humphrey阀、Humphrey电磁阀、humphrey手动阀、humphrey气压阀、humphrey减压阀、humphrey止逆阀、humphrey梭动阀

上海航欧销售humphrey阀上海航欧机电设备有限公司从事进口机电设备、仪器仪表等疑难备品备件的销售,是经营世界各地进口设备机电配件的现代化企业。

上海航欧公司与众多品牌电子元件供应商建立有极其良好的合作关系,在欧美、日本等地形成了稳定、高效的供应网络,的询价渠道和多年的行业经验,更使我们在价格及货期上有很大优势。

经销产品供应的行业涉及冶金、钢铁、石化、能源、航天、集装箱码头、汽车、水利、造纸、电厂、纺织、注塑、橡胶、医疗、食品包装等。

我们热忱地希望尽我们的努力,力争优惠的产品价格,供货周期以及服务质量,能够为您解决进口备件方面的问题。

优势进口产品主要有:传感器,测速电机,接近开关,电子尺,编码器,控制器、分析仪,光纤,光栅,插装阀,电缆,拖链,分配器,马达,减速机,继电器、缓冲器和进口五金

humphrey阀、Humphrey电磁阀、humphrey手动阀、humphrey气压阀、humphrey减压阀、humphrey止逆阀、humphrey梭动阀

 

按钮型/杠杆型 2&3&4方向手动阀

125P、125HO、125T、125V、250P、250HO、250T、250V、250-4H

 

球塞型/柱塞杠杆型2&3方向机械作动阀

有125系列(125B、125MP、125MC、125MOC、125C)及250系列(250C)

 

圆配管型 2&3&4方向气压阀

型号(125A、125AA、125LA、125AH、250A、250AA、500A、501A、501AA、501-4A、501-4AA、590A)

 

TAC 级 2&3&4方向手动阀

型号(4P、4PP、4V、41P、41PP、41V、41TD3、41TS3、41TDS3、41RD3、41RS3、42P、42PP)

 

TAC 级 手动/机械操控配件

有滚珠型、滚子凸轮型、单向凸轮型、指压型脚踏型

34CW 34C 34B 34T 34F

 

TAC 级 气动操控配件(空压导引器)

34A 34AS 34AR 34ASR 341A

341AS 341AR 341ASR

 

TAC 级方向阀

减压阀,速度控制阀,止逆阀,梭动阀

 

快速型SQE排气阀 美国HUMPHREY快排阀QE4

HUMPHREY:TAC 4PP(TAC 4PP X2阀门)

美国HUMPHREY排气阀SQE-02 1/4接口

HUMPHREY:SQE1 1/8

HUMPHREY钮子开关E4V

HUMPHREY:062-4E1-20-AC220V

HUMPHREY:250A-3-10-21

HUMPHREY:250A-3-11-21

HUMPHREY:250AA 3 10 20

HUMPHREY:250AA

HUMPHREY:125AA 

HUMPHREY:125A

美国HUMPHREY:41pp

HUMPHREY电磁阀31E1  7.0W 120V 50/60  0-100 P.S.I.G 

HUMPHREY电磁阀M42E2  12VDC

HUMPHREY电磁阀MC41E1 MINI MYTE 12VDC 7.8W

HUMPHREY电磁阀TAC 341A

HUMPHREY电磁阀TAC E3P

HUMPHREY:QE3

HUMPHREY:QE4 

美国HUMPHREY梭阀Model:QE5

美国HUMPHREY快排阀SQE1

美国HUMPHREY排气阀SQE2

美国HUMPHREY快速排气阀QE2

手动气阀250-4H  

:: Air Piloted Valves           

 

Technical Section Poppet Diaphram Type

10-32, 1/8:, 1/4", 1/2", 3/4"

125A/AA, 125LA, 125AH

1/8" Product

250A/AA, 250-4A/4AA, 250AL, 250AH

1/4" Product

500A/AB/AG

1/2", 3/4" Product

590A/AB/AG

1/2", 3/4" Product

SS250A

1/4" Product

501A/AA-501-4A/AA

1/2", 3/4" Product

H/HA110 Air Piloted

10-32 Product

H/HA180 Air Piloted

1/8" Product

M/42A, M/42A2, (TAC3)

1/4" Product

SQE1, SQE2, QE2, QE3, QE4, QE5, SQE

1/8", 1/4", 3/8", 1/2", 3/4" Product

 

 

:: Air and Vacuum Piloted Valves    

 

