(12) United States Patent
`Brooks
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 8,134,437 B2
`Mar. 13, 2012
`
`USOO8134437B2
`
`(54) EDDY CURRENT INDUCTIVE DRIVE
`ELECTROMECHANICAL LINEAR
`ACTUATOR AND SWITCHING
`ARRANGEMENT
`
`(75) Inventor: Elliot Brooks, Foothill Ranch, CA (US)
`(73) Assignee: PowerPath Technologies LLC, San
`Juan Capistrano, CA (US)
`p
`s
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 142 days.
`11/920,785
`
`(*) Notice:
`
`(21) Appl. No.:
`
`May 20, 2006
`PCT/US2006/O19779
`
`(22) PCT Filed:
`(86). PCT No.:
`S371 (c)(1),
`Mar. 2, 2009
`(2), (4) Date:
`(87) PCT Pub. No.: WO2006/127628
`PCT Pub. Date: Nov.30, 2006
`
`(65)
`
`3, 1935 Rhine
`1993,946 A
`E. Eston
`3. A
`aC
`2,488.443 A 11/1949 Sonnemann
`3,001,115. A
`9, 1961 Gendreu
`3,162,796 A 12/1964 Schreiber
`3,176,170 A
`3, 1965 Fulton
`3,417,268 A 12/1968 Lace
`3,505,544 A
`4, 1970 Helms
`3,585,458 A
`6, 1971 Yoshimura
`3,599,020 A
`8, 1971 Harris
`3,619,673 A 11, 1971 Hel
`(Conti e s
`O1
`FOREIGN PATENT DOCUMENTS
`O 364308
`4f1990
`(Continued)
`
`EP
`
`OTHER PUBLICATIONS
`Zieve, Low Voltage Electromagnetic Riveter, Electroimpact, Inc.,
`Oct. 21, 1986.
`
`(Continued)
`
`Primary Examiner — Ramon Barrera
`(74) Attorney, Agent, or Firm — D. Stein
`
`Prior Publication Data
`ABSTRACT
`(57)
`US 2009/0212889 A1
`Aug. 27, 2009
`The present invention is directed to an inductively driven
`(51) Int. Cl
`electromagnetic linear actuator arrangement employing eddy
`(2006.01)
`iotF 7/08
`currents induced by a fixed drive coil to drive its armature.
`im.
`(52) U.S. Cl. ........ 335/222:335/100; 335/147; 3.6 Eddy current focusing fields are employed to direct the eddy
`currents using Lorentz forces to maximize armature speed.
`The armature includes a shorted driven coil in a 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
`ground fault interrupter applications.
`
`(58) Field of Classification Search .................. 335/100,
`S
`lication file f ER." 245
`ee application file for complete search history.
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
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`7, 1921 MacLaren
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`4, 1929 Petersen
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`4/1934 Pridhan
`
`
`
`28 Claims, 20 Drawing Sheets
`
`1
`
`APPLE 1031
`
`

