newbie question about ac motors inverters

[yopp]

Hello everybody, here is my problem: I need to know the value of the root mean square of the current in a mosfet of an inverter for ac motors, like this
https://www.ewh.ieee.org/soc/es/Nov1998/08/PWMINV.HTM

i mean, usually you can express the current with i(t)= Imax*sin(wt) and the Irms is Imax/sqrt2.

But in this case the current is like in the top right diagram (fig pwm4) of the previous link.
So, how can I express the current I(t) and find out the Irms value in the mosfet?

Thanks in advance for the answers