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docs: "The same or a different kind?" of ISQ Part 6 extended

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Mateusz Pusz
2024-11-12 09:53:31 +01:00
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docs/blog/posts/isq-part-6-challenges.md
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@ -401,8 +401,8 @@ Some quantities are more complicated than others. For example, _power_ has:
- var (e.g., _reactive power_),
- complex quantities expressed in VA (volt-ampere) (e.g., _complex power_).
How should we model this? Maybe those should be two independent trees of quantities, each having
a different unit?
How should we model this? Maybe those should be two or three independent trees of quantities, each
having its own unit?
```mermaid
flowchart TD
@ -411,14 +411,50 @@ flowchart TD
power --- electromagnetism_power["<b>electromagnetism_power</b> | <b>instantaneous_power</b><br><i>(instantaneous_voltage * instantaneous_electric_current)</i>"]
power --- active_power["<b>active_power</b><br><i>(1 / period * instantaneous_power * time)<br>(re(complex_power))</i>"]
apparent_power["<b>apparent_power</b><br><i>(voltage * electric_current)<br>(mod(complex_power))</i><br>[VA]"]
nonactive_power["<b>nonactive_power</b><br><i>(mass * length<sup>2</sup> / time<sup>3</sup>)</i><br>[VA]"]
nonactive_power --- reactive_power["<b>reactive_power</b><br><i>(im(complex_power))</i><br>[var]"]
complex_power["<b>complex_power</b><br>{complex}<br><i>(voltage_phasor * electric_current_phasor)<br>(active_power + j * reactive_power)</i><br>[VA]"]
complex_power --- apparent_power["<b>apparent_power</b><br><i>(voltage * electric_current)<br>(mod(complex_power))</i>"]
```
This will mean that we will not be able to add or compare _active power_, _reactive power_, and
_apparent power_, which probably makes a lot of sense. However, it also means that the following
will fail to compile:
```cpp
quantity apparent = isq::apparent_power(100 * VA);
quantity active = isq::active_power(60 * W);
quantity<isq::nonactive_power[VA]> q = sqrt(pow<2>(apparent) - pow<2>(active)); // Compile-time error
```
Also the following will not work:
```cpp
quantity active = isq::active_power(60 * W);
quantity reactive = isq::reactive_power(40 * var);
quantity<isq::apparent_power[VA]> q = sqrt(pow<2>(active) + pow<2>(reactive)); // Compile-time error
```
If we want the above to work maybe we need to implement the tree as follows?
```mermaid
flowchart TD
power["<b>power</b><br><i>(mass * length<sup>2</sup> / time<sup>3</sup>)</i><br>[W]"]
power --- mechanical_power["<b>mechanical_power</b><br><i>(scalar_product(force, velocity))</i>"]
power --- electromagnetism_power["<b>electromagnetism_power</b> | <b>instantaneous_power</b><br><i>(instantaneous_voltage * instantaneous_electric_current)</i>"]
power --- apparent_power["<b>apparent_power</b><br><i>(voltage * electric_current)<br>(mod(complex_power))</i><br>[VA]"]
apparent_power --- active_power["<b>active_power</b><br><i>(1 / period * instantaneous_power * time)<br>(re(complex_power))</i>"]
apparent_power --- nonactive_power["<b>nonactive_power</b><br><i>(sqrt(apparent_power<sup>2</sup> - active_power<sup>2</sup>))</i><br>"]
nonactive_power --- reactive_power["<b>reactive_power</b><br><i>(im(complex_power))</i><br>[var]"]
apparent_power --- complex_power["<b>complex_power</b><br>{complex}<br><i>(voltage_phasor * electric_current_phasor)<br>(active_power + j * reactive_power)</i>"]
```
This will mean that we will not be able to add or compare _active power_ with _apparent power_,
which probably makes a lot of sense. Again, ISQ does not provide a direct answer here.
However, the above allows direct addition and comparison of _active power_ and _nonactive power_,
and also will not complain if someone will try to use watt (W) as a unit of _apparent power_ or
_reactive power_.
Again, ISQ does not provide a direct answer here.
## More base quantities?