# Power Nets

This constraint aims to establish the minimum trace widths needed to prevent excessive resistive heating on traces carrying high currents, and to allow the user to specify which nets should have power pours.

### Automatic Detection

Nets with certain attributes will be automatically classified as high current nets. This will include:

* Any net that matches our various patterns for being a voltage or power net.
* Any net in a "Power" netclass.

### Recommended Patterns

You can force Quilter to detect a power net by placing it in a "Power" net class. This is particularly helpful for nets that do not have a voltage-pattern name (like 3V3) but do need to carry a significant amount of current, such as a net that powers a motor.

### Defaults

We assign conservative default values to every automatically detected net, assuming they are unlikely to carry high current. If a net is expected to encounter a substantial amount of current, you should specify the maximum in the interface.

Nets with detected voltages under 3V are assigned a 200mA maximum current by default, and nets over 3V receive a maximum of 500mA.

### Constraint details

<figure><img src="/files/sGkkGoPT1Juit762P0YC" alt=""><figcaption></figcaption></figure>

Power nets can be set up in the "Power Nets" section of Circuit Comprehension. You can add them one by one, match them with regex, or use a netclass.&#x20;

To define a power net constraint, you'll need to fill in the following fields:

1. Net name
2. Maximum current (mA)
3. Optionally choose if you want that net to be a power pour

Quilter automatically completes IPC calculations that consider the specified copper weight and layer thickness for each stack-up to determine the ideal trace width for the net to prevent overheating.

### Physics Rule Checks

The PRCs that validate this constraint after compilation are:

**Overheated Length** determines the approximate analytic temperature rise of trace segments on a specified high current nets. A net segment is considered “overheated” if its approximated temperature rise exceeds 20C.


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