Using 240Vdc Rated MOV Motor Operated Valve on 262-270Vdc Battery System

Our operating voltage here is typically around 262Vdc and is on a battery system. Therfore, from time to time we equalize (charge) our batteries which causes our DC plant volatge to increase to around 270. We are having trouble finding a direct replacement for our MOV due to our voltage requirements. The closest MOV repalcement we have found is rated for 240Vdc with a voltage tolerance of 10%. I could install a resistor in series with the H-bridge motor circuit to cause a voltage drop, but then I would be effecting the operating characteristics of the motor. Is there any solutions where I could make this 240Vdc MOV work?

JohnA quick check on Digikey ( https://www.digikey.ca/products/en/circuit-protection/tvs-varistors-movs/141?k=MOV ) shows Varistors/MOVs all the way up to several thousand volts.  There are several in voltages close to your requirement.

MOV - motor operated valve(Actuator)

If these motors are driven by an H-bridge, does the control system do proportional control?  If so, I wonder of you could limit the output duty cycle so a 240 volt motor would work.
How big are these motors?  How much current bare we talking about here?Would it be an option to add a DC-DC converter between the batteries and the H-bridge to reduce the voltage?I know- that's more questions than answers at this point, but if you give us more info we'll try to help with a solution.-Rick

John...at a guess your MOV would not take much current?  And it sounds like your input voltage is always over 260V?  If so there are plenty of transistors with VCEO > 300V - I came across the BDY93 the other day which is 350V.  You could make a simple voltage dropper circuit (basically a Zener and an emitter follower, though you'd probably want to build in things like short circuit protection, etc) that would drop  an input of (say) 255 - 275 volts down to a steady 240V.  Your Zener would have to be a string of smaller Zeners , or you'd do it with an opamp control circuit - i daresay you could do something with the good old 723 IC -  but it's not an impossible ask.