[RCaffin]

Hi all

Both my spindle motors are Baldor 180 V 2.5 A DC brushed motors, and I am not going to replace them. (Very rugged beasts they are.)
But the KBMG-212D (230VAC) spindle driver I was using went mad so I had to shoot it ... it was pulsing 10A surges out ... shorting one or two of the SCRs I would imagine.
Are there any alternatives drivers to the KBMG?

Note: the KBMG-212D is direct off the mains. It does not need a separate power supply.

Cheers
Roger

[hjl4]

RCaffin, just a suggestion here, SCR motor controllers are not the way to go anymore. They are hard on brushes. I just went thru a dead spindle driver and replaced it with a KBRG-255 and what a mistake. Motor heats up way too much and is loud. It used to be quiet and ran cool even after a whole days work.
So my suggestion, is a mosfet or igbt motor control.
If you are using Mach3, check out Advanced motor controls. PWM in and pulsed DC out to regulate speed and power.
Also to determine the proper size of drive you need, you should check the actual output of the KBMG at full speed.
Just because the motor says 180VDC, it doesn't mean that's what it was running at full speed.
AL the man, can make more sense of this. He'll steer you in the right direction if he sees this post.

[RCaffin]

Hi Hnery

SCR motor controllers are not the way to go anymore. They are hard on brushes.

Yes, a shade old, I know.

If you are using Mach3, check out Advanced motor controls.

Yes, I am using Mach3. Do you mean Advanced Motion Controls?
Any particular models you would suggest?

Just because the motor says 180VDC, it doesn't mean that's what it was running at full speed.

True, but in this case I think it was getting close to 180 V. Certainly, over 150 V.

Thanks
Cheers
Roger

[hjl4]

Yes, Advanced Motion Controls. They make servo drive and such. You can get them fairly cheap on Ebay.
A 2.5 amp unit should be fairly cheap. The 180VDC can be a challenge. You'll have to do your homework. Like I said, AL, would be the best guy to go technical with.
There are also some Mosfet/PWM motor drives that are on Ebay claiming 90/180V output. Just make sure they are not SCR. It is a world of difference when you can barely hear the DC motor turning. SCR's always have a hum that is quite loud on large motors.

[RCaffin]

Yes, Advanced Motion Controls. ... The 180VDC can be a challenge.

Challenge is right. So far I can't find anything over 80 V.
Maybe I have the wrong search strings? Suggestions?

Cheers
Roger

[hjl4]

Advanced Motion Control Servo Amplifier BE25A20 Rev H Motor Controller Drive | eBay

This is just an example. I know you don't need the 25 amps peak, but just what's available. When doing your search for these AMC drives, the breakdown of the numbers is simple. In this case, 25A20, 25A=Amps peak, 20=Volts input x 10.
Here is a pdf.



A better alternative would be a KBWT-26 from KB electronics. PWM controlled. Again you have to do your homework here.
KBWT 26 Pulse Width Modulated (PWM) DC Drive

Good luck.

[RCaffin]

Hi Henry

Thanks for the suggestion. I have to say, I find the AMC data totally confusing - the way they present it anyhow. My first impression was that the drive requires both a tacho and Hall effect feedback - neither of which is available from my motors. The block diagram they offer shows Encoder channels A & B shorted together. ODD. The power output stage shows it driving a 3-phase output. My motor is single phase.
I am sure they are great drives, but I suspect their data sheets discourage more would-be customers than they ever dreamed of. Strange ...

I know about the KB series. They are SCR drives, and that is what I have, blown up. I would like, if at all possible, to move to a MOSFET drive. That is actually shade harder, as finding MOSFETs which can handle several hundred volts is far more difficult. 80 V: easy stuff. It seems that high-voltage DC motors are not so popular.

Cheers
Roger

[hjl4]

Hello again.
Ok, forget the AMC drives.

But the the KBWT-26 is a MosFet drive. here is the datasheet. I think it would be perfect for your motors.

