[lucas]

I have bought 4 of these (Nema 34) on Ebay for a good price but without info.
Later on I also aquired the drives wich were used to drive these on a prototype machine, they are a special version of the B12A6F drive from Advanced Motion Controls (60VDC, 6A max), but I'm not sure if they are a perfect match for the motor.

Is there anyone who can provide some more info on these motors?
Are the drivers optimal or is there potentially more power?

I am considering using one as a spindle motor (low speed ER16) but am afraid they won't have enough torque.

Thanks in advance,
Luc.

[unterhaus]

I have bought 4 of these (Nema 34) on Ebay for a good price but without info.
Luc.

For a spindle motor, you may want to gear down at least a little. There is an AB equivalent to that motor. I don't know what happened to the electrocraft page on the AB site, I guess it got sold with emerson to blador.

[lucas]

Thanks for the reply, would you have any idea of the approx. output power of this one compared to the watt's of a AC induction or brushed DC motor?

The benchtop mill for wich I need a spindle motor is almost finished and I have 3 options to choose from, the weight of the motor is a limiting factor.
The spindle is a simple DIY made from a ER16 extension shank and it's main purpose would be to mill aluminium and drilling.
The drilling will need slow speed but high torque, a belt reduction will be needed but I also would like to regulate the spindle speed and still obtain a decent torque at low speed.

This is the stuff I have and need some help to choose the best solution:
1: AC induction motor with VFD, a 500W motor would be the absolute max. for weight and space.
2: Brushed 48V DC motor with tach ,don't have specs either, but it's approx 50% bigger than the BLDC (Diam. 80mm, lenght 170mm).
3: The Electrocraft BLDC one.

A brushless motor is the best solution from what I have learned by reading "the zone" but I haven't read everything and could be wrong..

Thanks in advance,
Luc.

[unterhaus]

http://literature.rockwellautomation...n519_-en-p.pdf
Pretty sure this matches your motor
Don't see any performance specs for whatever reason. It's really annoying that they have removed the electrocraft docs.

[Al_The_Man]

I have most of the Reliance and ElectroCraft specs in hard copy, They do appear to be N series Nema 34, if you give me the motor dimensions, I can match the specs up to this.
Al.

[lucas]

Thanks guys,

you are both pointing at the N-series, I have the info on these from Allen Bradley and the dimensions match the N-3406 exactly except for the L: it states 5.67 inch and I measure 5.65...
The winding resistance matches also but the inductance is slightly off: specs say 6.1mH measurement says 5.79mH.
When I spin the motor at approx. 500RPM and measure with a scope on one winding there is a nice sine wave 15Vpp and a period of 80msec (= 125HZ and this matches the approx. 500RPM).
My motors also have the same feedback: 3 tachsignals, differential encoder and a thermostat.

But now the stuff wich I don't understand:
1: As far as I know these N-series are AC servos, can they be driven by a BLDC drive, this was done on the machine they come off?
Quote from the drive manual: "The B15A Series PWM servo amplifiers are designed to drive brushless DC motors".
I know that AC and DC brushless motors are very similar but don't know the exact differences. DC's are driven by a trapezium drive and AC's by a true 3 phase AC, this is all I know about this.

2: The motor datasheet says KE Voltage Constant V/krpm: 21 and max speed 6000RPM, this would mean something like 100V to run the motor at 5000RPM?
The machine used 48V and thus a max. speed of 2000RPM?

3: I still don't have a clue on the continuous output power so that I can compare with a regular ac motor with VFD or a brushed DC one.

Could it be that Electrocraft made DC brushless motor's or is this really a N-3406?
If it is then I could probably use a DDM009 AC drive Ultra 100 from Allen Bradley wich I happen to have (max. continuous power output 1.2KW...).

Thanks very much for your help,
Luc.

[Al_The_Man]

The spec gives both sine wave torque and square wave torque, if you use in in the BLDC mode, you should be able to use the square wave torque, they a fairly close anyway.
Sine=0.169Nm/A Square = .191Nm/A
I make the max voltage as 285v for 6000 rpm and 238v for 5000.
(20v/kRPM peak value phase to phase sinusoidal).
I hope you have the matching connectors and leads as these cost a fortune from AB.
If the amp you have is AC sinusoidal, you will need to check if the encoder alone is compatible for sinusoidal commutation.
Otherwise there are 3rd party drives like Advanced Motion that should operate them.
Al.

