Quote:
Originally Posted by David Simpson
There shouldn't be any significant "inrush" of current. I assume that the T/F is being used for some vintage radio pursuit. I.e. a resistive load, as opposed to a motor ? Many vintage valve radios only draw 200 to 300mA from the mains, so a 1A fuse is what I fit. That wee T/F is only rated at 50VA, so if it starts to draw 1A, 2A or near to 3A(approx. 750VA at mains voltage) - it'll seriously overheat. What is it being used for ?
Regards, David
|
I disagree.... the peak inrush is determined purely by how saturated the TX core gets if switch on occurs at the worst point in the mains cycle relative to any remanent flux, the resistance of the primary winding and the primary inductance assuming a saturated core. Whilst a small TX will have much lower absolute inrush than a large one, relative to FLC it will still be "large". TX inrush current looks like exponentially decaying huge initial current spikes on top of the primary current waveform and can vary from almost nothing to hundreds of times FLC in the first cycle, depending on timing.
Motor inrush is a different beast related to stall current and how long the motor takes to run up to speed on top of any short term core saturation effects.