Gunner Asch wrote:

Ive got a 5hp PC3 vfd running my Gorton MasterMill.
The top end voltage it is supposed to run on..is 230vts + about 5 volts
It will run down to 200 volts.
Im running it on single phase, been doing it for years.

Now the power company has increased my 220 single phase to about 249
volts and when I try to start it..I keep getting OverVoltage Alarm.

Well, the real problem here is the VFD has a VERY restricted operating
range. It must have been designed for 208 V only +/- a percentage.

249 V is not unusual in many places.

I cant get the power company to change the tap down to a normal voltage,
let alone 220 volts

How do I (cheaply) transform high voltage down 14-29 volts ac?
What you need is a transformer with 240 V primary and 12 - 15 V secondary
with 10 A output rating. You wire the primary across the mains, and put
the secondary in series with one of the mains wires going to the VFD.
Check the output first with the VFD disconnected. One polarity will
increase the voltage, the other will drop it by the secondary voltage
rating.

Now, if you can't find such a transformer with a 240 V primary, you could
rig up a 120 V primary transformer between one hot and the neutral to do
the same thing. The only problem is you may not have run a neutral to a
purely 240 V load. The 120 V to 12.6 V filament transformer should be
fairly easy to come by.

There are also "voltage adjusting" transformers that have multiple taps in
small steps and 240/208 autotransformers, often found in buildings with
120/208 power and 230 V window airconditioners.

Jon