`

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`5,070,252
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`5,081,367
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`5,081,381
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`5,177,383
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`Rosa
`11, 1993
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`Prescott
`Mody
`5, 1995
`5,420,468
`
`US 8,134,437 B2
`Page 2
`
`7, 1995 Stuart
`5.434.458 A
`8, 1995 Denne
`5,440,183 A
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`5,528, 113 A
`5,576,604 A 11/1996 Kunert
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`5/1997 Stephany
`5,638,948 A
`6, 1997 Sharaf
`5,644,175 A
`7, 1997 Galm
`5,694,098 A 12/1997 Mody
`5,694,312 A 12, 1997 Brand
`5,698,911 A 12, 1997 Dunfield
`5,701,040 A 12/1997 Orlowska
`5,717,552 A
`2f1998 Varian
`5,727,932 A
`3, 1998 McGrath
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`3/1998 Hallidy
`5,748,432 A
`5/1998 Przywozny
`5,780,990 A
`7, 1998 Weber
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`9, 1998 Zhao
`5,814,907 A * 9/1998 Bandera .......................... 310, 14
`5,864,274 A
`1/1999 Steingroever
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`5/1999 Elenbaas
`5,914.467 A
`6/1999 Jonas
`5,920,129 A
`7, 1999 Smith
`6,015,273 A
`1/2000 Hannagan
`6,028,499 A
`2/2000 Oudet
`6,100,604. A
`8, 2000 Morroni
`6,100,605 A
`8/2000 Zajkowski
`6,137,195 A 10/2000 Chitayat
`6,176,208 B1
`1/2001 Tsuzuki
`6,208.497 B1
`3/2001 Seale
`6,252,315 B1
`6/2001 Heo
`6.297,640 B1
`10/2001 Hayes
`6,312.434 B1
`1 1/2001 Sutrina
`6,326,710 B1
`12/2001 Guenther
`6,357,359 B1
`3/2002 Davey
`6,365,993 B1
`4/2002 Calhoon
`6,409,144 B1
`6/2002 Inami
`6,445,092 B1
`9, 2002 Marder
`6,483,682 B1
`1 1/2002 Reynolds
`6,542,023 B1
`4/2003 Daun-Lindberg
`6,560,128 B1
`5/2003 Rajda
`6,577,216 B2
`6/2003 Turner
`6,590,481 B2
`7/2003 Turner
`6,593,670 B2
`7/2003 Anderson
`6,603.224 B1
`8/2003 Hollingsworth
`6,608.408 B1
`8, 2003 Denne
`6,611,078 B1
`8, 2003 Durham
`6,624,720 B1
`9, 2003 Allison
`6,639,496 B1
`10/2003 van Namen
`6,639,759 B2 10/2003 Inoguchi
`6,664,663 B1 12/2003 Yeo
`6,700,351 B2
`3, 2004 Blair
`6,721,641 B1
`4/2004 Denne
`6,750,576 B2
`6/2004 Ehrhart
`6,765,157 B2
`7/2004 Rademacher
`6,768,223 B2
`7, 2004 Powell
`6,770,988 B2
`8, 2004 Denne
`6,836.201 B1* 12/2004 Devenyi et al. ............... 335,229
`6,879,060 B2
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`6,917, 124 B2
`7/2005 Shetler, Jr.
`2002fO080531 A1
`6/2002 Inoguchi
`FOREIGN PATENT DOCUMENTS
`545712
`6, 1942
`OTHER PUBLICATIONS
`Zieve at al., High Force Density Eddy Current Driven Actuator,
`Electroimpact, Inc., 1988.
`Zieve et al., Advanced EMR Technology, 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 EMR with Spring-Damper Handle,
`Electroimpact, Inc. Sep. 20, 2000.
`* cited by examiner
`
`GB
`
`2
`
`

`

`U.S. Patent
`U.S. Patent
`
`Mar. 13, 2012
`Mar.13, 2012
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`Sheet 1 of 20
`Sheet 1 of 20
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`US 8,134,437 B2
`US 8,134,437 B2
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`2 3
`
`8
`
`Fig. 1 (Prior Art)
`
`56
`
`\ Me
`
`
`
`81
`
`Load
`
`60 YO
`
`$2
`
`3
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`

`

`U.S. Patent
`U.S. Patent
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`Mar.13, 2012
`Mar. 13, 2012
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`Mar. 13, 2012
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`US 8,134,437 B2
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`190
`190
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`92
`192
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`2
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`112
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`108
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`
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`192
`
`190 122
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`80"
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`5
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`U.S. Patent
`U.S. Patent
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`\\. LL
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`190
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`94!
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`6
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`6
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`U.S. Patent
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`Mar. 13, 2012
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`Sheet 5 of 20
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`US 8,134,437 B2
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`
`
`1
`
`86
`
`Limca
`
`of Vmc "/ N
`Rmc &
`2
`lmc
`S
`
`- T Mechanical
`Motion
`
`7
`
`

`

`U.S. Patent
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`Mar. 13, 2012
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`Sheet 6 of 20
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`US 8,134,437 B2
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`
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`176 -
`-- "Down"
`Source 2 O)
`
`78
`
`86
`
`on Ceil 3
`-
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`-ie- 84
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`8
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`U.S. Patent
`U.S. Patent
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`Mar. 13, 2012
`Mar.13, 2012
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`Sheet 7 of 20
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`US 8,134,437 B2
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`2O
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`224
`224
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`222
`
`210
`
`80'
`80'
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`210
`
`C.
`
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`
`N
`
`RS
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`s
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`26
`216
`
`208
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`212
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`224
`224
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`9
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`U.S. Patent
`U.S. Patent
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`Mar. 13, 2012
`Mar.13, 2012
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`Sheet 8 of 20
`Sheet 8 of 20
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`US 8,134,437 B2
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`222
`222
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`2O
`210
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`214
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`
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`22
`
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`222
`
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`
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`N
`
`24
`
`216
`216
`
`202
`202
`
`202
`202
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`204 226 224
`
`Fig. 10
`Fig. 10
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`10
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`10
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`

