Rectifier specification
Required DC current
—A
Max DC voltage
—V DC
Peak power draw
—kW
Transformer rating
—kVA
Enter values above to see the recommended rectifier spec.
⚠ Hard anodizing — specify ripple ≤ 5 % and ensure the rectifier can ramp from 12 V to your max voltage in a controlled, programmable ramp (0.5–2 V/min). IGBT units are strongly preferred.
⚠ Chromic acid anodizing — REACH/RoHS compliance required for Cr(VI). Voltage is low (20–40 V) but the bath is highly corrosive; specify stainless steel current connections and lead-lined or PP-lined tank.
Process reference — current density & voltage ranges
| Process |
CD (A/dm²) |
Voltage (V DC) |
Bath temp (°C) |
Ripple max |
Rectifier type |
| Type II sulphuric (decorative) |
1.2 – 1.8 |
15 – 20 |
18 – 22 |
10 % |
Thyristor or IGBT |
| Type III hard anodizing |
2.5 – 3.5 |
20 – 80 (ramping) |
−2 to +2 |
5 % (pref. 2 %) |
IGBT with ramp |
| Type I chromic acid |
0.3 – 0.5 |
20 – 40 |
35 – 40 |
5 % |
Thyristor or IGBT |
| Structural / architectural (thick) |
1.5 – 2.0 |
18 – 25 |
18 – 22 |
10 % |
Thyristor or IGBT |
Formula used
The calculator follows these steps:
Base current (A) = work area (dm²) × CD (A/dm²)
Rated current (A) = base current × safety margin
Peak power (kW) = rated current × max voltage / 1 000
Transformer kVA = peak power (kW) / power factor
Standard rectifier sizes in India
Indian rectifier manufacturers (Voltas, Statcon, Techno Power, Transrectifier) typically offer standard current ratings at: 500 A, 750 A, 1 000 A, 1 500 A, 2 000 A, 3 000 A, 5 000 A. The calculator rounds your rated current up to the next standard size.
Bus bar and cable sizing
Copper bus bars are sized at 1 A per mm² of cross-section for continuous duty. For a 2 000 A line, that means 2 000 mm² — typically 4 × 500 mm² flat bars. Aluminium bus bars need 1.6× the cross-section of copper for the same current rating. Include bus bar resistance in your voltage margin — a 6-metre run at 2 000 A can drop 2–3 V.
Frequently asked questions
How do I calculate the rectifier size for my anodizing tank?
Multiply your total work area (dm²) by the current density for your process. Add a 20–25% safety margin for jig resistance, bus bar losses, and future capacity. For voltage, Type II needs 15–20 V; hard anodizing needs 20–80 V. Divide the resulting wattage by the power factor (0.85 for thyristor, 0.92 for IGBT) to get the transformer kVA.
Should I use IGBT or thyristor rectifiers for anodizing?
IGBT rectifiers give lower ripple (<2%), faster ramp control, and better efficiency — they are preferred for hard anodizing where ripple above 5% degrades coating hardness and causes striations. Thyristor (SCR) rectifiers are lower capital cost and adequate for decorative Type II sulphuric work. IGBT units typically cost 15–25% more than thyristor equivalents of the same rating.
What ripple percentage is acceptable for hard anodizing?
The industry rule of thumb for hard anodizing (Type III) is ripple ≤5%; aerospace and defence work per MIL-A-8625 Type III recommends ≤2%. High ripple causes micro-porosity at grain boundaries and reduces coating hardness. For decorative Type II work, ≤10% is generally acceptable.
How much does an anodizing rectifier cost in India?
In India, thyristor rectifiers for decorative anodizing cost approximately ₹1,200–2,000 per amp for 500–3,000 A units. IGBT rectifiers with programmable ramp control cost ₹2,500–4,000 per amp. A complete 2,000 A / 24 V thyristor unit with transformer typically costs ₹28–40 lakh installed, including electrical panel and copper bus bars. See our
equipment sourcing guide for vetted Indian suppliers.
What voltage rating should I specify for hard anodizing?
Hard anodizing voltage rises as the oxide layer builds resistance. A 6061 alloy part anodized to 50 µm typically reaches 40–60 V by end of cycle; high-silicon alloys (4xxx series) can reach 80+ V. Specify your rectifier to at least the peak voltage expected for your alloy and target thickness, with 10–15% headroom. Under-voltage at end of cycle results in soft, thin coatings.