Which model?
Xigmatek X-Calibre series 500W (XCP-A500)
NRP-PC series 500W (NRP-PC501)
NRP-PC series 500W (NRP-PC502)
Tauro series 500W (XTK-TB-0500A(B))
Xigmatek NRP-VC series 500W (NRP-VC503)
The NRP-VC503 will die in a shower of sparks when you attempt to draw its labelled power capacity.