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Author Topic: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?  (Read 23298 times)

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Offline Hood

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #10 on: May 03, 2010, 04:28:31 PM »
Some of the MPL motors are rated speed of 8,000 rpm

The problem with the intelligent encoders that are on the MPL motors (or some, as some have normal encoders) is that they communicate with the drives and contain the info about the motor they are fitted to. In other words you would need to use them on the motor they came off I think.
They are Sick Stegmann SRM encoders or at least some are because I think there are also SRS ones on some motors.

Hood

Offline Dan13

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #11 on: May 03, 2010, 04:35:24 PM »
So it makes things even more complicated :(

Any idea about the possible relationship between the motor poles number and encoder commutation? As far as I know you simply put the number of poles in the drive and it makes the calculations of the waves based on it. Have no clue what does it have to do with the encoder itself?

Daniel

Offline Hood

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #12 on: May 03, 2010, 04:43:13 PM »
Are you referring to the intelligent encoders? If you are then I presume that is where the programmaed part of the encoder comes in as it will contain the info about the poles. Never done much reading up on it though so its just an assumption.

One of the MPL motors I bought to get the normal encoder off had a very tidy encoder on it that looked like it would possibly be capable of speed but afraid I cant even remember what make/model it was so cant look up the specs. Normally the AB motors had Renco encoders on them but looked at their site and dont see any max speed info there :(
Hood

Offline Dan13

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #13 on: May 03, 2010, 04:50:46 PM »
I was referring to these:

http://www.quantumdev.com/products/optical_encoders/qd145.html

See that they differentiate the models by the number of poles. Max speed for these is only 8,000RPM though :(

Daniel

Offline Hood

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #14 on: May 03, 2010, 05:00:45 PM »
Not sure I understand your question, these seem to be normal incremental encoders and as such you need the commutation channels on them to match your motors pole pairs. Or are you meaning something else?

Found some info on encoders saying 30,000rpm but not sure if they are any use or not as have not really read it yet. http://www.moog.com/literature/MCG/opticalencoders.pdf

Oh and if this is for a spindle you may not even need commutation signals, well not sure about the Ultra 5000's but the 3000's can do an auto sense for commutation startup which on a spindle I dont think would be an issue.
Hood
Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #15 on: May 03, 2010, 05:56:14 PM »
Basically a resolver produces a sin/cos signal, they require analogue detection circuitry to work, I have some Allen Bradly drives that are resolver only, the encoder signal is extrapolated from this in the drive for output to a controller,  this method has been done for some time now for AC sinusoidal commutation, this is opposed to BLDC commutation which typically uses three commutation tracks on the encoder disk, used to be known as Hall effect due to 3 descrete hall effect devices used.
There are current sinusoidal drives that use an initial marker signal and then produce the commutation from the encoder pulses.
BTW, Since  Allen Bradley bought out Electro-Craft, their motor and drives have principally been Electro-Craft, often the same part number.
If you replace an encoder on a motor to use as AC or BLDC, the pole count and pole position has to be known or detected and the encoder lined up with the pole position.
Someone mentioned Renco, they have now been taken over by Heidenhain and their product line has been trimmed quite a bit.
Nosmo.

Offline Dan13

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #16 on: May 04, 2010, 03:44:37 AM »
Not sure I understand your question, these seem to be normal incremental encoders and as such you need the commutation channels on them to match your motors pole pairs. Or are you meaning something else?

That's what I had thought - you put a commutating encoder on a motor and its 3 hall signals have to match the motor poles. I hadn't realized that the NUMBER of poles had any affect - still same three hall signals from the encoder. But from that link it seems that an encoder is specific to a motor with the NUMBER of poles it was designed for. Am I missing something here? Are the signals from an encoder on a 4 pole motor different from those of an encoder on a 6 pole motor?

Found some info on encoders saying 30,000rpm but not sure if they are any use or not as have not really read it yet. http://www.moog.com/literature/MCG/opticalencoders.pdf

Yes, these look good. They are not commutating though.

