Varistors MOV can I change the values ?
I have lots of 250 volt MOV's can I series or parallel connect them like resistors to get a different switch on voltage
I don't think so ... but it just in case
Answer:
No, parallelling MOVs only multiples the energy absorbtion capability, and series-connecting them would tend to let you use a string of low-voltage ones in a higher-voltage circuit, tho I don't think that's a good idea.
MOVs are protective devices that have a high resistance below their rated voltage, but their resistance decreases above that voltage. Their primary application is circuit spike protection/absorbtion.
If you use these 250V MOVs in your presumably-120V application, you will be providing some protection. If you repost or email me the MOV part number you have and also either the part number of the 150V MOV called for or the normal AC voltage of your circuit, I can give you a better idea as to whether the 250s will be proper or not.
You cannot change their value.
However you may be able to use them. It depends on what your trying to protect. I designed a product a few years ago which ran off of 115VAC. The voltage to the equipment could be 230 or 460 volts. The transformers were always jumpered for 230V/115V but could be rewired for 460V/115V. Too often 460 would be applied to the product with the transformer wired for 230. The result was that 230V would come out of the transformer and blow the tar out of the MOV. I changed the MOV to 250V and the MOV would not pop but the fuse on the transformer would blow instead when a coil was energized. The coil was more forgiving and the customer would see the error of his ways and change the wiring and only replace the fuse. The 250 V MOV protected the electronics as well as the 130V. As a result we had happy customers and less blown electronic modules.
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