Denford Triac Spindle Issue

[m_c]

It sounds like there is some kind of isolation issue with the drive speed control.

If the drive speed control is being connected to ground, then that can cause an RCD to trip.
The speed control circuit on these kind of drives sits around half of mains voltage, so if you connect it to 0V/GND (the control electronics will typically tie 0V to GND), then you've just created an earth leakage which an RCD will detect, but as it'll be pretty low current, it may not always be enough current to trip the RCD.

I wonder if the isolation on the controller has failed.
A manual fix, would be to install a potentiometer to control the spindle speed. There is a slim possibility that I may still have a suitable potentiometer kicking around the workshop, but I won't have any time to look until next week, as I'm working at an event all weekend.

[John11668]

It sounds like there is some kind of isolation issue with the drive speed control.


I wonder if the isolation on the controller has failed.
A manual fix, would be to install a potentiometer to control the spindle speed. There is a slim possibility that I may still have a suitable potentiometer kicking around the workshop, but I won't have any time to look until next week, as I'm working at an event all weekend.

From what I can see sprint 1200 is a non isolated drive .
I am told that a potentiometer should control speed even directly connected but it will be supplying an input at the mid point of 170v or so. if you want to send signals from the computer there has to be an intervening board .

[m_c]

From what I can see sprint 1200 is a non isolated drive .
I am told that a potentiometer should control speed even directly connected but it will be supplying an input at the mid point of 170v or so. if you want to send signals from the computer there has to be an intervening board .

There is an intervening board. The Baldor controller that Denford fit to their machines.
However I'm not sure if the Baldor controller does the isolation, if there is a separate isolated supply for the Baldor controller specifically for the speed control, or if the analogue speed control is done by a totally separate board.
There is also the added complication that this machine has been upgraded from it's original serial controller to a USB controller, so I don't know how much may have been changed from the wiring diagrams that are available on the Denford forums.

I know KB drives of that era often had an option for isolated inputs, but I don't think Sprint did.


GingerNinja, have you traced where the 54/55 wires go to? Do they connect to the controller, or do they connect to the drive rack?