---
title: "Anodizing Calculator — Rectifier Sizing (DC, kVA) India"
description: >-
  Free anodizing calculator: enter tank area + process type, get required DC current (A), voltage (V), and transformer kVA. Built by a live plant operator in India.
canonical: "https://www.saravanaconsultancy.in/calculators/rectifier-sizing"
source_url:
  html: "https://www.saravanaconsultancy.in/calculators/rectifier-sizing"
  md: "https://www.saravanaconsultancy.in/calculators/rectifier-sizing.md"
last_modified: 2026-05-24
---

Free Calculator

# Anodizing Rectifier Sizing Calculator

Enter your tank work area and process type to get required DC current, voltage range, transformer kVA, and a recommended rectifier specification. Covers Type II sulphuric, Type III hard anodizing, and chromic anodizing.

## Inputs

Process type

Type II — sulphuric anodizing (decorative)
Type III — hard anodizing
Type I — chromic acid anodizing
Custom — enter CD and voltage manually

Total work area (dm²)

Sum of all part surface areas loaded at once (both sides)

Current density (A/dm²)

Type II typical: 1.2 – 1.8 A/dm²

Max operating voltage (V)

Type II: 15–20 V  ·  Hard anodizing: up to 60–80 V

Safety margin (%)

20 % — standard
25 % — recommended
30 % — large multi-jig lines

Accounts for jig resistance, bus bar losses, future capacity

Power factor

0.85 — thyristor rectifier
0.92 — IGBT rectifier
0.95 — modern IGBT with PFC

## 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.

### Need a full rectifier specification for procurement?

We prepare detailed rectifier datasheets, vendor shortlists from vetted Indian and imported suppliers, and factory acceptance test (FAT) criteria. Part of our [equipment sourcing service](/buy/anodizing-equipment).

[Talk to an expert](/contact)
[Equipment sourcing guide →](/buy/anodizing-equipment)

## 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](/buy/anodizing-equipment) 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.