Quote Originally Posted by Jonathan View Post
If the spindle is stalled and drawing rated, or even higher, current from the VFD, that's actually requires very little power from the mains. One way to think of it is to recall that power is the product of torque and speed, so when the spindle is stalled the speed is zero so the mechanical power required to apply rated (or any) torque is also zero. From an electrical point of view, you still have to put current through the winding to get torque, but that current in this situation is only supplying the losses in the motor ... so the power, and thus current, drawn from the supply is low - I'd guess an amp or two at most.
Ok well I'm not arguing here as I'll bow to your superior knowledge of electronics but what your saying if I drive the spindle into the bed it won't pull any more amps cos it's not spinning.? So why does the VFD have current limit setting and trip when spindle embeds it's self into material.? Surely that power that trips the VFD is being pulled form some where.?