To convert the percentage of Obasi's overtime earnings to a fraction of his regular hourly wage, we start with the given information that he earns \(150%\) of his regular hourly wage while working overtime.
We can express \(150%\) as a fraction:
\[ 150% = \frac{150}{100} \]
We simplify this fraction:
\[ \frac{150}{100} = \frac{3}{2} \]
This means that while working overtime, Obasi earns \(\frac{3}{2}\) of his regular hourly wage.
To find out what fraction of his regular hourly wage he earns while working overtime, we can express \(\frac{3}{2}\) relative to his regular hourly wage:
- Let \(W\) represent his regular hourly wage.
- During overtime, he earns \(\frac{3}{2}W\).
Thus, while working overtime, Obasi earns:
\[ \frac{\frac{3}{2}W}{W} = \frac{3}{2}. \]
Therefore, the fraction of his regular hourly wage that Obasi earns while working overtime is:
\[ \boxed{\frac{3}{2}}. \]