Engineering · Electrical & Control
Electrical Control Panel Architecture
What goes where in a control panel, and why?
A good panel is a hierarchy: power comes in through an isolator and protection, is split into branches, and a separate low-voltage control system tells the loads what to do. Power, control and signal wiring are kept apart, everything is bonded to one earth, and the heat is taken out. This page lets you click through the layout, switch the power, 24 V, signal, safety and network layers on and off, size the incoming breaker and 24 V supply, count I/O with spare capacity, check wiring clearances and size the cooling.
Select a part. The order from top to bottom follows the power: entry and protection, then control and drives, then terminals and earth, then cable entry. Real layouts change with the panel size and the machine.
Switch layers on and off to follow one flow at a time. Safety signals go to the drive STO or the contactors on their own path, not through the normal PLC output.
A first estimate from the connected power, using the combined efficiency and power factor you enter. Cable size, short-circuit rating, discrimination between breakers and the motor starting current must be checked from the maker’s data and the standard.
Spare capacity is easiest to add now. Typical advice is 20 to 30 per cent spare I/O, spare terminals and spare space on the rail and in the duct.
| Component | What it does | Selection and placement note |
|---|
Typical industry clearances for parallel runs. Cross different groups at 90 degrees. Use separate ducts, or one duct with a continuous divider with no gaps. Confirm against IEC 60204-1 or the standard your site follows and the drive maker’s manual.
| Wire use | Typical colour (IEC 60204-1 practice) |
|---|
Bond all metal parts to the PE busbar by the shortest path, keep the earth strap to the mounting plate short, and terminate shields over 360 degrees. Follow the drive maker’s manual for the motor cable shield.
A rough estimate: a painted sheet-steel enclosure loses about 5.5 W per square metre per kelvin through its surface, and a fan needs about 3.1 m³/h per watt per kelvin. The temperature limit of the hottest device decides the allowed rise. Use the enclosure and fan makers’ data for the final selection.
Values are typical and indicative. The calculators are for a first estimate and not for the final design. Panels must be built and tested to the standard that applies (for machines IEC 60204-1, for assemblies IEC 61439-1) by a competent person. Isolate and lock out before working inside a panel.