Servo Dynamics 1525 Voltage Regulator

[BulletHead]

My mill has 3 Servo Dynamics 1525-10 drive boards that randomly get voltage errors and shut down. The voltage LED is for overvoltage and undervoltage conditions. After trying high and low input voltages within the specified range I'm suspecting is a momentary overvoltage and the shunt regulator isn't dissipating that excess voltage.

I read this regulator has several resistors behind the capacitor. Mine only has 1 10 ohm resistor rated at 12 watts and holes where more could have been mounted. Does that sound right to you? Is that enough to dissipate the energy put back into the system by several axes in motion and changing direction?

 

[adama]

Does the fuse and resistor measure ok? Is the shunt regulator working? All these bits have a pretty tough high cycle use and hence may fail in time.

Thing to realise, that resistor can dissipate 10 watts constantly, can cope with a lot more than that for the typical short pulse you would see in a axis de-accelerating. If you find its data sheet online it should give you the peak impulse dissipation numbers.

Don't change that resistor to something else till you have found out what the shunt regulator is rated to pass power wise. That is what sets the resistors resistance rating.

 

[gustafson]

Is it happening on decel, or at the end of a rapid?

might look at the connection of that resistor to ground


Or maybe the big storage cap is dying

 

[Bruce Griffing]

My guess is that one or several of your electrolytic capacitors are going South. This is a very common problem with older electronics as wet electrolytic caps have a limited life. A common strategy for restoring old electronics is to replace them all. That is where I would start.

 

[BulletHead]

Does the fuse and resistor measure ok? Is the shunt regulator working? All these bits have a pretty tough high cycle use and hence may fail in time.

The fuses are intact and the resistor is in the 10 ohm range the drive manual specifies. The regulator is keeping the voltage in the proper range but I was thinking there could be some spike that sets off the error that is too quick to detect with my voltage meter.

 

[BulletHead]

Is it happening on decel, or at the end of a rapid?

It seems to happen randomly during a cut. One day I got 150 cycles out of the mill the next I can hardly go 10 cycle without the drive dropping out. It doesn't seem to be related to temperature. Almost never during rapid moves. The X axis does it more sometimes only setting off that drives voltage warning. Other times it sets off the voltage warning on all three cards leading me to think it might be a supply problem.

 

[BulletHead]

My guess is that one or several of your electrolytic capacitors are going South.

This is something I had not considered. Thanks!