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F3A Results - SPOILER

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Old 08-13-2012, 01:28 PM
  #251
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Default RE: F3A Results - SPOILER

Nice article Dave...[8D]

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Old 08-15-2012, 10:28 AM
  #252
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Default RE: F3A Results - SPOILER

CPLR Interview @ EU Championships (from EU Championships Thread):

http://www.youtube.com/watch?v=1N0Wb...1&feature=plcp

Interesting to hear about his process.He discusses issues relevant to themes in this thread:

Practice time
Aircraft Design
Powerplant choice
Airspeed

He states that he is 33 yrs old and has been flying RC for 32 yrs. Sounds kind of young to start flying...something lost in translation?

Bill
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Old 08-16-2012, 05:40 AM
  #253
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Default RE: F3A Results - SPOILER

' They are brushless DC, our motors are not AC induction motors, which would be more typical of industrial large motors.

http://en.wikipedia.org/wiki/Brushle...electric_motor

All the motors we use operate on that principle, and are all essentially the same with the exception of # turns, winding wire, #poles (which dictates #magnets) and physical size.

Someone can correct me if I got it incorrect.


_____________________________

Chad Northeast '


Quote:
ORIGINAL: apereira

You are correct in my opinion Chad,

The confusion comes from the fact that our brushless motors run on DC with AC type of winding, but they are DC for sure.

Regards

Hi,
Missed this.
The guy who asked is correct ; The motors we use are AC with permanent magnets .
The wiki link Chad posted explains it very well.
Our ESC's are mini inverters/electronic controllers.

Brian
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Old 08-16-2012, 12:11 PM
  #254
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Default RE: F3A Results - SPOILER

Nope, ESC are three phase inverters but without the negative portion of the AC wave so it act like a half wave rectifier and still regulates the frequency as the motor works on magnetic rotating field theory, and that is why old ESC which were low frequency could not reach the power todays highfrequency ESC's, they are DC so the ESC can regulate the power with voltage variation.

If some one knows an ESC applied explanation please post it, as I might be mistaken because in the begining I thought they were all AC, then researched and found what I wrote.

But It may be what you think it is Brian, no problem for me, anyway you just correct everyone, even world champions
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Old 08-16-2012, 01:59 PM
  #255
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Default RE: F3A Results - SPOILER


Quote:
ORIGINAL: apereira

Nope, ESC are three phase inverters but without the negative portion of the AC wave so it act like a half wave rectifier and still regulates the frequency as the motor works on magnetic rotating field theory, and that is why old ESC which were low frequency could not reach the power todays highfrequency ESC's, they are DC so the ESC can regulate the power with voltage variation.

If some one knows an ESC applied explanation please post it, as I might be mistaken because in the begining I thought they were all AC, then researched and found what I wrote.

But It may be what you think it is Brian, no problem for me, anyway you just correct everyone, even world champions
Well, Jeti calls them an AC speed controller. A better description might be phased switching controller... :-)

Regards,
Jason.
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Old 08-16-2012, 03:33 PM
  #256
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Default RE: F3A Results - SPOILER

Might Jeti be calling them an Aircraft (AC) speed controller?
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Old 08-16-2012, 03:48 PM
  #257
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Quote:
ORIGINAL: Doug Cronkhite

Might Jeti be calling them an Aircraft (AC) speed controller?
I don't think so. The line below it says DC speed controller. I believe these are for the old brushed DC motors. They are still a switched controller though.

I found this website which has a good description of how both types work. There is also a bit on the speed controllers and how they work.
http://www.hooked-on-rc-airplanes.co...rc-motors.html

In the end, AC is a little misleading IMHO. It should be switching controller...

Regards,
Jason.
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Old 08-16-2012, 04:02 PM
  #258
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Default RE: F3A Results - SPOILER

Quote:
ORIGINAL: apereira

Nope, ESC are three phase inverters but without the negative portion of the AC wave so it act like a half wave rectifier and still regulates the frequency as the motor works on magnetic rotating field theory, and that is why old ESC which were low frequency could not reach the power todays highfrequency ESC's, they are DC so the ESC can regulate the power with voltage variation.

If some one knows an ESC applied explanation please post it, as I might be mistaken because in the begining I thought they were all AC, then researched and found what I wrote.

But It may be what you think it is Brian, no problem for me, anyway you just correct everyone, even world champions
Hi,
I must admit to not being very expert re this stuff.
Perhaps PC is the best lay mans description - P as in pulse.
When 'they' refer to switching frequency - what is switching ?
I do try to contribute constructively.
I try to avoid being judgmental, unlike yourself, but occasionally it happens in spite of my best efforts.

