Hero999
Banned
Pommie said:You need a series resistor to provide a holding current.
What do you mean by holding current?
I don't think you've understood how a polyswitch works.
It behaves like a slow blow fuse with a resistor in parallel with it.
There is no need to use a series resistor because the large starting current won't last for long enough to trip it.
However if we limit the current, the voltage will decay to a very low value when the motor is stalled so the power dissipation will be much lower.When a motor is running at max efficiency then the current it draws is the maximum it can draw indefinitely. If we stall the motor then it will not get the cooling effect of the rotating armature and will therefore overheat at that current, hence my suggestion of 75% of the max efficiency current.