-circuit currents without failing or unde-
`sirably degrading in performance.
`Whatis neededis a switching arrangementthatis versatile,
`robust, and capable ofuse in transfer switching applications,
`including powertransfer switching applications. Whatis also
`needed is a switching arrangement that overcomesat least
`some of the aforementioned drawbacks and disadvantages.
`
`6
`magnet and the adjacent magnetic pole of the second perma-
`nent magnet. If desired,
`the drive coil can be disposed
`inwardly ofthe first permanent magnet. If desired, the drive
`coil can also be disposed outwardly of the second permanent
`magnet.
`In one preferred embodiment, the driven coil comprises an
`annular ring of one-piece, unitary and homogeneous con-
`struction and can be madeof a non-ferrous andelectrically
`conductive material. In one preferred construction, the annu-
`lar ring is comprised of aluminum. The use of a non-ferrous
`driven coil enablesit to be of lightweight, low mass construc-
`tion that can be moved more quickly enabling fast switching
`speeds to be achieved.
`In one preferred embodiment, the shorted turn comprises
`an armaturethat is reciprocable betweena retracted position
`and an extended position. The armature preferably is ofcylin-
`drical construction. A biasing element, such as a spring, can
`beused that biases the armature toward one or more switching
`positions.
`In one preferred embodiment, the armature is movable
`betweena first and second position with the biasing element
`always returning it to one of these two positions. Such an
`arrangement makesthe linear actuator well suited for use as a
`momentary transfer switch. In another preferred embodi-
`ment, the biasing elementretains the armature in the position
`to which it last was moved. The biasing element can be
`constructed to assist armature movement, such as when the
`drive coil propels it past a certain location.
`Wherethe linear actuator configured as part of a switch, the
`armature preferably is equipped with an electrical contact that
`makeselectrical contact with an electrical contact disposed
`offboard the actuator when disposed in one position andis
`movableto another position whereelectrical contact between
`the armature contact and the offboard contact is broken.
`The present invention provides an electromagnetic actua-
`In another preferred embodiment, the armature hasanelec-
`tor that is a componentof a switchthat preferably can be used
`trical contact and is movable betweena first position where
`in high speed electrical current switching applications. The
`the armature contact makes electrical contact with a first
`electromagnetic actuator preferably is a linear actuator com-
`electrical contact disposed offboard the linear actuator and a
`prising a fixed drive coil that is energized to move a shorted
`turn that is coaxial with the drive coil. The shorted turn
`second position where the armature contact makeselectrical
`contact with a secondelectrical contact disposed offboard the
`preferably is a driven coil that has at least one electrically
`
`conductive winding or turn. Thelinear actuator preferably is linear actuator. Suchalinear actuator preferably is ofbidirec-
`tional construction.
`equipped with a center pole over which the driven coil tele-
`scopically extends. In one preferred embodiment, the drive
`coilis fixed to the center pole, which preferably is made of a
`ferromagnetic material. In another preferred embodiment, the
`drive coil is fixed outside the driven coil.
`In one preferred embodiment, the center pole comprises a
`cylindrical rod that extends outwardly from a backstopthatis
`wider than the diameter of the center pole. During operation,
`the driven coil is movable betweena retracted position where
`it bears against the back stop and an extendedposition where
`it does not contact the back stop. In a preferred embodiment,
`the driven coil has padded stops at both ends ofits range of
`travel, stopping it in either the up or downposition. Whereit
`carries one or more contact, each contact can have a padded
`stop orthelike.
`In one preferred embodiment, the linear actuator prefer-
`ably includesa first permanent magnetdisposed outwardly of
`the driven coil and a second permanent magnetarrangement
`disposed inwardly of the driven coil. The permanent magnets
`can be arranged such that a magneticpole ofthe first perma-
`nent magnet has one polarity and is disposed facing and
`adjacent to the driven coil and a magnetic pole of the second
`permanent magnet has an opposite polarity and is disposed
`facing and adjacent to the driven coil. In one preferred
`embodiment, the driven coil is disposed in a gap located
`between the adjacent magnetic pole of the first permanent
`
`In one preferred linear actuator embodiment, the actuator
`includes a center pole that telescopically receives the arma-
`ture and includes a yoke disposed outwardly of the armature
`and the center pole with the yoke including a permanent
`magnet having its north and south poles disposed parallel to
`the direction of motion of the armature. The armature can
`include or carry an electrical contact with the yoke being
`spaced from the center pole defining a recess therebetween in
`which a contact can be disposed in the recess that makes
`electrical contact with the armature contact when the arma-
`
`ture is disposed in a first position and that does not make
`electrical contact with the armature contact when the arma-
`
`ture is disposed in a position spaced from the first position.
`In one preferred embodiment, the yoke is includes one or
`more portions made of ferromagnetic material and has a
`radially extending hub that forms a gap with the center pole in
`whichthe armature is disposed. In another preferred embodi-
`ment, the hub is disposed between the center pole and yoke
`and the armature is received in an annular gap in the hub.
`One preferred hub embodiment has a radially inwardly
`facing surface that opposesa radially outwardly facing sur-
`face of the hub between which the gap is defined. The drive
`coil preferably is disposed alongthe radially inwardly facing
`surface or the radially outwardly facing surface of the hub.In
`one preferred embodiment, the drive coil is of split coil con-
`
`SUMMARYOF THE INVENTION
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`Wherethe electromagnetic actuatoris a linear actuator, the
`armature can be reciprocated between the first and second
`positions during switch operation. In one preferred embodi-
`ment, the armature includes a driven coil that is electromag-
`netically driven to move the armature whena fixed drive coil
`is energized.
`The switch can include a biasing element that biases the
`includesan electromagnetic actuator having a movable arma-
`armature toward oneofthe first and second positions. In one
`ture or plungerthat carriesafirst electrical contact. There is a
`preferred embodiment, the biasing element