VA125A, 250A, 500A, 590A

1/8", 1/4", 1/2", 3/4" Introduction

Y125N, Y205N, Y500IN, 125NI, 250IN

1/8", 1/4", 1/2" Product

R561, R332C, R332

1/8", 1/4" Product

 

 

:: Manual/Mechanical Air Valves     

 

Technical Section

1/8", 1/4"

125B, 125MP, 125MC, 125MOC, 125C, 250C Mechanical

1/8", 1/4" Product

125PLG, 250PL, 125P, 250P, 125HO, 250HO, 250E, 125T, 250T, 125V, 250V, 250-4H, 501V Manual/Foot

1/8", 1/4" Product

Seals Repair Kits and Parts

1/8", 1/4", 1/2", 3/4"

 

 

:: Solenoid Valves              

 

UL Recognized and UL Listed Valves

 

125E1LW

1/4" Product, How to Order

3E1 Mini-Mizer

10-32 Product, How to Order

555/565/575 Catalog

 

B3E1

10/32 2 position multi purpose 2 way 3 way

Conveyor Ad Reprint

 

H(V)010 Direct Acting In-Line

M3 Introduction and Dimensions

H010 4E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

H010 E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

H041 E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

H041 Indirect Acting In-Line

M3, Introduction, Dimensions

HA(V)010 Direct Acting Manifold

M3 Introduction and Dimensions

HA041 E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA041 Indirect Acting Manifold

M3, Introduction, Dimensions

HG010

M3 Specifications and Dimensions

HG010 E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HGA010 E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HK5 Valve

10-32, Product, How to Order

062/125 Tyna-Myte

1/4" Product

250 Electric

1/4" Product

310/410 In-Line

1/8" Dimensions

310/410 Technical Information

1/8" Dimensions

315

315/415 Product Catalog

315/415 Series Ad

 

500/501/590 Electric

1/2",3/4" Product

H030

HUMPHREY:320  24VCD 

HUMPHREY:310  DC24V   

HUMPHREY:310LL 120V 50/60HZ

HUMPHREY:S410 DC24V  

Humphrey电磁阀H180-4E2-PSL

HUMPHREY阀门250V-3-10-21

HUMPHREY阀门125V-3-10-22

HUMPHREY方向手动阀41V 

HUMPHREY:250A-3-11-20

HUMPHREY:062-4E1  220V

HUMPHREY:250A-3-11-21-BRB

HUMPHREY:7SP11/2FN

Humphrey电磁阀M401电压24V

HUMPHREY:MF21539

HUMPHREY:34C

HUMPHREY:SP21008A

HUMPHREY:BM208732

HUMPHREY:3P

HUMPHREY:4X1/410-32 Product, How to Order

H030 4E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

H030 E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

h283 4E2

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

H240 4E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

H240 4E2

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

H240 In-Line

1/4" Dimensions

H240 Serial Relay System

1/4" Product

H240 Technical Section

1/4"

H243 4E2

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA110 4E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA110 4E2

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA110 Subbase Mounted

10-32, Introduction, Dimensions

HA180 4E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA180 4E2

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA180 E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA180 Subbase Mounted

1/8" Introduction, How To Order, Dimensions

HA181 E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA240 4E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA240 4E2

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA240 Subbase Mounted

1/4" Dimensions

HA243 4E2

HUMPHREY:8-20-1

HUMPHREY:2.5X3/8

HUMPHREY:250E

HUMPPREY:42PP

HUMPHREY:2.5X1/4

HUMPHREY:MF21539

HUMPHREY:40137 5VDC

HUMPHREY:MC41E1 12VDC

名称︰ HUMPHREY手动阀/排气阀

型号︰ 全系列

品牌︰ HUMPHREY

原产地︰ 美国 

按钮型/杠杆型 2&3&4方向手动阀

125P、125HO、125T、125V、250P、250HO、250T、250V、250-4H

球塞型/柱塞杠杆型2&3方向机械作动阀

有125系列(125B、125MP、125MC、125MOC、125C)及250系列(250C)

圆配管型 2&3&4方向气压阀

型号(125A、125AA、125LA、125AH、250A、250AA、500A、501A、501AA、501-4A、501-4AA、590A)

TAC 级 2&3&4方向手动阀

型号(4P、4PP、4V、41P、41PP、41V、41TD3、41TS3、41TDS3、41RD3、41RS3、42P、42PP)

TAC 级 手动/机械操控配件

有滚珠型、滚子凸轮型、单向凸轮型、指压型脚踏型

34CW 34C 34B 34T 34F

TAC 级 气动操控配件(空压导引器)

