Instruction/ maintenance manual of the product AN-7511 Fairchild
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©2002 Fairch ild Semicond uctor Corpo ration Application No te 7511 Rev. A1 Insulated-Gate Transistors Sim plify AC-Motor Speed Control An IGT’ s f e w input requirements and low On-state resistance simplify driv e circuitry and increase po wer efficie ncy in mo tor- control applications .
©2002 Fairch ild Semicond uctor C orpo ration Application N ote 7511 Rev. A1 F or optically isolated “rela y-action” s witching, it makes sense to replace the phototransis tor optocoupler with an H11L1 Schmitt-trigger optocoupler (Figure 2B).
©2002 Fairch ild Semicond uctor C orpo ration Application N ote 7511 Rev. A1 FI GUR E 5 A. Y IELDING 4-kV ISOLA TI ON, A P IEZOELECTRIC COUPLER P RO VIDES TRANSFO RMER-LIKE PE RFORMANCE AND AN ISOLA TED PO WER SU PPL Y . FIGURE 5B. THIS CIRCUIT PROVIDE S THE DRIVE FOR THIS ARTICLE’S MOTOR-CONTROL CIRCUIT.
©2002 Fairch ild Semicond uctor C orpo ration Application N ote 7511 Rev. A1 A piez oelectric c oupler op erationa lly simila r to a puls e-train dri ve transfor mer, b ut po tent ially less cos tly in hi gh volu me is a sm all, effi cien t device with iso lati on c apabi lit y rang ing to 4kV .
©2002 Fairch ild Semicond uctor C orpo ration Application N ote 7511 Rev. A1 Piezoelec tric Coupler s Pr ovide 4-kV Isolation Using a high-frequen cy oscil lator f or pulse-train driv e Figure 6B yields unlimite d on-time capa bility . Howe ver , the scheme requires an os cillator that can b e turned on a nd off by th e control lo gic.
©2002 Fairch ild Semicond uctor C orpo ration Application N ote 7511 Rev. A1 P o lyphase motors, controlled by solid-state, adjustable-fre- quency ac drives, are used e xtensively in pumps, conv ey ors, mills, machine tools and robotics applications.
©2002 Fairch ild Semicond uctor C orpo ration Application N ote 7511 Rev. A1 It’ s impr actical, ho wev er , to rate an in ve rter based on lock ed- rotor curren t.
©2002 Fairch ild Semicond uctor C orpo ration Application N ote 7511 Rev. A1 Use 6-Step Drive F or Speed-I n variant Tor que Figur e 10A shows th e inver ter c irc uit co nfig ured for th is example. Di odes D 1 thro ugh D 6 ca rry the sam e p eak cur r ent as the IGTs; con sequentl y , they’ re rated to hand le peak cur- rents of a t least 8.
©2002 Fairch ild Semicond uctor C orpo ration Application N ote 7511 Rev. A1 . FIGURE 13A. MOTOR CURRENT AND VOLTAGE ARE SHOWN HERE, FOR LIGHT LOADS FIGURE 13B. MOTOR CURRENT AND VOLTAGE ARE SHOWN HERE, FOR HEAVY LOADS. T o complet e the design of the 6-step moto r drive, it’s necess ary to consider protection circu itry for the ou tput IGT s.
©2002 Fairch ild Semicond uctor C orpo ration Application N ote 7511 Rev. A1 FIGURE 15A. THIS ALL-ENCOMPASSING PROTECTI ON SYSTEM PROVIDES THREE I NDEPENDENT SHUTDOWN FUNCTONS - ONE EACH FOR THE UPPER AND LOWER IGTS AND THE HIGH -VOLTAGE SUPPLY. FIGURE 15B.
©2002 Fairch ild Semicond uctor C orpo ration Application N ote 7511 Rev. A1 Latch-Up: Hints, Kinks and Caveats The IGT is a rugged device , requiring no snubber network when operating w ithin its publishe d safe-oper ating-area (SOA) r atings. Within the SO A, the gate emitter voltage controls the collector current.
©2002 Fairch ild Semicond uctor C orpo ration Application N ote 7511 Rev. A1 FIGURE 17. USE THIS LATCHING-CURRENT TESTE R TO TEST IGTS NONDESTRUCTIVELY. Q 1 ’S BASE-DRIV E PULSE WIDTH IS GREAT- ER THAN THAT OF THE IGT’S GATE DRIVE, SO THE IGT UNDER TEST IS S WITCHED THROUGH Q 1 WHEN REVERSE-BIAS LATCH-UP OCCURS.
DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO A NY PRODUCTS HEREIN TO IMPROVE RELIABILITY , FUNCTION OR DESIGN.
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