Tauno Voipio wrote:

> The only way to safely control the rotation speed
> of an induction motor is to control the frequency
> and feed voltage synchronized to each other.
> 
> If you simply drop the input energy by clipping a
> part of the feed AC off, the motor quickly stalls
> when you're getting more than a couple of then of
> percent off the nominal speed.
> 
> Maybe the best way to control an induction motor
> is a DSP method, called rotor vector synthesis.

The book (whose details I have already posted) calls it "Full Vector
Control" but is as you describe, controlling the applied voltage and the
frequency of operation.

The following papers look interesting:-

<http://www.eu.necel.com/_pdf/U16483EE1V0AN00.PDF>
<http://www.iee.or.jp/trans/pdf/2000/0010D_1165.pdf>
<http://www.elkraft.ntnu.no/norpie/10956873/Final Papers/030 - Salomaki.pdf>

-- 
********************************************************************
Paul E. Bennett...............<email://Paul_E.Bennett@topmail.co.uk>
Forth based HIDECS Consultancy
Mob: +44 (0)7811-639972
Tel: +44 (0)1235-811095
Going Forth Safely ..... EBA. www.electric-boat-association.org.uk..
********************************************************************

On Nov 5, 6:49?pm, richard.melik...@gmail.com wrote:
> Hello,
>
> I'm looking for a good book on the topic of motor control with
> microcontrollers, with emphasis on PWM algorithms. I'm interested more
> in the PWM side of things than in control theory (PID), as the motor I
> need to control is an AC motor that only has to be speed-controlled
> (it's a big ventilation fan). From searching the net it appears that
> this is a topic with a lot of ad-hoc solutions, so I would really love
> to hear recommendations of books and/or good online resources for
> learning the topic.
>
> Thanks in advance,
> R

Dont waste your time, modern inverters use a vector control algorithm,
but if you must IR "power train" development kits are available as
well as a Fujitsu starter kit for inverters.

Jim Stewart wrote:
> HardySpicer wrote:
> 
>> On Nov 6, 7:49 am, richard.melik...@gmail.com wrote:
>>
>>> Hello,
>>>
>>> I'm looking for a good book on the topic of motor control with
>>> microcontrollers, with emphasis on PWM algorithms. I'm interested more
>>> in the PWM side of things than in control theory (PID), as the motor I
>>> need to control is an AC motor that only has to be speed-controlled
>>> (it's a big ventilation fan). From searching the net it appears that
>>> this is a topic with a lot of ad-hoc solutions, so I would really love
>>> to hear recommendations of books and/or good online resources for
>>> learning the topic.
>>>
>>> Thanks in advance,
>>> R
>>
>>
>> PWM is for dc motor control. The average level gets applied to the
>> motor. If you want to control the speed of an ac motor then you can
>> use other methods.You could synthesis your own variable frequency AC
>> but that's not PWM.
> 
> 
> Someone can correct me if I'm wrong.
> 
> As the speed of an AC motor approaches
> zero, you must somehow reduce the amplitude
> of the waveform to limit current draw. This
> likely would involve PWM modulation to
> generate a reduced amplitude sine wave.

The relation of motor voltage and rotation
speed applies to all electric motors, but
certain motors do not follow the input voltage
alone.

If you have a shaded-pole induction AC motor, the
motor creates the torque for running from the lag
between the feed AC frequency and the rotation
speed of the rotor.

When the lag grows, the motor quickly loses the
torque and becomes essentially a shorted transformer.

The only way to safely control the rotation speed
of an induction motor is to control the frequency
and feed voltage synchronized to each other.

If you simply drop the input energy by clipping a
part of the feed AC off, the motor quickly stalls
when you're getting more than a couple of then of
percent off the nominal speed.

Maybe the best way to control an induction motor
is a DSP method, called rotor vector synthesis.

-- 

Tauno Voipio
tauno voipio (at) iki fi

HardySpicer wrote:
> On Nov 6, 7:49 am, richard.melik...@gmail.com wrote:
>> Hello,
>>
>> I'm looking for a good book on the topic of motor control with
>> microcontrollers, with emphasis on PWM algorithms. I'm interested more
>> in the PWM side of things than in control theory (PID), as the motor I
>> need to control is an AC motor that only has to be speed-controlled
>> (it's a big ventilation fan). From searching the net it appears that
>> this is a topic with a lot of ad-hoc solutions, so I would really love
>> to hear recommendations of books and/or good online resources for
>> learning the topic.
>>
>> Thanks in advance,
>> R
> 
> PWM is for dc motor control. The average level gets applied to the
> motor. If you want to control the speed of an ac motor then you can
> use other methods.You could synthesis your own variable frequency AC
> but that's not PWM.

Someone can correct me if I'm wrong.