34A 34AS 34AR 34ASR 341A

341AS 341AR 341ASR

TAC 级方向阀

减压阀,速度控制阀,止逆阀,梭动阀

快速型 SQE高性能快速排气阀

HUMPHREY相关产品

商:昆山点亿工业物资有限公司

减压阀,速度控制阀,止逆阀,梭动阀

快速型 SQE高性能快速排气阀

美国HUMPHREY排气阀SQE-02 1/4

美国HUMPHREY排气阀SQE1 1/8

HUMPHREY钮子开关E4V

D0006-14A 410  39.24VDC

HW240 Plug-in Subbased Mounted1/4" Dinmensions

M310/M410 Subbase Mounted1/8" Dimensions

R310/R410 Raceway Electrical Connector1/8" Dimensions

S310/S410 Stacking1/8" Dimensions

31E1/41E11/8" Product, How to Order

320/420 In-Line1/4" Dimensions

320/420 Technical Section1/4"

GEN2 Accumulation Conveyor ControlGEN2 Brochure

401/40210-32 Product, How to Order

42E1 TAC3 Electric1/4" Product

H040 4E1DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

H040 4E2DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

H040 Indirect Acting IN-LineM3 Introductions, and Dimensions

HA040 4E1DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA040 4E2DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA040 Indriect Acting ManifoldM3, Introductions, Dimensions

HA240 Air Piloted1/4" Product

HGF10DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HGF10, HGF15, HGF18Specifications, and Dimensions

HGF15DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HGF18DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

M420 Manifold Mounted1/4" Dimensions

  DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HEA/HEB and HJC/HJE

 

HW240 4E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HW240 4E2

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HW240 Plug-in Subbased Mounted

1/4" Dinmensions

M310/M410 Subbase Mounted:: TAC Air Valves         

 

Technical Section

10-32, 1/8"

2P,4P,4PP,4PPX,3P,31P,31PPX,41P, 41PP,41PPX,42P,42PP,42PA

10-32, 1/8" Product

2V,3V, 4V, 31V, 41V, 41T, 41R

10-32, 1/8" Product

RSR, SC1, C1 SQE, C125, S125

10-32, 1/8" Product

34A,341A,34AS,341AS,34AR,341AR, 34ASR,341ASR

10-32, 1/8" Product

34B, 34C, 34CW, 34CH, 34T, 34F

10-32, 1/8" Product

8-60, 8-600, 8-55A, ESB Switch

10-32, 1/8" Product

Miniature Fittings, BF, EF, Pf, 89-14, BF1,SEF, UEF, 110-21, PBF1, TF, UTF, 97-21, 150-31A, TCF, MBTF, URTF, 150-30A, TCF1,CF, RBF, NF, UXF, 40-13, RBF1, EXF, AM8, 151-20, BHF, SF, 100-35

1/8" Dimensions

R310/R410 Raceway Electrical Connector

1/8" Dimensions

S310/S410 Stacking

1/8" Dimensions

31E1/41E1

1/8" Product, How to Order

320/420 In-Line

1/4" Dimensions

320/420 Technical Section

1/4"

GEN2 Accumulation Conveyor Control

GEN2 Brochure

401/402

10-32 Product, How to Order

42E1 TAC3 Electric

1/4" Product

H040 4E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

H040 4E2

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

H040 Indirect Acting IN-Line

M3 Introductions, and Dimensions

HA040 4E1

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA040 4E2

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HA040 Indriect Acting Manifold

M3, Introductions, Dimensions

HA240 Air Piloted

1/4" Product

HGF10

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HGF10, HGF15, HGF18

Specifications, and Dimensions

HGF15

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

HGF18

DXF Drawings: NOTE: DXF files are in Metric. For NPT ports use "H" prefix.

