About the ACDB Sizing
AC Distribution Board (ACDB) sizing determines the rating of AC busbars, MCBs or MCCBs, surge protection devices, and metering components on the inverter's AC output side — between the inverter and the grid connection point or plant transformer.
How to calculate it
- 1Calculate inverter AC output current: I = P_inverter ÷ (√3 × V_line × PF) for 3-phase; I = P ÷ (V × PF) for single-phase.
- 2ACDB busbar rating: ≥ total AC output current × 1.25.
- 3Each inverter gets an MCCB or MCB on the ACDB input, rated for the inverter's maximum AC output current × 1.25.
- 4Add Type II AC SPD (40–60 kA) on the ACDB output busbar.
- 5Include energy meter (class 0.5 or 1.0) for net metering or plant monitoring.
- 6Ensure ACDB main breaker rating ≤ transformer HV winding's thermal limit.
Worked example
A 100 kW inverter at 415 V, 3-phase, 0.98 PF. Output current = 100,000 ÷ (1.732 × 415 × 0.98) = 141.8 A. ACDB busbar: 180 A. MCCB for this inverter: 160 A. AC SPD: 40 kA Type II. Energy meter: class 1.0 bidirectional (for net metering export recording).
What you can calculate
- Type B RCCB
- 4-pole isolator
- AC busbar
- CEA 2010
Frequently asked questions
Is a separate ACDB needed for every inverter?
Not necessarily. Multiple inverters of the same rating are often connected to a shared ACDB with one MCCB per inverter — the ACDB then feeds a plant-level AC panel or transformer. The shared ACDB must be rated for the combined output of all inverters connected to it.
What is the difference between ACDB and the main LT panel?
The ACDB is a solar-specific panel for the inverter AC outputs — it aggregates inverter outputs and connects to the main LT (low-tension) switchboard or transformer LV panel. The main LT panel is a facility-level board managing all loads, grid import, and solar import together. They are separate boards: the ACDB feeds into the LT panel, not the other way around.
Ready to build your solar project?
Get free quotes from verified EPCs and installers across India.
You might also need
DC Cable Sizing
Size DC string and main cables per IEC 60364-7-712 & CEA standards with temperature and installation derating
OpenAC Cable Sizing
Size AC cables from inverter to grid per IS 732 & IEC 60364 with full load current derating and voltage drop
OpenVoltage Drop
Calculate voltage drop % for DC and AC circuits and verify compliance with IEC & IS limits across the system
OpenShort Circuit Current
Calculate maximum DC and AC short-circuit current at each system point for protection device sizing
OpenFuse / MCB / MCCB Sizing
Select correct fuse rating, MCB curve, and MCCB interrupt capacity for DC strings, combiners, and AC outputs
OpenCombiner Box (AJB) Sizing
Size Array Junction Boxes with string count, fuse ratings, SPD specification, and busbar current capacity
Open