[lucas]

Thanks Al,

Does this mean that you are sure it's a N-3406?

I just finished a decent 48V power supply and will use the B12A6F drive to check the motors.

If it is a N-3406 then the max speed in this configuration should be very low.

And no I don't have the cables for the AC drive, they use very rare connectors, can't find them anywhere, I have seen the prices: much more than what I paid for the drive...

The main issue I still have for this application is the output power of the motor, how would a N-3406 compare to a regular AC or brushed DC motor in Watt's.
I don't understand why these figures aren't stated, they do it for the drives. I'm probably missing a few things or do dumb to understand.........

[Al_The_Man]

You are better off using torque figures where servo's are concerned, manuf seldom quote in HP.
HP is not usually measured but has to be calculated due to dependence on RPM.
HP = (ft-lbs x rpm)/5252
These are not very high power servo's, but it depends on the size of your machine and what rpm you expect/require at the spindle.
I am using a 26In-oz on a 9" x 30" Lathe.
Al.

[lucas]

I didn't have much time to work on this this week but the spindle is finished and looks good.
Yesterday I had another look at the datasheet and boy do I feel stupid.... :withstupi
I was always looking at the table with winding data and trying to figure out the power but couldn't and yesterday I noticed on the last page that the 06 in the model number indicates the continuous torque in LB-IN.
A quick calculation results in 0.476 HP or 350W at 5000RPM, just hope I did it correctly...

This is about the power I want when I compare to similar machines at work and should work fine with some gearing down.

The Advanced Motion B12A6F drive is almost wired up and I hope to have some results maybe tonight, hopefully no smoke.

[lucas]

I spend several evenings trying to get these motors working on the Advanced Motion B12A6F drives but it doesn't work.
I tried 3 motors and 2 drives using the hall signals for commutation but they won't run, the coils are energised and the motor is locked in place, there is no commutation, problem is that I don''t see any signals on the 3 hall outputs.
When I connect only the hall signals to a simple 5V supply and turn the motor by hand: there's no change on the hall outputs..........
The encoder works when connected to the same 5V supply and turned by hand I see the quadrature signals on the scope.
Can't believe all motors have defective hall circuits but it looks like this.
The drives are OK, a MAE brushless motor runs fine.

I could still use them on a AC drive wich uses the encoder for commutation iso the hall's but this would mean that I have to buy new drives whilst I have 3 working ones, not good.

Would it be feasable to attempt a repair? I removed the cap from the encoder/hall assy on one of the drives: 3 tiny SMD IC's and some other SMD components.... I have 30+ years of experience in repairing electronics but not very much on this tiny component level, maybe it are only the sensors inside the motor and that could be doable.
Anyone with experience on this?

Before I do attempt a repair or buy new drives: I need to be sure that my power calculation in the previous post is correct, can someone confirm this?

Thanks,
Luc.

[Al_The_Man]

Some of the Electro_Craft motors are fitted with open collector transistor output for the halls, try taking a 1k resistor to 5v from the Hall outputs.
Al.

[unterhaus]

I don't think they need to be repaired, they are probably worth quite a lot on Ebay, just put AB in the title along with Electrocraft. I haven't seen any deals on the drives that go with those recently, before the new year there were quite a few.
Eric

[lucas]

Al,

I checked the inputs on the AMC drives, they have a pull-up resistor and when I tested the halls on a seperate 5V supply I also tried with a pup resistor but still nothing.

Al: could you please confirm that my power calculations are correct?

@ unterhaus:I bought the 4 motors for approx. 30US$ each wich I think is a super deal, I really would like to use them, one as a spindle motor and the 3 others for real servo positioning on a machine to be build in the year xxxx, like someone elses signature: "too many projects but not enough time".
I could probably sell them on Ebay for much more than what I paid but I don't want to get somebody else in the same troubles as I have now.

As I have nothing to loose: I started carefully to dismantle the encoder/hall assy on one of the motors and have noticed something strange: The hall signals are NOT derived from real hall sensors inside the motor but are optical from the same disc as the encoder and when checking for bad components and measuring the wires to components I found another strange thing: it looks like the 5V supply for the encoder and hall's is mixed between the two, according to the datasheet they should be fully seperate.
Need some more time to get the details on this but it could just be that the motors are not defective and the datasheet is a bit wrong...

Probably (hopefully) more and better news tomorrow...

Thanks to both for your reply and regards,
Luc.

