It won't stop if it's ventilated with outdoor ambient air:
40C air can hold 51 g of water per m3 of air. 60C air can hold 130 g of water per m3 of air [1]. The curve is exponential.
So, it works as long as the transformer is hotter than ambient air, even at the most humidest (100% RH). The transformer's heat will drop the relative humidity of the air near its surface, and the heated air can absorb more water again.
If the humidity is below 100% RH, what changes is that the evaporating water could cool it to below ambient air temperature, same effect as in swamp coolers.
It won't stop if it's ventilated with outdoor ambient air:
40C air can hold 51 g of water per m3 of air. 60C air can hold 130 g of water per m3 of air [1]. The curve is exponential.
So, it works as long as the transformer is hotter than ambient air, even at the most humidest (100% RH). The transformer's heat will drop the relative humidity of the air near its surface, and the heated air can absorb more water again.
If the humidity is below 100% RH, what changes is that the evaporating water could cool it to below ambient air temperature, same effect as in swamp coolers.
[1] https://www.engineeringtoolbox.com/maximum-moisture-content-...