Re: [CAD_CAM_EDM_DRO] Servo heat-sensors or paranoia?

R Rogers wrote:

>Have an E-stop and be in close proximity of it at all times. Displays for current draw are not really neccessary. More of a gadget than a vital component. Any halfway decent machine is not going to bind on an axis. In the event of a crash the last thing anyone is going to be doing is checking a readout to confirm its happening. A fuse before the drive should blow before the motor fries.
>

This is not likely to work, until the drive burns out! Due to the
switching action, and the fact that a stalled
motor develops no back EMF, the voltage across the stalled motor is near
zero, therefore the power consumed
is small (voltage x current). While the motor may be getting 20 amps
(at a few volts), the drive will be drawing
just a few amps at the DC supply voltage, so that power in is close to
power out. So, the fuse will have little
current through it, and will NOT blow. (For instance, I test my PWM
servo amps at 20 A into a nearly dead short,
an ammeter shunt. With 30 V in and 20 A out, the amp only draws about 5
A from the power supply.)

Jon