Should "sine" or "cosine" function be used to represent currents in a 3-ph system?

[powersys]

Should "sine" or "cosine" function be used to represent currents in a 3-ph system?

Assume a balanced three-phase system.
Each phase current contains harmonics: 1st, 5th, 7th, ...
If I would like to write the phase current in an equation form, should "sine" (Case-A) or "cosine" (Case-B) function be used?
Please note that the plot (see below) for i_A written using "sine" function is different from that using "cosine" function.

 

[BradtheRad]

Re: Should "sine" or "cosine" function be used to represent currents in a 3-ph system

Looking where the sine fundamental crosses zero: Notice a similar slope in its harmonics.

This is not the case with the cosine. The 7th harmonic runs crosswise where the fundamental crosses zero.

Picture if you were to apply positive DC to an idle system. During the initial moment, I think all harmonics would start going in the same direction, namely positive.

So it seems to me you should go with the sine function rather than cosine.

 

[permute]

Re: Should "sine" or "cosine" function be used to represent currents in a 3-ph system

IIRC, cosine is more traditional. This is from the phasor representation with e^jw used to represent phase A. real(e^jw) = cosine.

 

[powersys]

Re: Should "sine" or "cosine" function be used to represent currents in a 3-ph system

If 'sine' is used, which case (Case-S or Case-T) is correct?

For example, should the 5th harmonic of phase-B be expressed as "I₅sin[5(ω-2π/3)]" or "I₅sin(5ω - 2π/3)"?

Thanks.