Using brushless DC servo amp with brushed motor?

Hi Guys,
On Saturday night my mill packed in again. I had problems with the Y-axis Brushed DC motor before and cleaning the carbon from the motor fixed that problem.
Last night, mid cut, the machine tripped out with a servo disconnect alarm and I have been unable to get it running again.
When switching on the servo circuit, the machine will hum for a second while the fault light on the Y-axis servo comes on, and then it trips again with the same fault. Removing the servo motor confirmed that the axis moves freely, and applying 12Vdc to the motor confirms it also runs smoothly.
When I switch the drive cards between axis, the error follows the y-axis servo amplifier.

The fact that I was working at 23:30 on Saturday night should confirm the convenience of this little breakdown

I will take the drive card to someone tomorrow to see if they can repair it, but I need to also get some sort of replacement(s) to ensure I do not get stuck up this creek again.

Browsing around brought me to Advanced Motion Controls B25A20 brush-less servo amp that can drive both Brush-less and brushed motors.
Question is: can most "brush-less" servo amps be used on "brushed" motors?
How do you calculate the size of the brush-less drive to drive a brushed motor?
What would be the make/ models to watch out for?
I see a lot more Brush-less drives floating around on eBay and if usable, I should be able to replace all 3 drives with newer tech drives.

The old drives are Anilam drives that was only sold in the UK, not the Westinghouse drives that was common in the US.
Control is a Anilam Crusader GXM.
Motors are SEM DC servo motors rated at 140V and 58A pulse current, 3000RPM max.

All the electronics on this machine are getting very long in the tooth, hence the reluctance to splash out on new drives. Ideal would be to get it running for another year or so, and then replacing with a much newer machine with tool changer, faster spindle etc. If the control packs in, I might be forced to retrofit, making an upgrade to newer drives worth the cost/ effort.

Opinions and advice much appreciated.

The amc B25A20 is very easy to work with but you have to know how to adjust the pots and tune a drive.
This is maybe not so simple. Not quite enough power for a 58amp peak motor.
B25A20AC is the same amp with an ac/dc bridge in the box which can be tossed.
Maybe a B40A20 or just a straightforward 50A20. First number is the peak amps, second number is the voltage.
B is brushless but you can jumper this out. No letter is DC brush.
50A20s which would be the best fit and the next step up 100A40s are rare ducks on the surplus market.
Then one assumes analog input, not PWM.
This is not a easy swap unless you know servo amps, their flavors and settings.
Tach loop?
I'd have to say I'd tell most to not try this at home as it gets confusing fast.

You do know along with the 4 main brushes, there’s another 4 brushes in the tach if thats what that setup has? The anilam crusader retrofit on by Bridgeport had tachs, if its the same kinda setup there on the motor under the end plates, will need little more than cleaning up, just like the motors.

As far as most people and techs need concern em selves a tach is just a dc motor being ran as a generator, exact same guts - principals and faults. If the motor needed carbon dust cleaned from it, good chance the tach wants the same!

adama said:

You do know along with the 4 main brushes, there’s another 4 brushes in the tach if thats what that setup has? The anilam crusader retrofit on by Bridgeport had tachs, if its the same kinda setup there on the motor under the end plates, will need little more than cleaning up, just like the motors.

As far as most people and techs need concern em selves a tach is just a dc motor being ran as a generator, exact same guts - principals and faults. If the motor needed carbon dust cleaned from it, good chance the tach wants the same!

Click to expand...

Yes, I cleaned he tachs out as well first time round.

CarbideBob said:

The amc B25A20 is very easy to work with but you have to know how to adjust the pots and tune a drive.
This is maybe not so simple. Not quite enough power for a 58amp peak motor.
B25A20AC is the same amp with an ac/dc bridge in the box which can be tossed.
Maybe a B40A20 or just a straightforward 50A20. First number is the peak amps, second number is the voltage.
B is brushless but you can jumper this out. No letter is DC brush.
50A20s which would be the best fit and the next step up 100A40s are rare ducks on the surplus market.
Then one assumes analog input, not PWM.
This is not a easy swap unless you know servo amps, their flavors and settings.
Tach loop?
I'd have to say I'd tell most to not try this at home as it gets confusing fast.

Click to expand...

Thank you for the information Bob.
I need to get this mill running again and sooner is better.
Are there better options out there, should I look at replacing motors as well, or should I prepare for the whole lot?
As stated before, 1. I need this mill to make a living, 2. I see it being replaced in the not too distant future. 3. I do not want to over capitalize on it.
If you reckon there is a good chance of getting it running with one of said replacement drives, I am prepared to give it a go.
Edit - Tach loop, Yes the old setup uses a tach generator to give velocity feedback to the amp. Control gives +-10v analog signal to the servo amp and pulse encoders give feedback to the control.
I do have the tuning procedure for the existing amplifiers.

I just got hold of the guys who built those drives 27 odd years ago and they still offer a replacement drive that looks almost exactly as it did then.
Waiting on price from them, but I think it might be best to just plug one of those suckers in and get on with life?? technology looks old, but I guess so is all the other links in this chain?

My drives are 2120/A2 ,
and here is a link to the replacement:http://www.kdpes.co.uk/?wpdmdl=48

As well as cleaning the tachs and motors out did you under cut the insulation bettwen the rotor segments? that does not apply to all tachs - motors, but if it wears slow enough it can raise the brushes up.

I got around the whole crusader issues by simply retrofitiing it with linux cnc and geko drives, all the mechanicals + motors are there, all i did was strip out the old control, stick a break out board in the old control box along with 2 geko drives. Got rid off all the old annilam drives, but used there power supply. Took the tachs out of the motors, returned the shaft ends and fitted 200 line quad encoders. Not a fix for you this week, but if you work out all the bits you need ahead of time its not that much work to do i did it in a fortnight of evenings.

adama said:

I got around the whole crusader issues by simply retrofitiing it with linux cnc and geko drives,

Click to expand...

Are you a home shop?

New replacement drive is USD460 Sounds like a lot for such an old card, but maybe worth it for the plug-it-in-and-get-on-with-life aspect of it.
I have nothing against the linux CNC idea, but the Geko drives sounds a bit "light"???
I should still be able to use the Anilam (Norwin) drives if I do a retrofit?

Regards
Pieter

I used to have that same machine and the same problems... plus they constantly whined a high pitch noise that drove me crazy. They are pretty bullet proof and generally easy to work on. I usually had to go through the boards and find the solder joint or wire that had fatigued and re-solder that joint.

Also keep in mind that all of the servo cards run on magic gray smoke. When you make a mistake and short them out, it lets out the magic smoke and they never work again. After that I tried to find a way to use those giant brushed servos with a more modern controller and found a company that thought they could do it, but is seemed like I needed new encoders and abandon the glass scales. I got it running and sold it instead.