240V-120V transformer heats up device?

Question

HiI live in Europe and have a network router that operates powered by apower supply (transformer of 240VAC->5VDC)I bought the exact same  router from US and plugged its power supply(transformer of 120VAC->5VDC) on a 240VAC->120VAC transformer.I notice that the US transformer heats up more than the european one.It is more hot that the 240VAC->120VAC transformer.Can anyone explain as to why this is happening?Does it have anything to do with the frequency in the US being 60HZ asopposed to here being 50HZ?Note that the US power supply is attached onto the transformer , andso some of the heat is transferred from the transformer to the powersupply.

John Larkin · Accepted Answer

50 Hz supply will push cheap 60 Hz transformers somewhat intosaturation, and increase losses.John

Tom Biasi · Answer

Just buy the euro power supply for that router.

Phil Allison · Answer

"interuser"

** It is solely due to that fact.

120 volt primary transformers made for the US domestic market are simply not designed to operate at 50 Hz. Making them do so by using a 230/120 step-down transformer causes them to run hotter - sometimes MUCH hotter and this can lead to failure of the transformer's insulation or the activation of an internal thermal fuse.

Other problems include buzzing or humming noises emanating form the transformer or nearby metal panels.

Toroidal transformers intended for 120 volt@ 60 Hz are most likely to be in serious overload if ever operated at 50 Hz - even with no load applied to the secondary.

...... Phil

240V->120V transformer heats up device?

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