變頻技術是應交流電機無級調速的需要而誕生的。20世紀60年代以后，電力電子器件經歷了SCR(晶閘管)、GTO(門極可關斷晶閘管)、BJT(雙極型功率晶體管)、MOSFET(金屬氧化物場效應管)、SIT(靜電感應晶體管)、SITH(靜電感應晶閘管)、MGT(MOS控制晶體管)、MCT(MOS控制晶閘管)、IGBT(絕緣柵雙極型晶體管)、HVIGBT(耐高壓絕緣柵雙極型晶閘管)的發(fā)展過程，器件的更新促進了電力電子變換技術的不斷發(fā)展。20世紀70年代開始，脈寬調制變壓變頻(PWM－VVVF)調速研究引起了人們的高度重視。20世紀80年代，作為變頻技術核心的PWM模式優(yōu)化問題吸引著人們的濃厚興趣，并得出諸多優(yōu)化模式，其中以鞍形波PWM模式效果最佳。20世紀80年代后半期開始，美、日、德、英等發(fā)達國家的VVVF變頻器已投入市場并獲得了廣泛應用。
ALLEN BRADLEY 1745-C3 SER.A *NEW NO BOX*
ALLEN BRADLEY 592-BOV4 (Brand New Current Factory Packaging)
ALLEN BRADLEY 1489-AMCL312 (Brand New Current Factory Packaging)
ALLEN BRADLEY 148363 REV.03 PC CONTROL BOARD *USED*
ALLEN BRADLEY 802DN-AD5 (Surplus New not in factory packaging)
ALLEN BRADLEY OD155 (Surplus New In factory packaging)
Allen Bradley 1771-ig New factory packing
ALLEN BRADLEY F0038-00146 (Surplus New not in factory packaging)
Allen Bradley 1492CB3H400 NSFP **GENUINE** AB 1492 CB3 H 400
ALLEN BRADLEY 600-TAX4 SERIES B SWTICHES
ALLEN BRADLEY 700-P1000A1 (Surplus New In factory packaging)
ALLEN BRADLEY SP-50404 (Surplus New not in factory packaging)
ALLEN BRADLEY 599-PL34D (Surplus New In factory packaging)
ALLEN BRADLEY 855T-B24FN3 (Brand New Current Factory Packaging)
ALLEN BRADLEY 500-B0D92 SER.A MOTOR STARTER SIZE 1 *USED*
ALLEN BRADLEY 42RSU-6205-QB SER.B *USED*
ALLEN BRADLEY 1489-M3C160 (Brand New Current Factory Packaging)
Allen Bradley 802MAZJ1LF NSNP **GENUINE** AB802MAZJ1LF
ALLEN BRADLEY 74-A288 (Surplus New not in factory packaging)
ALLEN BRADLEY 1201-HAB (Brand New Current Factory Packaging)
Allen Bradley 2090XXNPMP16S07 NSFP **GENUINE** AB 2090 XXNPMP 16S07
ALLEN BRADLEY 1497-N37 (Used, Cleaned, Tested 2 year warranty)
Allen Bradley 871ZBW5C18N3 NSFP **GENUINE** AB 871Z BW5C18 N3
ALLEN BRADLEY 937TH-DISRS-DC1 (Surplus New In factory packaging)
ALLEN BRADLEY 190-A40A(Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY ABR-3200 (Surplus New not in factory packaging)
ALLEN BRADLEY140G-G2C3-C40 (Surplus New not in factory packaging)
ALLEN BRADLEY 194R-NN030P34R2 (Surplus New not in factory packaging)
ALLEN BRADLEY 2755-CG15 (Surplus New In factory packaging)
ALLEN BRADLEY 700-P401A1 (Surplus New In factory packaging)
ALLEN BRADLEY 4042148401R254 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 705-ACD-D36 (Surplus New not in factory packaging)
ALLEN BRADLEY 20-750-ACTE1-F6 (Surplus New In factory packaging)
ALLEN BRADLEY 500-AAD930 (Surplus New not in factory packaging)
ALLEN BRADLEY 6189-DIMM64 (Surplus New In factory packaging)
ALLEN BRADLEY 319624-A03 (Surplus New not in factory packaging)
ALLEN BRADLEY 802T-A3 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 193-HIM1 (Surplus New not in factory packaging)
ALLEN BRADLEY 836-C8 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 42GRR-9003-QD1 SERIES A *USED*
ALLEN BRADLEY 702-BAD-92 (Surplus New In factory packaging)
ALLEN BRADLEY 501444 CIRCUIT BOARD *USED*
ALLEN BRADLEY 80025-455-01-R (Surplus New not in factory packaging)
ALLEN BRADLEY 700DC-NT200Z24 (Surplus New not in factory packaging)
ALLEN BRADLEY 6218-919 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 6228-491 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 6223-511 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 5602-973 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 6217-621 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 1746-A7 SLC 500 7-SLOT RACK (14D0)
Allen Bradley 42SMF7100 NSNP **GENUINE** AB 42SMF 7100
(used) 1747-aic Allen-Bradley/1747aic
ALLEN BRADLEY 1494V-H9 (Surplus New not in factory packaging)
ALLEN BRADLEY 100S-C09DJ14BC (Surplus New not in factory packaging)
ALLEN BRADLEY 855E-B24TA3 (Brand New Current Factory Packaging)
ALLEN BRADLEY 50387 MODULATOR LOGIC BOARD 118387
Allen Bradley SLC 500 13-Slot Rack, 1746-A13, SER-B, 30 day warranty
ALLEN BRADLEY MOTOR PROTECTOR 1406-G SER. A *USED*
ALLEN BRADLEY 1492-HWACAB070Y (Surplus New In factory packaging)
ALLEN BRADLEY 700-NT200A1 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 1492-HWACAB070WB (Surplus New In factory packaging)
ALLEN BRADLEY 1492-IFM40F-2 (Surplus New not in factory packaging)
ALLEN BRADLEY 1734-OB4 1734OB4 90207 ! NEW !
