How to Choose the Right Control Transformer for Your Panel Board

Why Control Transformers Matter

Control transformers step down the supply voltage (typically 415V or 440V) to a safe control circuit voltage (24V, 48V, or 110V) for operating relays, contactors, PLCs, and HMI panels.

Selecting the Right VA Rating

The VA (Volt-Ampere) rating determines how much load the transformer can handle:

• 40-100 VA — Small panels with a few relays and indicators
• 150-300 VA — Medium panels with PLC, HMI, and multiple contactors
• 500-1000 VA — Large panels with multiple drives and heavy control loads
• 1000+ VA — Complex automation systems with multiple sub-panels

Rule of thumb: Add up all control circuit loads and multiply by 1.25 for safety margin.

Insulation Class

• Class F (155°C) — Standard for most industrial applications
• Class H (180°C) — For high-temperature environments or continuous heavy loads

Custom Options from Sri Vaarii

We build transformers with any VA rating and custom primary/secondary voltage taps. No minimum order quantity — even a single custom unit is welcome. Typical delivery: 24-48 hours.