If you read the description it mentions the advantage over SCR drives.

[RCaffin]

Hi Henry

KBWT-26
Now why couldn't I find that on their web site???
They ALL seem intent on hiding their products behind a wall of obscurity. Mumble.
I will pursue that one.
Any recommendations for suppliers? Ah - I am in Australia, but USPS functions just fine.

Many thanks
Roger

[hjl4]

I think you would be better off doing a search for a supplier. Compare prices between them.
Sometimes an hour spent looking for a good price can really pay off.

KBWT-26 KB Electronics 230 VAC, 6.0 Amps, 180 to 260 VDC ARM (8615)

now, If only I could find myself a 180 volt dc 50 amp controller similar to this, my search would also be over.

Glad to have helped. Take care.

[RCaffin]

Hi Henry

Can't help with 50 A, but the DG4S-16032 (CNC4PC has them) comes close, with 160 V and 32 A. Would that suffice for a while?

Cheers
Roger

[RCaffin]

From a few months ago, but never mind.
I bought a KBWT-26 unit. It has good bits and not-so-good bits (so far).

Good:
The spindle motor is now VERY quiet in comparison to what it was like with an SCR-based unit. Positively purrs. Maybe the motor will run cooler too.
The unit can actually go well above the 180 V spec. There are two control pots for that: one sets the minimum output voltage (0-30 V, set to 0 V) while the other one sets the maximum output voltage. I can set the maximum output voltage to better than 1 V quite easily. I set it to 182 V.
The unit can be controlled by a floating potentiometer, and is very responsive to it. Vroom vroom.
The unit can have accel and decel time constants set separately, 0.2 sec to 12 sec, so you don't get a huge slam when it is turned on.
The unit has an enable input - actually a disable input which activates when shorted. I use the NC contacts on a miniature PCB relay for this, so it defaults to OFF.

Not-so-good (so far)
The unit is meant to be able to handle PWM input via a supplied opto-coupler circuit. The circuit itself works, but the response to this input is (so far) quite crazy. It takes maybe 10 seconds to respond at all, then drifts upwards steadily. In addition, I have to generate about 2.5 V (average) to get the unit to start responding at all. Weird!

Fairly obviously, I must be doing something WRONG! But I don't know what. Does anyone have any idea?
If all else fails I will implement an optically-coupled potentiometer using H11D1M chips or similar, and put that in place of the simple pot.

Minor problem with Mach3: it seems that the PWM output is muted until either M3 or M4 is issued. Bother! makes debugging harder.

Cheers

[Al_The_Man]

Are you using a opto or isolated PWM input as suggested in the manual?
If you have the resources it may be worth testing it with a simple 555 PWM controller set up.
Did you try issuing a M3 in Mach and then connect after 10 secs to the drive to see if any delay at that point?
Al.

[RCaffin]

Hi Al

Are you using a opto or isolated PWM input as suggested in the manual?

Exactly as suggested in the manual.

If you have the resources it may be worth testing it with a simple 555 PWM controller set up.
Did you try issuing a M3 in Mach and then connect after 10 secs to the drive to see if any delay at that point?

Did essentially the same by switching between the pot circuit and the PWM circuit.

Spent some time measuring things just now.
The V+ on the KBWT-26 is labeled +5 V, but at rest (no drive output) it is +7.1 V. When the drive is activated (OC IL1&IL2) that voltage drops to 6.0 V. When the drive is deactivated the +6 V voltage rises at once back to 7.1 V. The output of the PWM coupler depends on that voltage so the spindle speeds UP briefly before it shuts down. Alarming at first.
What's more, by coming in on P2 with the output of their recommended Opto circuit, the speed does not rise for about 5 seconds, and then just keeps rising slowly, for a long way. One could believe that there is a long time constant and the start of the slew is seriously negative - which would be very strange.
On the other hand, if I use the pot arrangement per their data sheet the speed is very responsive to the pot setting, and quite stable (as measured by the Mach3 Rev DRO).
I wish I had the circuit for at least the input stage of the KBWT-26!