M420 Manifold Mounted

1/4" Dimensions

 

:: TAC Air Valves

Technical Section10-32, 1/8"

2P,4P,4PP,4PPX,3P,31P,31PPX,41P, 41PP,41PPX,42P,42PP,42PA10-32, 1/8" Product

2V,3V, 4V, 31V, 41V, 41T, 41R10-32, 1/8" Product

RSR, SC1, C1 SQE, C125, S12510-32, 1/8" Product

34A,341A,34AS,341AS,34AR,341AR, 34ASR,341ASR10-32, 1/8" Product

34B, 34C, 34CW, 34CH, 34T, 34F10-32, 1/8" Product

8-60, 8-600, 8-55A, ESB Switch10-32, 1/8" Product

Miniature Fittings, BF, EF, Pf, 89-14, BF1,SEF, UEF, 110-21, PBF1, TF, UTF, 97-21, 150-31A, TCF, MBTF, URTF, 150-30A, TCF1,CF, RBF, NF, UXF, 40-13, RBF1, EXF, AM8, 151-20, BHF, SF, 100-35

上海航欧机电设备有限公司从事进口机电设备、仪器仪表等疑难备品备件的销售,是经营世界各地进口设备机电配件的现代化企业。

上海航欧公司与众多品牌电子元件供应商建立有良好的合作关系,在欧美、日本等地形成了稳定、高效的供应网络,的询价渠道和多年的行业经验,更使我们在价格及货期上有很大优势。

经销产品供应的行业涉及冶金、钢铁、石化、能源、航天、集装箱码头、汽车、水利、造纸、电厂、纺织、注塑、橡胶、医疗、食品包装等。

我们热忱地希望尽我们的努力,力争优惠的产品价格,供货周期以及服务质量,能够为您解决进口备件方面的问题。

优势进口产品主要有:传感器,测速电机,接近开关,电子尺,编码器,控制器、分析仪,光纤,光栅,插装阀,电缆,拖链,分配器,马达,减速机,继电器、缓冲器和进口五金等。

STENFLEX          AS-1 DN125 PN16 法兰特制  查询现货         膨胀节

STENFLEX          AS-1 DN150 Length:150mm PN16 AISI 316Ti ASA150lbs     查询现货         膨胀节

