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This might be a stupid question but, what limits the heat power output of a heating resistor? Is it the temperature that the material can handle, or does the electrical power itself cause a heater to fail?

I'm using polyimide heaters for a project, and I've seen different product descriptions specify power and voltages, but then datasheets only mention typical values and no specific. I can't seem to find answers to my question.

Since they're just resistors my feeling is, I can increase the voltage/power and as long as it stays in it's operating temperature it will be fine (at least until the voltage is so high it starts to spark?). Is that correct?

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  • \$\begingroup\$ Your second question is a bit troubling - the electrical power is the source of the heating that causes the temperature rise. \$\endgroup\$ – mike65535 Dec 4 '18 at 13:03
  • \$\begingroup\$ Link to datasheet? \$\endgroup\$ – Misunderstood Dec 5 '18 at 9:53
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Since they're just resistors my feeling is, I can increase the voltage/power and as long as it stays in it's operating temperature it will be fine (at least until the voltage is so high it starts to spark?). Is that correct?

Nearly right - you also have to consider the peak current limitations of the element and its feed wires etc.. If you drove the element with DC then you wouldn't have to worry about current; just power. However if you use a high current value for a short duration to give a moderate power (as in PWM systems) then you can still damage the device through an over-current situation rather than on total watts of heat dissipation.

Consider this transistor's (NJVMJD45H11) safe operating area graph (just a clear example of what is called the safe operating area): -

enter image description here

As you can see there is a thermal limit (overall power dissipation) but there's also a wire-bond limit and that is the thing that defines the maximum current. Of course there's also the voltage limit as alluded to in the question.

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  • \$\begingroup\$ This is what I was looking for thank you. With regards to wire bond vs thermal limit, isn't the wire bond issue just another thermal issue? Is this specifically relating to semi conductors? I'm not sure I understand how current itself can cause damage to something like a resistor \$\endgroup\$ – Gordon13 Dec 5 '18 at 15:19
  • \$\begingroup\$ Without knowing the precise details of the device I cannot say whether there is a wire bond limit. Wire bond fusing is a recongnized cause of failure in semiconductors over and above the thermal heat issue and associated problems with junction temperature being exceeded. Many simpler devices will not have a wire bond issue of course but some will. \$\endgroup\$ – Andy aka Dec 5 '18 at 17:36
  • \$\begingroup\$ The kind of device I am using is this heater. \$\endgroup\$ – Gordon13 Dec 6 '18 at 10:23
  • \$\begingroup\$ Does it have a data sheet or something that shows the safe operating area? \$\endgroup\$ – Andy aka Dec 6 '18 at 11:10
  • \$\begingroup\$ Here's the datasheet but it doesn't really show an operating area. \$\endgroup\$ – Gordon13 Dec 6 '18 at 12:11

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