So, it seems that while the pot circuit is stable, the voltage circuit is sort-of open loop and drifts off badly. No idea why. Got any suggestions? I will add that the whole system worked fine for a year or more before the previous SCR-based drive blew up. I am scratching my head.
(I have full electronics workshop with all gear, left over from research career.)

Cheers
Roger

[Larken]

Hi Henry

Thanks for the suggestion. I have to say, I find the AMC data totally confusing - the way they present it anyhow. My first impression was that the drive requires both a tacho and Hall effect feedback - neither of which is available from my motors. The block diagram they offer shows Encoder channels A & B shorted together. ODD. The power output stage shows it driving a 3-phase output. My motor is single phase.
I am sure they are great drives, but I suspect their data sheets discourage more would-be customers than they ever dreamed of. Strange ...

I know about the KB series. They are SCR drives, and that is what I have, blown up. I would like, if at all possible, to move to a MOSFET drive. That is actually shade harder, as finding MOSFETs which can handle several hundred volts is far more difficult. 80 V: easy stuff. It seems that high-voltage DC motors are not so popular.

Cheers
Roger

I think your looking at a newer Brushless 3phase AMC drive that has an encoder input. You need a older basic Brushed AMC drive.

Also i can make my Viper200 run at 180 volts for you to try. You can run off a rectified half bridge 220 volts (that gives a 170Vdc) . A few other people are running them on 180volt spindles. It would be running in Step/Dir mode from Mach3 instead of 0-10 volt mode and you would need an encoder.

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EDIT: Hmm, this thread has me thinking, maybe there is a market for a DC spindle drive... so its fairly easy for me to add a 0-10 volt input to my Viper 200.

PWM200 DC Spindle Drive, ViperServo

( The problem with running a step/dir closed loop spindle drive from Mach3 was if you hit the estop while running full speed, it tries to stop and dumps a lot of power back into the drive, but an openloop PWM drive with a programmable accel and decel saves the drive from sudden high current. )

thanks
Larry K

[Al_The_Man]

I have the circuit for the KBIC, I don't know if the input is similar, the input goes to a common Opamp, the accel circuit is also on the input.
Al.

[RCaffin]

Hi Al

I have the circuit for the KBIC, I don't know if the input is similar, the input goes to a common Opamp, the accel circuit is also on the input..

Indeed? I imagine that's quite possible. Could I get a copy from you to see how it compares, maybe please?

I now suspect that at least one of my assumptions is wrong. I had assumed that the IL1/2 inhibit input was suitable for routine use as an Enable signal. I now think that is wrong, and that it is meant as an emergency eStop input. So the appearance the output gave of being just part of a long time constant might be entirely correct.

I should add here that there are other differences between the voltage control and the pot control. The pot control gives a more or less linear response from 0% to 100% of the setting, while the voltage control does not start to move the motor until there is about 2.5 V on it. Then the speed rockets as the voltage goes up slightly. I suspect an open-loop amplifier in there somewhere! That makes a second assumption which might be wrong.

Comment: I do not think KB are doing themselves any favours with their extremely minimal technical data. Maybe their marketing guys think their doco looks just great, but the customers disagree. Strongly.

So yes, I would love a copy of any circuit diagrams around.

Cheers
Roger

[Al_The_Man]

I will send it over, the I1 & I2 are intended for disable, especially when using a reversing relay or switch.
Their enclosure units that have the pot and special switch that inserts a braking resistor and also engages the L1/L2 and also implements a mechanical stop to prevent switching from fwd to run in one sweep.
The AMC DC and BLDC drives can both be used for DC brushed motors without tach or encoder, it just offers tighter control when used in the velocity loop mode.
But they will run as velocity drives and also have bi-directional control with pot without switching.
Al.