STENFLEX          AS-1 DN150 PN16    查询现货         膨胀节

STENFLEX          AS-1 DN150 PN16 1.4571         查询现货         膨胀节

STENFLEX          AS-1 DN250 PN16    查询现货         膨胀节

STENFLEX          AS-1 DN32  PN16   查询现货         膨胀节

STENFLEX          AS-1 DN50 ASA 150lbs     查询现货         膨胀节

STENFLEX          AS-1 DN50 PN16 length:125mm  查询现货         膨胀节

STENFLEX          AS-1 DN65 PN16  125mm      查询现货         膨胀节

STENFLEX          AS-1 DN80 PN16      查询现货         膨胀节

ASAHI KEIKI    AS-101-2A-4 DC24V          查询现货         数显仪

DEUFRA   AS-P  400V 50HZ    查询现货         电控单元

ARbiter    AS0044600      查询现货         天线安装支架

ARbiter    AS0094500       查询现货         避雷器

NK technologies       AS1-NOU-FT     查询现货         NK technologies

NK technologies       AS1-NOU-FT-GO       查询现货         传感器

AXILEC     AS1200 220Vac/48Vdc –25A 1200W - boitier QE 查询现货         电源

MFZ AS210B    查询现货         主板

MINCO     AS215791PDPD3S300C40D160       查询现货         传感器

WANDFLUH    AS22060b-R230        查询现货         电磁阀

NK technologies       AS3-NODC-FF   查询现货         电流变送器

M-SYSTEM        AS4V-Z15-R     查询现货         模块

ROBOX     AS5026.001 A040114       查询现货         处理器电路板

ROBOX     AS5034.010 A041441       查询现货         处理器电路板

SIKO AS510/1-0001  查询现货         编码器

MINCO     AS5200PD45X1S       查询现货         温度传感器

ASTEC       ASA01A18-L     查询现货         ASTEC

LUMBERG        ASB-8/LED 5-4-331/5M   查询现货         集线器

LUMBERG        ASBS 8/LED 5-4         查询现货         传感器分配盒

LUMBERG        ASBS6 LED-5/4          查询现货         6孔线路板

LUMBERG        ASBSM 8/LED 3       查询现货         传感器

LUMBERG        ASBSV 4/LED 5          查询现货         连接器

LUMBERG        ASBSV 8/LED 5          查询现货         连接器

LUMBERG        ASBSV-8/LED-5         查询现货         集线器

automation direct  ASD-32-24D     查询现货         阀

MBS ASK 101.4  1600/5A  10VA cl.1    查询现货         电流互感器

MBS ASK 103.3  1000/1A 10VA      查询现货         互感器

MBS ASK 103.3  800/5A  15VA cl.1      查询现货         互感器

MBS ASK 103.3 2500/1A 10VA          查询现货         互感器

MBS ASK 123.3  3000/5A  15VA cl.1    查询现货         互感器

MBS ASK 127.6  4000/5A  15VA cl.1    查询现货         互感器

MBS ASK 127.6  4000/5A  30VA cl.1    查询现货         互感器

MBS ASK 21.3  150/5A  1.5VA cl.1       查询现货         互感器

MBS ASK 21.3  250/5A  1.5VA cl0.5     查询现货         互感器

MBS ASK 21.3  50/5A  1VA cl.1    查询现货         互感器

MBS ASK 21.3  75/5A  1.5VA cl.1          查询现货         互感器

MBS ASK 21.3 100/5A 1,5VA Kl.1     查询现货         电流互感器

MBS ASK 31.3   150/1A   2.5VA 查询现货         互感器

MBS ASK 31.3  100/5A  1.5VA cl.1       查询现货         互感器

MBS ASK 31.3  100/5A  2.5VA cl.0.5    查询现货         电流互感器

MBS ASK 31.3  200/5A  2.5VA cl.1       查询现货         电流互感器

MBS ASK 31.3  200/5A  5VA cl.1  查询现货         互感器

MBS ASK 31.3  300/5A  5VA cl.1  查询现货         互感器

MBS ASK 31.3  500/5A  2.5VA Cl.1       查询现货         电流互感器

MBS ASK 31.3  600/5A  2.5VA cl.1       查询现货         电流互感器

MBS ASK 31.3  75/5A  1.5VA cl.1          查询现货         互感器

MBS ASK 31.3 160/5 2.5VA      查询现货         电流互感器

MBS ASK 31.3, 100/5A, 2.5VA K1.1 查询现货         互感器

MBS ASK 31.4  250/5A  10VA cl.1         查询现货         互感器

MBS ASK 31.4  400/5A  10VA cl.1         查询现货         电流互感器

MBS ASK 31.4  600/5A  10VA cl.1         查询现货         互感器

MBS ASK 31.4 100/5A 2,5VA Kl.1     查询现货         电流互感器

MBS ASK 31.4 150/5A 5VA Kl.1         查询现货         电流互感器

MBS ASK 31.4 250/5A 2.5VA K0.5    查询现货         电流互感器

MBS ASK 31.4 400/5A 2.5VA K0.5    查询现货         电流互感器

MBS ASK 31.4 60/5A 1,5VA Kl.1       查询现货         电流互感器

MBS ASK 31.5  300/1A  5VA cl.0.5       查询现货         互感器

MBS ASK 41.3 750/5A 2.5VA cl.1     查询现货         互感器

MBS ASK 41.4   100/1A   2.5VA 查询现货         互感器

MBS ASK 41.4   200/1A   2.5VA  KI.0.5    查询现货         互感器

MBS ASK 41.4   300/1A   10VA  查询现货         互感器

MBS ASK 41.4   400/1A   10VA  查询现货         互感器

MBS ASK 41.4   500/1A   10VA  查询现货         互感器

MBS ASK 41.4  600/5A  5VA cl.1  查询现货         互感器

MBS ASK 41.4 100/5A 2,5VA Kl.1     查询现货         互感器

MBS ASK 41.4 150/5A 5VA Kl.1         查询现货         互感器

MBS ASK 41.4 250/5A 10VA Kl.1      查询现货         互感器

MBS ASK 41.4 400/5A 10VA CL.1     查询现货         电流互感器

MBS ASK 41.4 600/1A 10VA Kl.1      查询现货         电流互感器

MBS ASK 41.4 600/5A 15VA Kl.1      查询现货         电流互感器

MBS ASK 41.4 75/5A 1,5VA Kl.1       查询现货         互感器

MBS ASK 412.4  100/5A  3.75VA cl.1   查询现货         电流互感器

MBS ASK 412.4  300/5A  10VA cl.1      查询现货         电流互感器

MBS ASK 412.4  500/5A  10VA cl.1      查询现货         电流互感器

MBS ASK 51.4  750/5A  10VA cl.1         查询现货         电流互感器

MBS ASK 541.4  800/5A  15VA cl.1      查询现货         互感器

MBS ASK 61.4    750/1A   10VA         查询现货         互感器

MBS ASK 61.4   600/1A    10VA        查询现货         互感器

MBS ASK 61.4  1600/5A; 15VA; CLASS 1         查询现货         电流变换器

MBS ASK 61.4 1250/1A 5VA Kl.1      查询现货         电流互感器

MBS ASK 61.4 400/1A 2.5VA KL.1    查询现货         电流互感器