Oh and if this is for a spindle you may not even need commutation signals, well not sure about the Ultra 5000's but the 3000's can do an auto sense for commutation startup which on a spindle I dont think would be an issue.
Hood

Ah... Hadn't noticed this detail in the manual before. This is perfect! The motor IS meant for a spindle indeed. Thanks for pointing me to this. So I wonder now what if I fed the Sin/Cos channels from the resolver to the the Ultra5000 while the resolver Ref is being excited by a DC voltage.. ??? Does it make any sense? In second thought, seems it wouldn't work at low speeds because the resolver wouldn't be able to induce the Sin/Cos when the magnetic field changes slowly. But with a high frequency excitation I think the drive "will be confused"... Can you tell me how does the Sin/Cos encoder work? Is it the same phasing like normal, square wave signal, encoder?

Daniel

Offline Dan13

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #17 on: May 04, 2010, 03:50:40 AM »
Thanks for the info Nosmo. Does it make the AB drives BLDC commutation?? They do expect hall signals (the Ultra series).

Daniel

Offline Hood

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #18 on: May 04, 2010, 04:17:04 AM »
Are the signals from an encoder on a 4 pole motor different from those of an encoder on a 6 pole motor?

Never looked deeply into it but I would assume that it is the spacing of the three signals that would let your drive know the commutation startup. So if it was two pole the signals would be 180 out, 3 pole 120 out, 4 pole  90.


Yes, these look good. They are not commutating though.

If using self sensing commutation wont be required.

Ah... Hadn't noticed this detail in the manual before. This is perfect! The motor IS meant for a spindle indeed. Thanks for pointing me to this. So I wonder now what if I fed the Sin/Cos channels from the resolver to the the Ultra5000 while the resolver Ref is being excited by a DC voltage.. ??? Does it make any sense? In second thought, seems it wouldn't work at low speeds because the resolver wouldn't be able to induce the Sin/Cos when the magnetic field changes slowly. But with a high frequency excitation I think the drive "will be confused"... Can you tell me how does the Sin/Cos encoder work? Is it the same phasing like normal, square wave signal, encoder?

Daniel



Still dont think the resolver will work or I would imagine AB would mention it, then again only  one way to find out ;)

Thanks for the info Nosmo. Does it make the AB drives BLDC commutation?? They do expect hall signals (the Ultra series).

Daniel
As far as I am aware BLDC and AC servo motors are one in the same but it is the drives that are different in the way they do the commutation. The Ultra drives are AC.

Hood

Offline Dan13

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #19 on: May 04, 2010, 07:01:54 AM »
Never looked deeply into it but I would assume that it is the spacing of the three signals that would let your drive know the commutation startup. So if it was two pole the signals would be 180 out, 3 pole 120 out, 4 pole  90.

I am afraid this is not correct as there are always 3 signals and they are equally spread along the 360 degrees of one revolution, meaning there would always be a 120 degrees phase shift between them. Also, brushless motors are essentially 3-phase motors so the control signal is always 3 phase 120 degrees apart and the commutation signal must match. You can also see this in the Ultra manuals where they specify the signals' phasing - nothing mentioned about the motor poles number. As I see it, the number of poles only dictates the control signal frequency to achieve a given speed and the commutation essentially follows that frequency.

Still dont think the resolver will work or I would imagine AB would mention it, then again only  one way to find out ;)
Yep... will do some reading on Sin/Cos encoders and try to understand their operation. Hopefully the Sin/Cos signal of these encoders and those of a resolver are the same and AB say their Ultra drives don't support resolvers merely because their drives don't have an AC excitation signal required for resolvers. In this case an external signal might be used I assume.

As far as I am aware BLDC and AC servo motors are one in the same but it is the drives that are different in the way they do the commutation. The Ultra drives are AC.

Hood

Yes, I also thought the Ultra drives were AC, but if I understand what Nosmo says, then since they are using hall feedback they are BLDC??  :-\

Daniel