Тема: БЛОК ПИТАНИЯ МОДУЛЬНЫЙ или НЕМОДУЛЬНЫЙ?

Навіщо цифри брати зі стелі? Є стандарт АТХ, там все розписано для відповідних конфігурацій за потужністю, [Только для зарегистрированных пользователей. Зарегистрироваться.]
ні про які 40 А там і мови не може бути на групу провідників.

На групу провідників max 240 VA.

Multiple +12 V Rails

As power supply capacity increased, the ATX power supply standard was amended (beginning with version 2.0[3]) to include:


3.2.4. Power Limit / Hazardous Energy Levels
Under normal or overload conditions, no output shall continuously provide more than 240 VA under any conditions of load including output short circuit, per the requirement of UL 1950/​CSA 950/​EN 60950/​IEC 950.

—ATX12V Power Supply Design Guide, version 2.2[4]

This is a safety limit on the amount of power that may pass, in case of a fault, through any one wire. That much power can significantly overheat a wire, and would be more likely to melt the insulation and possibly start a fire.

Ideally, there would be one current limit per wire, but that would be prohibitively expensive. Since the limit is far larger than the reasonable current draw through a single wire, manufacturers typically group several wires together and apply the current limit to the entire group. Obviously, if the group is limited to 240 VA, so is each wire in it. Typically, a power supply will guarantee at least 17 A at 12 V by having a current limit of 18.5 A, plus or minus 8%. Thus, it is guaranteed to supply at least 17 A, and guaranteed to cut off before 20 A.