Zana ya Uhandisi Isiyolipisha
Kikokoteni cha Mtandao wa Nyota-Delta
Linganisha uanzishaji wa DOL dhidi ya Star-Delta (Y-Δ) wa mota. Kokotoa mikondo ya kuanza, nguvu za kuzunguka, ukubwa wa kontakta, na muda wa kubadilisha.
Matokeo ya Ulinganisho
Kanuni ya Uanzishaji wa Star-Delta
Katika uanzishaji wa Y-Δ, mzunguko wa mota unaunganishwa kwanza katika umbo la nyota (Y), ukipunguza volteji kwenye kila mzunguko hadi VL/√3. Baada ya mota kufikia kasi ya ~80%, inabadilishwa kwenda delta (Δ) kwa uendeshaji wa volteji kamili.
Both current and torque are reduced by a factor of 3 (not √3). This is because the winding voltage is reduced by √3, and both current and torque scale with voltage².
Ukubwa wa Kontakta
- KM1 (Kuu/Mstari) — Hubeba mkondo kamili wa mstari; panga ukubwa kulingana na mkondo wa kawaida
- KM2 (Delta) — Carries phase current = line current / √3 ≈ 58% of rated
- KM3 (Star) — Hubeba mkondo wa nyota = mkondo wa mstari / √3 ≈ 33% ya kawaida
Mwongozo wa Muda wa Kubadili
The timer for star-to-delta transition should be set so the motor reaches approximately 75–85% of rated speed before switching. Too early = high transition current spike. Too late = motor overheats in star.
| Motor Power | Kipima Muda Kinachopendekezwa | Notes |
|---|---|---|
| Up to 7.5 kW | 3–5 seconds | Injini ndogo zinaharakisha haraka |
| 7.5–30 kW | 5–10 seconds | Injini za kati, za kawaida za viwandani |
| 30–90 kW | 8–15 seconds | Injini kubwa, zenye msongo mkubwa zaidi |
| >90 kW | 10–20 seconds | Injini kubwa sana, rekebisha kwa kufuatilia mkondo |
Ulinganisho: Mbinu za Kuanza
| Method | Mkondo wa Kuanza | Torque ya Kuanza | Cost | Best For |
|---|---|---|---|---|
| DOL | 6–8× In | 1.5–2.5× Tn | Low | Injini ndogo <7.5 kW |
| Star-Delta | 2–3× In | 0.5–0.8× Tn | Medium | Injini za kati, mzigo mwepesi wa kuanza |
| Soft Starter | 2–4× In | 0.5–1.5× Tn | Medium-High | Kuanza kwa ulaini, pampu, conveyor |
| VFD | 1–1.5× In | 1.5× Tn | High | Kasi inayobadilika, kuokoa nishati |
| Autotransformer | 1.5–4× In | Adjustable | Medium-High | Mizigo yenye msongo mkubwa, vipigo vinavyoweza kurekebishwa |
⚠️ Important: Kuanza kwa nyota-delta kunafanya kazi tu kwa injini zilizoundwa kwa uendeshaji wa delta kwa voltage ya mstari (mf., 400V Δ / 690V Y). Bamba la injini lazima lionyeshe tathmini ya voltage mbili. Y-Δ hupunguza torque ya kuanza kwa ÷3, ambayo inaweza kutosheleza kwa mizigo yenye msongo mkubwa.
Mfano wa Vitendo
Given: 22 kW, 400V, In = 42A, starting multiplier = 7×
DOL starting current = 42 × 7 = 294 A
Y-Δ starting current = 294 / 3 = 98 A
Torque ya kuanza ya DOL = 1.5× Tn
Torque ya kuanza ya Y-Δ = 0.5× Tn — inafaa kwa pampu za centrifugal/mashabehe, inaweza kushindwa kwa conveyor zenye mzigo
Gundua matatizo ya kuanza kwa motor na matatizo ya mtetemo kwa kutumia vifaa vya kitaalamu.
