Re: [CAD_CAM_EDM_DRO] Resettable Fuses

A mechanical switch in the line can blow the drivers because the abrupt
transition to open circuit can result in some pretty huge back EMF
voltages. PPTC devices switch relatively slowly so they would not cause
a problem. However there is no real point in fitting an overcurrent
device on a stepper. No matter how you load the stepper the driver will
regulate the current to keep it within safe limits. The only time such a
device could protect the motor is if the driver fails and shorts the
power supply directly to the motor. This failure mode is fairly rare. A
fuse on the input line would protect the motor just as well.

If a drive fails and it has no supply fuse it can end up so badly
damaged it is not repairable. If you have a fuse in the input line it
won't stop the drive failing but it will limit the damage so the drive
will probably be repairable. Note if you are using Gecko drives and
fuse the supply you must fit an extra capacitor as close to the drive as
possible, even if the leads are short.

Les

wanliker@... wrote:

>I believe the main consequence will be blown drivers.
>
>This of course would depend on the brand of drivers, and what there design
>is.
>A properly designed driver will control the current.
>Opening a motor lead, while under operating conditions, can let the Magic
>Smoke out.
>
>If I am wrong, I am sure someone will correct me.
>bill
>
>
>