.

[Al_The_Man]

Discrete hall sensors are rarely used these days, the term still carries over to the more common encoder disk optical type, I thought of mentioning that about the power, as Renco are sometimes used on these motors, and they tend to use two supplies for encoder and commutation.
I will post what I have on the power.
Al.

[unterhaus]

I doubt there is anything wrong with the motors. The drives you have really are sub-optimal at best for those motors. If nothing else because they can only run the motors at 1/4 top speed.

If you shop around, you can get a drive like this one:
http://cgi.ebay.com/ALLEN-BRADLEY-13...QQcmdZViewItem
for a reasonable price. I don't know if the DDM-005's will work. There is also a DDM-019 and DDM-030, all of which will work with your motor.
there is also the bru series.

[Al_The_Man]

Yes, I think you are restricting things a little if you intend using these at low rpm spindle, you probabally are going to need some gearing, as high as 10:1 maybe, depending on your actual requirements, operating the drives at low voltage means the motors can never reach their full rpm.
I would think you are going to need a 2 speed set up at least, with these motors.
Al.

[lucas]

I doubt there is anything wrong with the motors. The drives you have really are sub-optimal at best for those motors. If nothing else because they can only run the motors at 1/4 top speed.

If you shop around, you can get a drive like this one:
http://cgi.ebay.com/ALLEN-BRADLEY-13...QQcmdZViewItem
for a reasonable price. I don't know if the DDM-005's will work. There is also a DDM-019 and DDM-030, all of which will work with your motor.
there is also the bru series.

The motors and drives come from the same prototype-machine and the reason I started this thread were my doubts that they are not a perfect match.

I do have exactly the same drive as this one, a DDM-009 but without the very special and expensive cables like Al said before. I bought this one especially to drive these motor's but we still assume that they are real N-series 3406 and I need to be 100% certain that they are and not a special or custom made version, when I am then further "investments " can be made to use this drive.
If I can get the motor running on the "poor sub-optimal" drive then measurements and an evaluation can be made to check if they are N-3406, at the same time I can test all 4 for proper functionality.

@ Al: Didn't know that hall's could be optical, it looks more expensive than the discrete ones but when combined with an encoder on the same disk then it makes sense.
The gearing down will be required, I need to run the motor close to top speed to obtain max. torque at the spindle, T5 belts and a bunch of pulley's are waiting in a box, the reduction can be calculated when I have all rock solid info.

Again thanks to both for the replies, I really need some expert advice on this.

Luc.


Update:
While typing this I combined my hall/encoder measurements with Al's info on Renco and got an idea.
A quick change in connections: I supplied +5V power to both the hall and encoder circuits on the test setup and the motor is spinning !!!!!!:banana::banana::banana:
So there isn't anything wrong with them but with the datasheet, the 5V for the hall's only power's the optical receiver chip but not the hall led, it seems both leds are powered from the encoder +5V and thus power to the encoder is needed even if you don't use it and only want the hall's for commutation.
This "little detail" did cost me a week of evenings and a dismantled motor, hope I can put it together and working again.:devious:

[lucas]

The speed wich I measured today on the AMC drive with a 48VDC supply is approximate 2000 RPM at no load.
This proves that drive and motor are not a good match.

But now I'm confused about the figures wich AL mentioned in a previous post:

Quote:

"I make the max voltage as 285v for 6000 rpm and 238v for 5000"

Al, are these values the supply to the drive or the voltages over the windings?

Quote from the motor's datasheet:
"KE Voltage Constant (4) V/krpm 21
(4) Peak value of sinusoidal phase to phase Volts"

From the speed measurement above a 150VDC drive should run them at 6000rpm, AMC has several drives up to 190VDC, I suspect these should do it and still have some headroom.
Or am I missing something? (I'm a complete newbie on brushless servo's)

Thanks,
Luc.

PS: The dismantled motor is reassembled and works but is a tiny bit noisier than the others, probably because the hall encoder needs adjustment. I'll leave it like this untill I need it and can find an adjustment procedure.

[Al_The_Man]

I think I gave you a bum steer on the previous numbers, I am not sure how I got them.!?
It looks like your original estimate of V/rpm is more like it.
21v/krpm is 126v for 6000rpm, this should be peak to peak at the motor, the supply can be higher, as the drive will limit max current.
You may have to line the commutation up if you moved the encoder disk. I have posted how to do this previously using a 'scope.
Al.