Impact of AC effects on current density analysis of pcb for 50-60Hz

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Discussion Overview

The discussion centers on the current density analysis of a PCB designed for distributing AC power at 50-60Hz. Participants explore the implications of AC effects on current density compared to DC analysis, particularly in the context of low-frequency applications and the associated electromagnetic losses.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that current density analysis typically refers to DC IR drop, which does not account for AC effects, suggesting the need for AC impedance analysis to evaluate EM losses.
  • Another participant agrees that at 50-60Hz, AC behavior should not deviate significantly from DC for reasonably sized PCBs, questioning the necessity of distributing AC mains frequencies on a PCB.
  • A participant emphasizes that the skin depth in copper at 50/60Hz is much greater than the trace width, implying that AC effects can be largely ignored in this frequency range.
  • Concerns are raised about ensuring sufficient copper section to handle the required current and the potential for surface insulation breakdown between tracks, which may necessitate design modifications.

Areas of Agreement / Disagreement

Participants generally agree that AC effects at 50-60Hz can be considered negligible for current density analysis in typical PCB designs, but there are varying opinions on the implications of safety regulations and design considerations for AC mains applications.

Contextual Notes

Participants mention the importance of safety agency approvals and design rules, indicating that there may be specific regulatory considerations that are not fully explored in the discussion.

Who May Find This Useful

Engineers and designers working on PCB layouts for AC power distribution, particularly those involved in low-frequency applications and safety compliance.

ursonor99
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TL;DR
what is the correct approach to current density analysis of a PCB when it is distributing 50-60 hz AC power
Hello ,
I was looking into current density analysis of a PCB that handles distribution of AC power . from ansys and cadence sites , i realized by current density they refer to DC IR drop that is a pure ohmic analysis that doesn't take into consideration the AC effects . And in order to take this into consideration , we need to go to AC impedance analysis and obtain EM losses . But I observed this kind of analysis was done for high frequency AC circuits for decoupling cap suggestions etc .

So i was curious to know how much the current density behavior will deviate from DC for a low frequency like 50-60Hz ? as for such frequencies the skin depths are much greater than trace width and thickness
 
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Welcome to PF.

Your instincts are good; 50-60Hz AC should not deviate much from DC for reasonable size PCBs. Is this for a power supply PCBA? Why are you needing to distribute AC Mains frequencies on a PCB? What kind of currents and voltages are involved? Are you well-versed in safety agency AC Mains design rules?
 
berkeman said:
Welcome to PF.

Your instincts are good; 50-60Hz AC should not deviate much from DC for reasonable size PCBs. Is this for a power supply PCBA? Why are you needing to distribute AC Mains frequencies on a PCB? What kind of currents and voltages are involved? Are you well-versed in safety agency AC Mains design rules?
The voltages are 208VAC 4W . the pcb takes AC mains power and generates few DC voltages and also powers few AC motors etc .
 
The traces on a circuit board are thin compared to skin depth in copper at 50/60 Hz. For that reason AC effects can be ignored. The tracks will be wide, so will have lower inductance. Avoid multi-layers as I²R heat needs to escape.

One problem will be having enough copper section to carry the required current.
Another problem will be surface insulation breakdown between tracks or surface terminals, that may require slots be cut in the PCB.
 
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ursonor99 said:
The voltages are 208VAC 4W . the pcb takes AC mains power and generates few DC voltages and also powers few AC motors etc .
With my Mentor superpowers, I can see what country you are posting from. What safety agency approvals will you be applying for with this new product?
 
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