`

`U.S. Patent
`U.S. Patent
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`Mar. 13, 2012
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`Sheet 9 of 20
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`US 8,134,437 B2
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`80'
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`80'ao /
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`20 /
`
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`226
`226
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`208
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`226
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`
`11
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`U.S. Patent
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`Mar. 13, 2012
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`Sheet 10 of 20
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`US 8,134,437 B2
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`
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`risug
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`Time
`
`g
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`Drive. From Doy? to Up
`
`Dris. From Up to Down
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`246
`
`Fig. 13
`
`Fig. 14
`
`12
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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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`Writage
`
`tags
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`gate Drives: From on to lp.
`
`Gate Dries: Frtin Lp to D
`
`F
`
`FiO. 5
`
`Fig. 16
`
`258
`
`252 /
`
`
`
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`Gate
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`
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`
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`
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`
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`\ solated
`is Sata
`five
`
`262
`
`260
`
`
`
`
`
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`13
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`U.S. Patent
`U.S. Patent
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`Mar. 13, 2012
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`OO
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`100
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`14
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`U.S. Patent
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`Mar. 13, 2012
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`Sheet 13 of 20
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`US 8,134,437 B2
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`Load
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`15
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`U.S. Patent
`U.S. Patent
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`Mar. 13, 2012
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`16
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`16
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`N
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`92
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`U.S. Patent
`U.S. Patent
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`Mar. 13, 2012
`Mar.13, 2012
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`Sheet 15 of 20
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`US 8,134,437 B2
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`298
`N
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`44
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`30"
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`
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`17
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`

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`U.S. Patent
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`Mar. 13, 2012
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`Sheet 16 of 20
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`US 8,134,437 B2
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`306
`36 -
`
`so
`
`-
`
`--
`
`3O8 J.
`
`-- 38
`
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`
`326
`
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`
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`
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`
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`
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`
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`18
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`

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`U.S. Patent
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`Mar. 13, 2012
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`Sheet 17 of 20
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`334
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`19
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`19
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`U.S. Patent
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`Mar. 13, 2012
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`Sheet 18 of 20
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`US 8,134,437 B2
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`S
`
`
`
`320
`
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`
`- Cff-S$88
`----
`
`326
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`
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`
`to
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`
`pil
`grad
`
`Sf
`
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`
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`
`328
`
`20
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`

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`U.S. Patent
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`Mar. 13, 2012
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`Sheet 19 of 20
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`US 8,134,437 B2
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`-
`81 f-
`
`X
`
`2
`
`82 fl
`
`
`
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`Tfailsfief
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`
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`
`Load
`
`l
`
`La
`
`Lai
`
`Fig. 28
`
`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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`340
`
`
`
`
`
`
`
`Electronically OpenClose
`Circuit Breaker
`
`Redundant labork
`
`ago H
`
`Load
`OS
`
`
`
`
`
`
`
`342
`
`
`
`
`
`340
`
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`Circuit Breaker
`
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`
`
`
`Electronically OpenClose
`Circuit Breaker
`
`342
`
`mammap
`
`Radundatlatlik
`Collectil
`
`Fig. 29
`
`22
`
`

