With the acquisition of Powersim by Altair and the transition of the PSIM software into the Altair product offering, we are not offering a demo version of PSIM anymore.
As an industrial customer, you can request a free trial of the PSIM professional edition for your evaluation purposes
As a student, you can request the free Student Editon bundle (includes a nearly full-featured PSIM license).
As faculty, you can request the Academic Edition bundle