Transformer A loading
80%
Calculateur de mise en parallèle de transformateurs
Vérifiez si deux transformateurs peuvent fonctionner en parallèle (groupe vectoriel, rapport, impédance, rapport de puissance) et visualisez comment la charge se répartit entre eux en proportion inverse de leur impédance de court-circuit.
Résultat
Saisissez votre charge → obtenez une conception complète & une nomenclature en quelques secondes
Exemple de résultatParallel load sharing
798 / 502 kVA
1300 kVA total across 1000 kVA (uk 6%) + 630 kVA (uk 6%) · Feasible for parallel operation ✓
Transformer B loading
80%
Combined capacity
1630 kVA
Overall load factor
80%
Parallel-operation conditions (IEC 60076)
| Condition | Value | Verdict |
|---|---|---|
| Same vector group | Matched (e.g. Dyn11 = Dyn11) | PASS ✓ |
| Same voltage ratio | 0% difference (≤ 0.5% recommended) | PASS ✓ |
| Impedance within tolerance | |uk_A − uk_B| = 0.0% of mean (≤ 10%) | PASS ✓ |
| Capacity ratio ≤ 3:1 | 1.59 : 1 | PASS ✓ |
Load sharing calculation
| Weight A | Sa ÷ uk_A = 1000 ÷ 6 = 166.7 |
| Weight B | Sb ÷ uk_B = 630 ÷ 6 = 105.0 |
| Load A | 1300 × 166.7 ÷ 271.7 = 798 kVA (80%) |
| Load B | 1300 × 105.0 ÷ 271.7 = 502 kVA (80%) |
Conclusion
The two units can operate in parallel; load splits in inverse proportion to their short-circuit impedance.
Bill of materials
| Equipment | Spec | Qty | Subtotal |
|---|---|---|---|
| Transformer A (oil-immersed S11) | 1000 kVA · uk 6% | 1 | POA |
| Transformer B (oil-immersed S11) | 630 kVA · uk 6% | 1 | POA |
| Total equipment | POA |
Pour les ingénieurs de réseaux électriques et d'usines dimensionnant des parcs de transformateurs en parallèle pour la redondance, l'extension de capacité ou la fiabilité N−1.
Utiliser le calculateur
Exemple concret
Un exemple de référence pré-calculé (indexable — aucun JavaScript requis). Saisissez vos propres paramètres ci-dessus pour un résultat en direct.
Exemple 1 — 1000 kVA + 630 kVA, impédance appariée à 6 %
Parallel load sharing
798 / 502 kVA
1300 kVA total across 1000 kVA (uk 6%) + 630 kVA (uk 6%) · Feasible for parallel operation ✓
Transformer A loading
80%
Transformer B loading
80%
Combined capacity
1630 kVA
Overall load factor
80%
Parallel-operation conditions (IEC 60076)
| Condition | Value | Verdict |
|---|---|---|
| Same vector group | Matched (e.g. Dyn11 = Dyn11) | PASS ✓ |
| Same voltage ratio | 0% difference (≤ 0.5% recommended) | PASS ✓ |
| Impedance within tolerance | |uk_A − uk_B| = 0.0% of mean (≤ 10%) | PASS ✓ |
| Capacity ratio ≤ 3:1 | 1.59 : 1 | PASS ✓ |
Load sharing calculation
| Weight A | Sa ÷ uk_A = 1000 ÷ 6 = 166.7 |
| Weight B | Sb ÷ uk_B = 630 ÷ 6 = 105.0 |
| Load A | 1300 × 166.7 ÷ 271.7 = 798 kVA (80%) |
| Load B | 1300 × 105.0 ÷ 271.7 = 502 kVA (80%) |
Conclusion
The two units can operate in parallel; load splits in inverse proportion to their short-circuit impedance.