`

`US 8,134,437 B2
`
`1.
`EDDY CURRENT INDUCTIVE DRIVE
`ELECTROMECHANICAL LINEAR
`ACTUATOR AND SWITCHING
`ARRANGEMENT
`
`CROSS REFERENCE TO RELATED
`APPLICATION
`
`This application claims all benefits of and priority under 35
`U.S.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
`
`10
`
`15
`
`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
`power Supplies, distributed power Switches, automatic trans
`fer switches and static transfer switches.
`
`BACKGROUND OF THE INVENTION
`
`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 power from utility power to
`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 source of electrical
`power before making the electrical connection with the other
`Source of 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 the first input. In power Switching applications, a “make
`before-break' power transfer switch allows a hot-to-hot
`transfer without loss of 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 delayed transition transfer switch. Delayed tran
`sition transfer Switches are 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 the first input before making the connection
`with the second input. A time delay after breaking the first
`connection is provided Sufficient to permit magnetic fields 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. When it 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 in a
`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, movement of 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 includes a 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 toward it in the manner depicted in FIG. 1.
`Although not shown in 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, due at least in part
`to its relatively high inertia armature construction, Solenoid
`actuators 40 have undesirably slow response times, which
`limits Switching speeds and transfer times when used in 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
`tromechanical transfer Switch actuators do nothing to remedy
`the deficiencies found in the aforementioned solenoid actua
`
`There are many types of electrical switches that have been
`used in the past for Switching electrical current. In its most
`simplest form, a Switch has two electrically conductive con
`tacts that touch each other to allow electrical current to flow
`through a circuit, “making the circuit, and that are separated
`when it 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 the like.
`Some types of mechanical 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 move the Switch to 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
`Some sort of an input into motion that moves the Switch to the
`desired position. Operation of a Switch actuator is typically
`controlled in some sort of automated manner. For example, a
`sensor, Such as a Voltage sensor, a current sensor, a tempera
`ture sensor or another kind of a sensor or sensor arrangement
`can be used to provide an input to the actuator that causes it to
`move a Switch to a desired position.
`Not only can such switches be used to turn power on or off,
`they can also be employed to switch between two or more
`different inputs or sources, including, among other things,
`power sources. A switch used to switch between two different
`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 move the transfer switch to
`the desired position.
`Manual transfer Switches are usually mechanical and are
`used to manually switch between two different inputs or
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`tors. In fact, these types of actuators are often part of a rela
`tively complex transfer Switch mechanism that includes
`cams, gears, linkages and the like. Not only are such transfer
`Switch mechanisms unacceptably slow for more demanding
`transfer Switch applications, their components can undesir
`ably wear over time or even stick, if not frequently tested,
`resulting in premature or even unexpected failure.
`Where a transfer switch is automatically controlled, it is
`commonly referred to as an automatic transfer switch or ATS.
`Electromechanical automatic transfer Switches utilize an
`electromagnetic actuator, Such as anaforementioned Solenoid
`or rotary or stepper motor actuator. Solid state automatic
`transfer switches, as discussed in more detail below, utilize
`semiconductor Switching technology and are used in transfer
`Switching applications where fast Switching is required.
`While transfer switches that employ an electromagnetic
`actuator have enjoyed substantial commercial Success,
`improvements nonetheless remain desirable. For example,
`conventional Solenoid actuators and rotary stepper motor
`actuators in the past have been inherently slow operating,
`limiting their use to Switching applications tolerant of their
`slow Switching speeds and slow transfer times.
`With specific regard to automatic transfer Switching appli
`cations, it has been a challenge to achieve transfer times faster
`than about seven alternating current cycles, e.g., less than 120
`milliseconds where sixty hertz, alternating current is used,
`using a transfer Switch that is electromagnetically actuated.
`Indeed, it has been believed heretofore unknown to achieve
`transfer times faster than two cycles, e.g., less than 33.3
`milliseconds where sixty hertz, alternating current is used, in
`an automatic transfer Switch that 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 power loss during Switching.
`Where faster transfer or switching times are required,
`semiconductor or solid state transfer Switches are used. These
`are used for more critical transfer Switching applications,
`including those where the load cannot tolerate 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 performed in 17 milliseconds or less.
`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 some instances. An automatic trans
`fer switch capable of such high speed transfer times is
`referred to 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
`50
`transfer switch 50 has two pairs of silicon controlled rectifiers
`(SCRs) 52 and 54 with one pair 52, also labeled Q1 and Q2,
`being arranged in a back-to-back configuration to enable one
`of the 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. Where it is desired to connect the
`other input S2 to the load 58, such as where some aspect 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.
`Where input 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
`power to backup power when the need arises.
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`Thyristors or SCRs are typically used in solid state transfer
`switches because they are more robust, have lower power
