Electrocraft BLDC motor, need some spec's.

[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]

Originally Posted by lucas 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....
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.