Bill of materials
| Equipment | Spec | Qty | Subtotal |
|---|---|---|---|
| Transformer A (oil-immersed S11) | 1000 kVA · uk 6% | 1 | POA |
| Transformer B (oil-immersed S11) | 630 kVA · uk 6% | 1 | POA |
| Total equipment | POA |
Exemple 2 — impédance et rapport désadaptés
Parallel load sharing
883 / 417 kVA
1300 kVA total across 1000 kVA (uk 6%) + 630 kVA (uk 8%) · Not recommended — check conditions below ✗
Transformer A loading
88%
Transformer B loading
66%
Combined capacity
1630 kVA
Overall load factor
80%
Parallel-operation conditions (IEC 60076)
| Condition | Value | Verdict |
|---|---|---|
| Same vector group | Matched (e.g. Dyn11 = Dyn11) | PASS ✓ |
| Same voltage ratio | 1.5% difference (≤ 0.5% recommended) | FAIL ✗ |
| Impedance within tolerance | |uk_A − uk_B| = 28.6% of mean (≤ 10%) | FAIL ✗ |
| Capacity ratio ≤ 3:1 | 1.59 : 1 | PASS ✓ |
Load sharing calculation
| Weight A | Sa ÷ uk_A = 1000 ÷ 6 = 166.7 |
| Weight B | Sb ÷ uk_B = 630 ÷ 8 = 78.8 |
| Load A | 1300 × 166.7 ÷ 245.4 = 883 kVA (88%) |
| Load B | 1300 × 78.8 ÷ 245.4 = 417 kVA (66%) |
Circulating current
A 1.5% no-load ratio difference drives a circulating current of ≈ 80 kVA between the two units (adds to the load, does not supply the load).
Bill of materials
| Equipment | Spec | Qty | Subtotal |
|---|---|---|---|
| Transformer A (oil-immersed S11) | 1000 kVA · uk 6% | 1 | POA |
| Transformer B (oil-immersed S11) | 630 kVA · uk 8% | 1 | POA |
| Total equipment | POA |
Comment il a été calculé
- · Poids de répartition de charge : w = S_nom ÷ uk pour chaque unité.
- · Charge de l'unité A : S_A = S × w_A ÷ (w_A + w_B) ; idem pour l'unité B.
- · Taux de charge : S_A ÷ S_nom,A (doit rester ≤ 100 %).
- · Conditions de parallèle : même groupe vectoriel, même rapport de tension (≤0,5 %), impédances à ±10 % l'une de l'autre, rapport de puissance ≤ 3:1.
- · Courant de circulation (désadaptation de rapport) : I_c ≈ ΔU ÷ (Z_A + Z_B) en per-unit.
Normes référencées
| Standard | Scope |
|---|---|
| IEC 60076-1 | Transformateurs de puissance — exigences générales |
| IEC 60076-8 | Transformateurs de puissance — guide d'application |
| IEEE C57.12.00 | Norme pour les exigences générales des transformateurs de distribution et de puissance immergés dans un liquide |
Questions fréquentes
What conditions must transformers meet to run in parallel?
Per IEC 60076, parallel transformers must match: voltage ratio (within ~0.5%), Vector Group, impedance voltage uk (within ~10%), and preferably power rating ratio under 3:1. Mismatched vector groups cause circulating current and severe overheating. The calculator checks these conditions and reports pass/fail.
How is load shared between parallel transformers?
Load shares inversely with impedance: the Transformer with lower uk carries more load. Two transformers of equal rating with uk 6% and 4.5% split load in the ratio 4.5:6, so the 4.5% unit carries 57%. The calculator computes the load share by impedance and flags overloading.
Why run transformers in parallel?
Parallel operation provides redundancy (one can be taken out for maintenance without outage), allows capacity to be added incrementally, and can improve efficiency at light load by running only one unit. The trade-off is higher fault level at the bus. The calculator models the parallel arrangement and its Fault Current.
What is circulating current between parallel transformers?
Circulating current flows when parallel transformers have unequal voltage ratios or different vector groups, even with no load, causing extra losses and heating. A 1% ratio mismatch can drive 5-10% circulating current. IEC 60076 limits the ratio difference to ~0.5%. The calculator checks for this.
What fault level results from paralleling transformers?
Paralleling transformers roughly sums their short-circuit contributions. Two 1000 kVA, 6% uk transformers give ~48 kA at the LV bus versus ~24 kA for one, so the switchgear must be uprated. The calculator computes the combined fault level so you can check panel ratings.
Intégrer ce calculateur
Ajoutez ce calculateur à votre propre site web gratuitement. L'iframe s'adapte à toute largeur et s'exécute entièrement dans le navigateur de votre visiteur.
Outils associés
SelectionCalculateur de sélection de transformateurVerificationCalculateur de court-circuitSelectionDécodeur de modèle de transformateur
Les résultats sont des estimations d'ingénierie pour la conception préliminaire et à titre de référence uniquement. Vérifiez toujours avec les normes applicables, la plaque signalétique de l'équipement et un ingénieur agréé avant l'achat ou l'installation.
Send my complete design report
Get the full bill of materials, single-line diagram, calculation steps and FOB pricing as a PDF — free, no sign-up.
Your data stays private. No spam — only a reply to your enquiry.