2 Phase Servo Control

[PointB]

Does anyone know a good source of info on 2-phase 6 pole perm magnet servo control? I'm using resolver feedback.

All web and book info I can find is 3 phase, which I can't use in my application.

 

[sreid]

Is the motor really a two phase motor? This is very rare.

 

[ScottI2R]

Hi,
Why is your app 2 ph. critical?

Thanks,
Scott

In a hundred years, it isn't going to matter anyway.

 

[PointB]

Why? It is very powerful for its size, and it can withstand extreme environments. 3-phase may be possible in the future, but for now I'm stuck. Yes, this motor is rare - it is custom engineered, and very expensive.

Trouble is, I don't have much DC motor experience, and I'm having trouble just getting started.

Any ideas?

 

[blacksea]

Your 2-phase motor is stepper one. And of course maybe controlled by any stepper motor controller with feedback. Lok at Allegro ICs for example.

 

[nbucska]

What is the voltage and current? what is the speed range?
Do you need position or only speed control? accuracy?


Plesae read FAQ240-1032
My WEB: <

http://geocities.com/nbucska/>

 

[sreid]

Please supply motor details. Historically,two phase servo motors had a sin/cos phase relationship.

 

[nbucska]

blacksee:
Stepper motors have hundreds of poles not 6.


Plesae read FAQ240-1032
My WEB: <

http://geocities.com/nbucska/>

 

[PointB]

Two phase Permanent Magnet Brushless DC (PM BLDC). The motor has six poles and uses resolver commutation. The resolver requires an excitation voltage of 4.0 Vrms at 20 kHz, transformation ratio is 0.5

The current is about 2 amps, 28 VDC. The motor will be operating at about 10,000 rpm

I am more concerned about position control. I am slightly concerned about rotor inertia and backlash, but I don't anticipate a problem

I'm told 2-phase is 5-10% more efficient.

 

[coconutalley]

Just curious, how many wires does it have (don't count resolver wires)? If you have 2 then it is likely a
brushed dc motor (I've been wrong). If you have 3 or 4 then it is likely a 2 phase motor.
The resolver is just a feedback device (gives sinusoidal analog signals) and you'd need a resolver converter IC which will give you signals that you can process digitally. Do a resolver converter in Google and you'd come across the IC and app notes. The number of poles gives the motor more torque. Basically, it is just more coils in series but maybe interwoven with the other phase. Poles are paired to give it N and S magnetic polarity.
You'd need to come up with an algorithm to commutate every 0 to 180 degrees electrical. You'd need to align the resolver with the 0 position of the rotor if it has not been done or you can offset in firmware. Good luck.
CA

 

[PointB]

This is certainly a 2 phase brushless motor.

Thanks for the feedback. How about the power requirements? Is there an easy (cheap) way to generate the sinusoidal excitation?

 

[cswilson]

The few 2-phase brushless servo motors I have seen have 2 electrically independent phases, like most stepper motors. So your power stage must be 2 independent H-bridges (like most stepper drives). However, unlike stepper drives, you want to run this closed loop with resolver feedback.

I doubt that you are going to find an integrated solution. Systems with resolver feedback are usually for 3-phase motors so the power-stage topology is different, and the algorithm may not be flexible enough to support phases with 90-degree instead of 120-degree spacing.

It looks like we could provide you with all the pieces you need to do this, but it would be an expensive solution and probably overkill for what you need. You can contact me offline if interested.

Curt Wilson
Delta Tau Data Systems

 

[itsmoked]

You have not mentioned the point of your endeavor so I will assume you are developing something for controlling the BLDC and suggest you look at this tool. It is excellent in my experience with it.

If you just need to make one work... Go for Curt's suggestion.

http://www.microchip.com/stellent/i...E&nodeId=1406&dDocName=en024213&part=DM183021

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[coconutalley]

The cheap way is to buy a drive for 2 phase motor. You still have not indicated the number of wires it has. Need to determine if it is open phase or tied. Also, is the back emf trapezoidal shape?

 

[waross]

Is there any way to send a three phase output from a three phase driver into a pair of Scott connected transformers to derive two phase? Can you keep the drive frequency high enough to avoid saturating the transformers?
respectfully