浮吊變幅、抓斗和提頭機(jī)構(gòu)拖動負(fù)載屬于位能型負(fù)載,各機(jī)構(gòu)運(yùn)行時,在抱閘線圈松開的一瞬間,或者在低速啟動的過程中,如果電機(jī)由于電磁慣性一時不能建立足夠的磁場強(qiáng)度或者低速力矩特性太差不能提供足夠的力矩,則都會發(fā)生抓斗下溜現(xiàn)象。變頻器閉環(huán)矢量控制能提供快速力矩響應(yīng),低速力矩特性好,對于兩種‘溜鉤’原因都有良好的克服效果,在重鋼浮吊控制中基本沒有觀察到‘溜鉤’現(xiàn)象。如果勵磁慣性太大而仍有溜鉤發(fā)生,則可以通過特殊控制加以克服。
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在浮吊電氣控制系統(tǒng)中,變幅機(jī)構(gòu)、抓斗機(jī)構(gòu)和提頭機(jī)構(gòu)采用閉環(huán)矢量控制,其低速力矩性能可防止負(fù)載下溜,其很硬的機(jī)械特性則可使各運(yùn)行機(jī)構(gòu)嚴(yán)格按操作人員發(fā)出的指令運(yùn)行。浮吊旋轉(zhuǎn)機(jī)構(gòu)是雙電機(jī)驅(qū)動,要求運(yùn)行同步,且難以實現(xiàn)脫開負(fù)載的自學(xué)習(xí),因此不具備矢量控制的條件,故作者設(shè)計采用一臺變頻器驅(qū)動兩臺電機(jī),變頻器采用開環(huán)v/f控制模式,調(diào)試時采取了低速電壓補(bǔ)償,實踐證明這種設(shè)計是合理的,使用效果很好。
浮吊控制系統(tǒng)中,抓斗和提頭兩股鋼繩的受力平衡是比較難解決的問題,在原繞線電機(jī)串電阻調(diào)速驅(qū)動、繼電器—接觸器控制系統(tǒng)中,只有靠時間繼電器的延時配合機(jī)械特性較軟的電機(jī)調(diào)速控制特性來實現(xiàn),效果很差。安川的616g5變頻器具有力矩控制和速度控制切換功能,利用這一功能特點(diǎn),在浮吊抓斗和提頭運(yùn)行機(jī)構(gòu)間采用力矩跟蹤控制模式,再利用plc的靈活控制性能,很好地攻破了這一技術(shù)難關(guān)。
3 變頻改造中應(yīng)注意的幾個問題
由于浮吊控制系統(tǒng)的復(fù)雜性和所處環(huán)境的特殊性,在浮吊電氣控制系統(tǒng)調(diào)試過程中,遇到了很多問題,總結(jié)如下:
Instrument Transformers Inc 2RL-151 Current Transformer, 150:5 Ratio, 600V
RIBXGTA Solid State Contact Current Sensor SPST: 30 Vac/dc, 0.4 amp max O41
New Veris Hawkeye 735 Solid-Core Current Switch w/ Command Relay 24VAC/DC
Banner CI3RC MAXI-AMP Current Trip Point Amplifier
ABB TCSGAB AC Current Sensor 2-20A 3-50VDC
Crouzet 84 871 009 Current Control Relay 120V~50/60Hz
Crouzet DIART-110VAC Current Control Relay 24VDC w/Crouzet TI-100
SENTRY SC250 Current Switch 1-135V (AC/DC), 0.3A MAX, 1.5-150A Range
Crouzet DIAR.T-110VAC Current Control Relay
LEM HAL50-S Current Transducer (-)150A to (+)150A
Kasuga CT-051A Current Transformer 600V
Pepperl+Fuchs Current Separator KFDX-DCV
RF Technologies Current Switch 1.5-150A CS1150A-LED
Sentry 250 Current Switch 250Amp
New Omron E39-F32D Stainless Protective Spiral Tube 1 Meter Long
Keyence FS-V31P Fiber Optic Amplifier, PNP, 1 Output, 640nm, 12-24VDC
Banner SM312FQD MINI-BEAM Fiber Optic Sensor 10-30VDC w/2 SS Fiber Cables
Bannner D10DPFPQ Fiber Optic Sensor, 12-24VDC, 2 PNP, Quick Disconnect
New Omron E3X-MDA6 Digital Fiber Sensor Photoelectric Switch NPN 12-24VDC
New Omron E3X-MDA41 Digital Fiber Sensor Photoelectric Switch PNP 12-24VDC
New Omron E3X-DA11AN-S Digital Fiber Sensor Photoelectric Switch NPN 12-24VDC
New Omron E3X-DA21-S Digital Fiber Sensor Photoelectric Switch NPN 12-24VDC
New Omron E3X-DA6-S Digital Fiber Sensor Photoelectric Switch NPN 12-24VDC
Keyence FS-V31 Fiber Optic Amplifier, NPN, 1 Output, 640nm, 12-24VDC
New Banner D10DNFP Fiber Optic Sensor, 12-24VDC, 2 NPN, 30FT Cable
Banner D10DPFP Plastic Fiber Optic Sensor, 12-24VDC, 2 PNP
New Banner PIT46UMFR Plastic, Opposed Mode Fiber Optic, 1mm Core, Threaded
New Banner PIA26U Plastic, Opposed Mode Fiber Optic, 0.5mm Core, Angle
New Banner PIAT46UM.4X.4MT Plastic, Opposed Mode Fiber Optic, 1mm Core, AngleCP40
CP40B
P0914XB
IPM2-P0904HA
P0960HA
07KT97
07KT98(WT98)
9662-610
9662-610
9753-110
AIP502
CP30B
CP40
FBI10E
AMM12C
AMM42T
CP345
MRI-234*B
NFCP100-S00
PW401
RB401
SR750 750-P5-G5-D5-HI-A20-R-E
New Banner PIA16U Plastic, Opposed Mode Fiber Optic Cable, 0.25mm Core, Angled
New Banner PBP16U Plastic, Diffuse Reflective Fiber Optic Cable, 0.25mm Core
Keyence FS-V11 Hybrid Fiberoptic Sensors NPN Output 12 to 24VDC 50mA 12" Length
New Banner Q45BB6 Fiber Optic Sensor 4 wire, 10 to 30VDC with 30' Cable
Banner IAT11S Terminated Single Fiber Sensor, 12" with right-angle threaded end
Banner BMAP.753P Bifurcated Plastic Fiber Optic Cable