As the speed of an AC motor approaches
zero, you must somehow reduce the amplitude
of the waveform to limit current draw. This
likely would involve PWM modulation to
generate a reduced amplitude sine wave.

On Nov 6, 7:49 am, richard.melik...@gmail.com wrote:
> Hello,
>
> I'm looking for a good book on the topic of motor control with
> microcontrollers, with emphasis on PWM algorithms. I'm interested more
> in the PWM side of things than in control theory (PID), as the motor I
> need to control is an AC motor that only has to be speed-controlled
> (it's a big ventilation fan). From searching the net it appears that
> this is a topic with a lot of ad-hoc solutions, so I would really love
> to hear recommendations of books and/or good online resources for
> learning the topic.
>
> Thanks in advance,
> R

PWM is for dc motor control. The average level gets applied to the
motor. If you want to control the speed of an ac motor then you can
use other methods.You could synthesis your own variable frequency AC
but that's not PWM.


Hardy

On Nov 5, 7:49 pm, richard.melik...@gmail.com wrote:
> Hello,
>
> I'm looking for a good book on the topic of motor control with
> microcontrollers, with emphasis on PWM algorithms. I'm interested more
> in the PWM side of things than in control theory (PID), as the motor I
> need to control is an AC motor that only has to be speed-controlled
> (it's a big ventilation fan). From searching the net it appears that
> this is a topic with a lot of ad-hoc solutions, so I would really love
> to hear recommendations of books and/or good online resources for
> learning the topic.
>
> Thanks in advance,
> R

For the PWM side of things check for SPRA524 application note on TI's
site

Regarda

Mitja

Jerry Avins wrote:
> Tim Wescott wrote:
>> DJ wrote:
>>>
>>>> I'm looking for a good book on the topic of motor control with
>>>> microcontrollers, with emphasis on PWM algorithms. I'm interested more
>>>> in the PWM side of things than in control theory (PID), as the motor I
>>>> need to control is an AC motor that only has to be speed-controlled
>>>> (it's a big ventilation fan).
>>>
>>> I don't think there is such thing as PWM algorithm - there might be 
>>> PID algortithm with PWM output I guess.
>>> Anyway I belive you will not get away from PID in this case 
>>> especially if it's big fan with long response time and inertion. You 
>>> just won't be able to run it at constant speed either using PWM or by 
>>> other means. Anyway coding PID is not a rocket science should give it 
>>> a try.
>>
>> Whether you need a PID controller depends on what you're trying to do. 
>> An induction machine will give you about 500 RPM of slip; if you only 
>> need to be that close then you don't need the PID controller.
> 
> %oo 5pm at what frequency? How many poles?
> 
I was thinking someone was going to ding me on pole count when I wrote that.

"About" 500RPM.  So, anything from 0 to 750, or more.  That should cover 
any number of poles.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Jerry Avins wrote:

   ...

> %oo 5pm at what frequency? How many poles?
   ^Capital '5'. :-)

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

DJ wrote:
> 
>> I'm looking for a good book on the topic of motor control with
>> microcontrollers, with emphasis on PWM algorithms. I'm interested more
>> in the PWM side of things than in control theory (PID), as the motor I
>> need to control is an AC motor that only has to be speed-controlled
>> (it's a big ventilation fan).
> 
> I don't think there is such thing as PWM algorithm - there might be PID 
> algortithm with PWM output I guess.
> Anyway I belive you will not get away from PID in this case especially 
> if it's big fan with long response time and inertion. You just won't be 
> able to run it at constant speed either using PWM or by other means. 
> Anyway coding PID is not a rocket science should give it a try.

Whether you need a PID controller depends on what you're trying to do. 
An induction machine will give you about 500 RPM of slip; if you only 
need to be that close then you don't need the PID controller.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Tim Wescott wrote:
> DJ wrote:
>>
>>> I'm looking for a good book on the topic of motor control with
>>> microcontrollers, with emphasis on PWM algorithms. I'm interested more
>>> in the PWM side of things than in control theory (PID), as the motor I
>>> need to control is an AC motor that only has to be speed-controlled
>>> (it's a big ventilation fan).
>>
>> I don't think there is such thing as PWM algorithm - there might be 
>> PID algortithm with PWM output I guess.
>> Anyway I belive you will not get away from PID in this case especially 
>> if it's big fan with long response time and inertion. You just won't 
>> be able to run it at constant speed either using PWM or by other 
>> means. Anyway coding PID is not a rocket science should give it a try.
> 
> Whether you need a PID controller depends on what you're trying to do. 
> An induction machine will give you about 500 RPM of slip; if you only 
> need to be that close then you don't need the PID controller.

%oo 5pm at what frequency? How many poles?

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������