Brian
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Old 08-16-2012, 04:07 PM
  #259
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Default RE: F3A Results - SPOILER


Quote:
ORIGINAL: serious power


Quote:
ORIGINAL: apereira

Nope, ESC are three phase inverters but without the negative portion of the AC wave so it act like a half wave rectifier and still regulates the frequency as the motor works on magnetic rotating field theory, and that is why old ESC which were low frequency could not reach the power todays highfrequency ESC's, they are DC so the ESC can regulate the power with voltage variation.

If some one knows an ESC applied explanation please post it, as I might be mistaken because in the begining I thought they were all AC, then researched and found what I wrote.

But It may be what you think it is Brian, no problem for me, anyway you just correct everyone, even world champions
Hi,
I must admit to not being very expert re this stuff.
Perhaps PC is the best lay mans description - P as in pulse.
When 'they' refer to switching frequency - what is switching ?
I do try to contribute constructively.
I try to avoid being judgmental, unlike yourself, but occasionally I happens in spite of my best efforts.

Brian
Just use Google....

PWM (Pulse Width Modulation / High rate control)
The control of motor speed is obtained by switching the power to the motor on and off in various ratios e.g. maximum throttle is permanently on, half throttle is on half time, off half time etc. This switching on and off is done many times a second. The speed at which the switching takes place has a large effect on overall efficiency. Early speed controls used what is known as "frame rate" switching, which means that they switched approximately 50 times a second, the same rate as frames of information are delivered over the radio. Most modern ESCs switch at a much higher rate which makes them much more efficient i.e. they lose less power as heat in the controller. Switching rates around 3000 Hz (times a second) are about optimum. Anywhere between 1000 Hz and 5000Hz is acceptable.

Timing Mode
Timing mode is similar to PWM and controls how the on/off switching in the motor. There are two type:
- Soft timing; for 2,4,6 pole motors (Mini AC, Kontronik, Hacker)
- Hard timing; 6 or more pole motors (Jeti Phasor, Mega, Plettenberg).
Hard timing increases both the motor revolutions and the current (up to 20%) with the same propeller and battery pack when compared to soft timing. Hard timing is more suitable for fast flying models.
Always use soft timing initially and after a few flights if the temperature of the batteries, speed controller and motor are below 50 degrees Celsius then it is possible to test the system using the hard timing mode.
Note: Hard timing should not be used with any 2-pole motors (Mini AC, Kontronik, Hacker).

http://www.rcmdirect.co.uk/shop/inde...roducts_id=585

Regards,
Jason.
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Old 08-16-2012, 04:31 PM
  #260
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Default RE: F3A Results - SPOILER

It could be sucessfuly argued that a traditional brushed DC motor when analysed from the commutator onwards is actually a polyphase AC synchronous motor, but I'm really happy just to call what we use a Brushless DC motor with the ESC playing the part of the commutator.

Arguing over any other description is akin to arguing over exactly what type of FET's are in our ESC. I'm happy to just refer to them as FET's.
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Old 08-16-2012, 05:31 PM
  #261
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Default RE: F3A Results - SPOILER

I think I am mistaken or probably there might be different types of ESC control, I remember doing a check a while ago and the voltage was DC.

Well after giving some thought again, I made a check and in fact it is AC, as I measured AC Voltage and frequency on one of my small Hacker setups, so the ESC has the inverters to generate AC current and synchronized as they have to be 120deg apart, the thing is some text call for only a two phase while the other works as a Hall Sensor to syncronize the motor with the ESC, but I read before the motor uses the three phases, but shuts one down in a syncronized manner to use the Hall Sensor for positioning, that is why the sensored motors are supposed to be more efficient, as there are specific hall sensor for positionining leaving the winding fully usable at all times, in any cas I did measure voltage on all three wires, about 4V max on each one on a 3S setup.

I wish a manufacturer of ESC's will actually give some explanation of it, but looks like the inverters in the ESC change the frequency along with the voltage to control the motor speed and using a winding to determine the position of the rotor so it can synchronize the rotating magnetic field and in this way the timing can be set by changing the advance of the rotating magnetic field in relation to the rotor. This is the way I knew it worked, but again, somewhere I read about being DC the way I said before, but right know stand with this latest statement as I just performed the check in house.