ALLEN BRADLEY 1734-IB4 1734IB4 130650 ! NEW !
ALLEN BRADLEY M00564733 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 1771-ARC (Used, Cleaned, Tested 2 year warranty)
Allen Bradley AB 1771-P7 Series D AC Power Supply Used
Allen Bradley Z11013 NSFP **GENUINE** AB Z 11013
ALLEN BRADLEY 802M-CY16 (Brand New Current Factory Packaging)
Allen Bradley X110387 NSFP **GENUINE** AB X 110387
Allen Bradley X215808 NSFP **GENUINE** AB X 215808
ALLEN BRADLEY 140U-KTD3-D30 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 802T-CMN (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 2094-PR1 (Brand New Current Factory Packaging)
Allen Bradley2A01 NSNP **GENUINE** AB2 A01
ALLEN BRADLEY 140U-I6C3-C30-M (Surplus New not in factory packaging)
ALLEN BRADLEY 50905-001 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 1494D-N30 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 1494U-H9 (Surplus New In factory packaging)
ALLEN BRADLEY802M-XZJ7 (Surplus New In factory packaging)
ALLEN BRADLEY 700DC-R440Z2 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 634978-90 (Used, Cleaned, Tested 2 year warranty)
Allen Bradley 2364SPE57ANSFP **GENUINE** AB 2364 SPE57A
ALLEN BRADLEY 2801-NC6-15METER (Used, Cleaned, Tested 2 year warranty)
Allen Bradley79A06 NSFP **GENUINE** AB79 A06
ALLEN BRADLEY872C-DH2NP12-E2 SERIES A *NEW IN FACTORY BAG*
ALLEN BRADLEY 190S-DNDJ2-CC16C(Surplus New not in factory packaging)
ALLEN BRADLEY 42GRF-9103 SER.A *USED*
ALLEN BRADLEY 700-C111A24 (Surplus New In factory packaging)
ALLEN BRADLEY 40021-503-02 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 20AD-DB1-C (Surplus New In factory packaging)
ALLEN BRADLEY3A16 (Surplus New not in factory packaging)
ALLEN BRADLEY 140U-JTH3-D25 (Surplus New In factory packaging)
ALLEN BRADLEY 709-BAB43 (Surplus New In factory packaging)
ALLEN BRADLEY 802T-WSPJ1 SERIES J *USED*
Allen Bradley 1492CB3G200 NSFP **GENUINE** AB 1492 CB3 G200
ALLEN BRADLEY GB4001959 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 700DC-N700Z2 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 855T-B24GL3 (Brand New Current Factory Packaging)
Allen Bradley69A06 NSFP **GENUINE** AB69 A06
ALLEN BRADLEY 1756-IV16 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 1333-CAB SER. C ADJUSTABLEFREQUENCY DRIVE(AS IS) *USED*
ALLEN BRADLEY 2755-NB1 (Surplus New In factory packaging)
ALLEN BRADLEY 709-BJD (Used, Cleaned, Tested 2 year warranty)
Allen Bradley 1492CB2F400 NSFP **GENUINE** AB 1492 CB2 F400
ALLEN BRADLEY 1492-SP3C010-N (Surplus New In factory packaging)
ALLEN BRADLEY 845H-SJHZ25-CMY2 (Used, Cleaned, Tested 2 year warranty)
Allen Bradley70A06 NSFP **GENUINE** AB70 A06
ALLEN BRADLEY 845H-SJHZ14CJY1 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 836T-T253JX40S60 (Surplus New In factory packaging)
ALLEN BRADLEY 193-EA1EB (Surplus New In factory packaging)
ALLEN BRADLEY 1770-TB HAND GELD TERMINAL BASER *USED*
ALLEN BRADLEY 845H-SJHZ24CMY2 (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 897H-G232 (Surplus New In factory packaging)
ALLEN BRADLEY 1775-RM (Used, Cleaned, Tested 2 year warranty)
ALLEN BRADLEY 193-EA1CC (Surplus New In factory packaging)
