VPI SDS use question

I recently made several upgrades to my Scoutmaster and now have an SDS. I've got everything set up and running, but just had a question about the operation of the SDS. When the SDS is on, but the table is off, the voltage is steady at 72. When I turned the table on and set it to 33 RPM, the voltage jumps to 84. Changing to 45 RPM makes the voltage increase to 102. I just wanted to make sure this was normal operation as I'm not familiar with the SDS and the manual (like most VPI manuals) isn't very clear.