On Monday, 20 July 2020 09:03:05 UTC+1, Chris Green wrote:
tabbypurr wrote:
On Sunday, 19 July 2020 23:17:07 UTC+1, Mike McLeod wrote:
On Sun, 19 Jul 2020 21:58:31 +0100, Chris Holford
wrote:

Although the inductance is probably not enough to worry about, the cold
resistance of the element will be less than the resistance at operating
temperature. This means that the initial current at switch-on will be
higher than the normal operating current.

Yup, I was aware of that and measured the current draw under warmed-up
running conditions.

what you need to know is cold resistance.

As I've said above the cold resistance will be very close to the hot
resistance, it's not being heated up to thousands of degrees like an
incandescent bulb. Anyway the element will be made of resistance wire
which will have a very small change of resistance with temperature.

Yup. But from the triac's POV, cold R is what matters. Apply 330v to that R to work out the peak i the triac sees - it will not be 0.35A for a 0.35A blanket.


NT