Do ta lêy hö sè cña my biðn dßng bng 1 nªn gi

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Do ta lÊy hÖ sè cña m¸y biÐn dßng b»ng 1 nªn gi¸ trÞ dßng ®iÖn ®Çu ra cña m¸y biÕn dßng ®iÖn l μ 5,77 A. Chän ®iÖn trë ®Çu ra cña biÕn dßng l μ 1 Ω . Chän hÖ sè bé biÕn ®æi dßng ¸p l μ 1 nªn ta cã ®iÖn ¸p ë ®Çu ra cña bé biÕn ®æi ®iÖn ¸p l μ 5,77 V. §iÖn ¸p ra cña bé biÕn ®æi dßng ¸p ® îc cung cÊp trùc tiÕp cho bé biÕn ®æi / abc αβ l μ 5,77 V. Do bé biÕn ®æi / abc αβ chØ biÕn ®æi trôc to¹ ®é m μ kh«ng biÕn ®æi gi¸ trÞ biªn ®é ®iÖn ¸p nªn gi¸ trÞ ®iÖn ¸p cña ®Çu ra αβ còng cã gi¸ trÞ l μ 5,77 V. Chän ®iÖn trë R1= 0,331 k Ω . Khi ®ã ®iÖn trë R2 cã gi¸ trÞ R2 = 5,77 - 0,331 = 5,439 k Ω Khi chän xong gi¸ trÞ ®iÖn trë ta tiÕn h μ nh thay gi¸ trÞ ®iÖn trë v μ ch¹y m« pháng.
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§å ¸n tèt nghiÖp ThiÕt kÕ bé nghÞch l u PWM 5kW Ho μ ng Ngäc Tu©n líp TB§1 - K46 §¹i häc B¸ch khoa H μ Néi 130 KÕt qu¶ ch¹y m« pháng Chän thêi gian b¾t ®Çu håi tiÕp tÝn hiÖu l μ 0,02s. Ta cã kÕt qu¶ nh sau: H×nh 4.35: §å thÞ dßng ®iÖn ra khi cã håi tiÕp ë tÇn sè 500 Hz B»ng hç trî cña PESIM ta ®o ® îc biªn ®é dßng ®iÖn ra khi cã håi tiÕp dßng ®iÖn: I max = 8,20 V Gi¸ trÞ hiÖu dông dßng ®iÖn ra: I = 8,20 2 = 5,79 A Sai lÖch dßng ®iÒu khiÓn: 5,79 5,77 % .100% 5,77 I Δ = = 0,34 % Thay ®æi tÇn sè ta cã c¸c gi¸ trÞ dßng ®iÖn ®Çu ra. Khi tÇn s« nghÞch l u l μ 400 Hz. H×nh 4.36: §é thÞ dßng ®iÖn khi tÇn sè 400 Hz
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§å ¸n tèt nghiÖp ThiÕt kÕ bé nghÞch l u PWM 5kW Ho μ ng Ngäc Tu©n líp TB§1 - K46 §¹i häc B¸ch khoa H μ Néi 131 B»ng phÐp ®o ta cã biªn ®é dßng ®iÖn ®Çu ra: I max = 8,19 A Gi¸ trÞ hiÖu dông dßng ®iÖn ®Çu ra: I = 8,19 2 = 5,78 A Sai sè dßng ®iÖn ®iÒu chØnh: 5,78 5,77 % .100% 5,77 I Δ = = 0,17 % Khi tÇn sè nghÞch l u 300 Hz, 200 Hz, 100 Hz ta m« pháng t ¬ng tù v μ sai sè lu«n n»m d íi 2%. Khi tÇn sè l μ 50 Hz H×nh 4.37: §å thÞ dßng ®iÖn khi tÇn sè 50 Hz Biªn ®é dßng ®iÖn ®Çu ra: I max = 8,46 A Gi¸ trÞ hiÖu dông cña dßng ®iÖn ®Çu ra: I = 8,46 2 = 5,98 A Sai sè dßng ®iÖn ®iÒu khiÓn: 5,98 5,77 % .100% 5,77 I Δ = = 3,64 % Khi tÇn sè 10 Hz
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§å ¸n tèt nghiÖp ThiÕt kÕ bé nghÞch l u PWM 5kW Ho μ ng Ngäc Tu©n líp TB§1 - K46 §¹i häc B¸ch khoa H μ Néi 132 H×nh 4.38: §å thÞ dßng ®iÖn khi tÇn sè 10 Hz Ta thÊy do bé håi tiÕp dßng ®iÖn nªn dßng ®iÖn ®Çu ra bÞ giíi h¹n trªn. Gi¸ trÞ cùc ®¹i cña dßng ®iÖn ®o ® îc: I max = 8,29 A Gi¸ trÞ hiÖu dông cña dßng ®iÖn: I = 8,29 2 = 5,86 A Sai sè dßng ®iÖn ®iÒu khiÓn: 5,86 5,77 % .100% 5,77 I Δ = = 1,56 % KÕt kuËn: Tõ c¸c thèng kª ë c¸c d¶i tÇn sè vËn h μ nh cña bé nghÞch l u ta thÊy r»ng: NÕu lÊy sai sè ®iÒu khiÓn dßng ®iÖn l μ 5% th× m¹ch ph¶n håi dßng ®iÖn ®¸p øng ® îc yªu cÇu ®iÒu chØnh dßng ®iÖn t¶i tr íc sù thay ®æi cña tÇn sè ®Çu ra cña bé nghÞch l u.
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