The minimum lamp loading of the transformer should be adhered to ensure efficient operation when dimming electronic transformers .It is recommended that electronic dimmable transformers be loaded to at least 70% of their rated maximum wattage.
This is due to the transformers inherent capacitance being increased at low loads, when in series with the dimmer this can reduce the overall capacitance of the circuit which may in turn reduce the stability of dimmer.
As more transformers are added to the circuit this results in a greater phase difference between current and voltage. Too much of a phase difference and the dimmer will lose stability