Two things leap out at me: Your generator has some very serious regulation problems, and may be undersized, and your Astron power supply must not have the correct fuse installed. If the MOV fires, the fuse is sized to blow instantly. That said, Astron has been known to install MOVs that have a wide tolerance, and those near the low end may go into avalanche mode at only a few volts above nominal 120 VAC. The national standard for nominal utilization voltage is 120 +/- 5%. That means the utility can supply anything between 114 and 126 VAC and be within the required tolerance. 126 VAC is darned close to 130 VAC, and that MOV is already getting hot!
73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of AA8K73 GMail Sent: Monday, June 07, 2010 6:47 PM To: [email protected] Subject: Re: [Repeater-Builder] MOVs for power supply primary I added a 130 Volt MOV across the hot and neutral of an Astron 50 Amp power supply for a repeater and had an interesting effect. We lost AC power and switched over to the generator. When the load was added to the generator, the Onan's voltage sagged a bit and the throttle opened to bring the speed back. It overshot slightly and was high enough to trip the MOV. That short slowed the generator down until the voltage was too low and then the generator sped up again. And again it fired the MOV and slowed down until it cleared. It kept oscillating with huge voltage swings until I unplugged the Astron power supply. Sigh. kq7dx wrote: > > > Hello to group, > Is putting a MOV from hot to ground, neutral to ground, on the primary > of the transformer of the power supply a good idea.. > I have a ICE surge suppressor on in front as well but thought I would > put more inside the supply for back up. > > Also, are the MOVs that radio shack sell any good. Rated at 130VAC. Any > body used them... > > Last question: when MOVs fail or take a surge do they fail in a shorted > condition taking out the fuse till the MOV can be replaced, or do they > blow or fail open leaving the supply working. > > Thanks for the help.. > 73s
