While I was sorting things out with my set-up I used grease that was too heavy, To trouble shoot, you can eliminate the step-down voltage drop quite easily. Try that and see if the speed remains constant. Then you can try the different drop down steps until the speed becomes unstable. For instance 72 volts is too low for 45 RPM but it works fine at 84V. Basically, I agree with Marc51 above on reading his post more closely.
VPI SDS speed issue
I am having trouble with a consistent speed on my Aries 2 two pulley setup. I find I have to at times set the frequency to almost 66 to get it spot on. At other times it may be at 63. I read somewhere about the voltage preset may need adjusting. How is that done or is there something else I should be looking to adjust? The motor stas at 115, shifts to about 84after warm And then maysettle down to about 72 Hz. Any help?