I have a 3 phase zero fire SCR/SSR set that has 480V input. I put my Fluke 289 (which is a tRMS meter) across the different phases on the load side. Then adjusted the output. The voltage read ~470V from 0 to full output. I also switched my Meter to measure frequency and it read 59Hz regardless of the SCR output. Is this the result I should expect or is something wrong?