`losses, and can be used with simpler low-power control
`arrangements than other types of semiconductor Switches.
`SCRs are particularly well suited for high power switching
`applications because of their ability to switch electrical cur
`rents ranging from a few amps up to a few thousand amps,
`which can amount to millions of watts in some power Switch
`ing applications.
`Unfortunately, SCRs have certain disadvantages. For
`example, SCRS dissipate more power than electromechani
`cally actuated transfer Switches sometimes producing a sig
`nificant amount of heat during operation. As a result, cost and
`complexity is often increased as additional equipment may be
`needed to remove the heat produced by the SCRs. Where heat
`transfer equipment is needed, transfer Switch maintenance
`and monitoring costs typically are undesirably increased.
`Another drawback lies in the fact that SCRs always require
`a Supply of control power to maintain connection between an
`input source and the load. Should the control power to the
`transfer switch fail, all of the SCRs will switch off, breaking
`each and every connection between input and load. To prevent
`this from happening, Solid State transfer Switches are usually
`equipped with redundant power Supplies. Unfortunately, the
`level of redundancy typically required to ensure reliable and
`stable operation undesirably increases its purchase price,
`adds to complexity, and requires additional monitoring and
`maintenance, all of which is undesirable and adds to overall
`operational costs.
`A still further drawback lies in the fact that an SCR cannot
`be turned off by simply telling it to “turn off or by sending it
`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 longtime for the current to drop low enough for
`the SCR to actually turn off and break the flow of power to the
`load. Sometimes, this delay can leave the load without power
`or sufficient quality power, which can adversely affect load
`operation. In some cases, its operation can cease and damage
`Cal OCC.
`This inability to turn offan SCR under electronic control in
`a predictable, repeatable, and consistent manner also makes it
`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
`same time, such as what can happen if the 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
`SCRS turn on connecting the load to the other input source,
`both input sources can end up becoming shorted together.
`Even though this might happen for only a 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 power loss. This
`type of short circuiting is more commonly known as cross
`conduction or shoot-though, and is a well-known failure
`mode of solid-state transfer switches.
`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 and their
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`US 8,134,437 B2
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`5
`required complexity alone compromises reliability. Where
`used for particularly critical transfer Switching applications,
`monitoring, testing and maintenance requirements are more
`stringent and costly, all of which is undesirable.
`Finally, because of packaging size constraints, SCRS, as
`with any type of solid state Switch, are simply notable to meet
`certain international safety standards because their terminals
`are inherently spaced too close together. Where these and
`other similarly stringent standards come into 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 bipolar transistors (IGBTs), metal oxide semi
`conductor field effect transistors (MOSFETs), and others,
`that can be turned off via 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
`virtually all, 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.
`What is needed is a Switching arrangement that is versatile,
`robust, and capable of use in transfer Switching applications,
`including power transfer Switching applications. What is also
`needed is a Switching arrangement that overcomes at least
`Some of the aforementioned drawbacks and disadvantages.
`
`SUMMARY OF THE INVENTION
`
`6
`magnet and the adjacent magnetic pole of the second perma
`nent magnet. If desired, the drive coil can be disposed
`inwardly of the 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 made of a non-ferrous and electrically
`conductive material. In one preferred construction, the annu
`lar ring is comprised of aluminum. The use of a non-ferrous
`driven coil enables it 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 armature that is reciprocable between a retracted position
`and an extended position. The armature preferably is of cylin
`drical construction. A biasing element. Such as a spring, can
`be used that biases the armature toward one or more Switching
`positions.
`In one preferred embodiment, the armature is movable
`between a first and second position with the biasing element
`always returning it to one of these two positions. Such an
`arrangement makes the linear actuator well Suited for use as a
`momentary transfer switch. In another preferred embodi
`ment, the biasing element retains 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.
`Where the linear actuator configured as part of a switch, the
`armature preferably is equipped with an electrical contact that
`makes electrical contact with an electrical contact disposed
`offboard the actuator when disposed in one position and is
`movable to another position where electrical contact between
`the armature contact and the offboard contact is broken.
`In another preferred embodiment, the armature has an elec
`trical contact and is movable between a first position where
`the armature contact makes electrical contact with a first
`electrical contact disposed offboard the linear actuator and a
`second position where the armature contact makes electrical
`contact with a second electrical contact disposed offboard the
`linear actuator. Such a linear actuator preferably is of bidirec
`tional construction.
`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 centerpole in
`which the 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 opposes a radially outwardly facing Sur
`face of the hub between which the gap is defined. The drive
`coil preferably is disposed along the 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
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`The present invention provides an electromagnetic actua
`tor that is a component of a switch that preferably can be used
`in high speed electrical current Switching applications. The
`electromagnetic actuator preferably is a linear actuator com
`prising a fixed drive coil that is energized to move a shorted
`turn that is coaxial with