Regards
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Old 08-16-2012, 05:35 PM
  #262
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Default RE: F3A Results - SPOILER


Quote:
ORIGINAL: apereira

I think I am mistaken or probably there might be different types of ESC control, I remember doing a check a while ago and the voltage was DC.

Well after giving some thought again, I made a check and in fact it is AC, as I measured AC Voltage and frequency on one of my small Hacker setups, so the ESC has the inverters to generate AC current and synchronized as they have to be 120deg apart, the thing is some text call for only a two phase while the other works as a Hall Sensor to syncronize the motor with the ESC, but I read before the motor uses the three phases, but shuts one down in a syncronized manner to use the Hall Sensor for positioning, that is why the sensored motors are supposed to be more efficient, as there are specific hall sensor for positionining leaving the winding fully usable at all times, in any cas I did measure voltage on all three wires, about 4V max on each one on a 3S setup.

I wish a manufacturer of ESC's will actually give some explanation of it, but looks like the inverters in the ESC change the frequency along with the voltage to control the motor speed and using a winding to determine the position of the rotor so it can synchronize the rotating magnetic field and in this way the timing can be set by changing the advance of the rotating magnetic field in relation to the rotor. This is the way I knew it worked, but again, somewhere I read about being DC the way I said before, but right know stand with this latest statement as I just performed the check in house.

Regards
Did you use an oscilloscope or a multimeter to make your measurements?

Regards,
Jason.
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Old 08-16-2012, 05:44 PM
  #263
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Default RE: F3A Results - SPOILER

Multimeter, with Hz measurement, don't have a Oscilloscope at home, but for looking at it in a Oscilloscope will give conclusive results.
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Old 08-16-2012, 07:36 PM
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Default RE: F3A Results - SPOILER

Historically AC or alternating current implies a change in polarity. There is no change in polarity in our brushless motors. However, if you were to look across the windings you would see a voltage with a DC level and with a ripple at the switching frequency. Electronics guys call this ripple AC (the alternating current) even though there is no change in polarity. So.... who cares what we call it?

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Old 08-17-2012, 05:06 AM
  #265
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Default RE: F3A Results - SPOILER

Jim,

Exactly, that is what I measure on the first ESC, but not yesterday, very confusing, as DC reading was only mV, where across the fields I measured 4VAC.
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Old 08-17-2012, 05:50 AM
  #266
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Default RE: F3A Results - SPOILER

Well, as the original post of the question (whether our motor is AC or DC), I was confused as well.

Here is a good article explaining the guts of how a brushless motor is driven: ftp://ftp.ni.com/pub/devzone/tut/dcvsacbrushless.pdf.

The bottom line is how the ESC applies the current to the three motor wires at any point of time. In one scheme (ref to section "DC control/phase–phase connected motor"), the current direction in one wire can change over time, which is very similar to AC current!
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Old 08-17-2012, 12:35 PM
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Quote:
ORIGINAL: nonstoprc

Well, as the original post of the question (whether our motor is AC or DC), I was confused as well.

Here is a good article explaining the guts of how a brushless motor is driven: ftp://ftp.ni.com/pub/devzone/tut/dcvsacbrushless.pdf.

The bottom line is how the ESC applies the current to the three motor wires at any point of time. In one scheme (ref to section ''DC control/phase–phase connected motor''), the current direction in one wire can change over time, which is very similar to AC current!
If you look at how a DC motor works you will see that current flows in both directions (reverses) through the windings during one rotation. However the voltage/current supplied to the motor is DC. DC motors come as brushed, brushless and steppers which are a type of brushless.

Jim O
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Old 08-17-2012, 02:24 PM
  #268
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Default RE: F3A Results - SPOILER

The ESC actually changes the direction of the current over time, as explained in the document.

There is no brush involved. The motor is driven by o/off of the voltage and the direction of the current with high frequency. The later would imply a change of the polarity of the voltage.
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Old 08-17-2012, 11:40 PM
  #269
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Default RE: F3A Results - SPOILER


Quote:
ORIGINAL: nonstoprc

Well, as the original post of the question (whether our motor is AC or DC), I was confused as well.

Here is a good article explaining the guts of how a brushless motor is driven: ftp://ftp.ni.com/pub/devzone/tut/dcvsacbrushless.pdf.

The bottom line is how the ESC applies the current to the three motor wires at any point of time. In one scheme (ref to section ''DC control/phase–phase connected motor''), the current direction in one wire can change over time, which is very similar to AC current!
Thanks, that was worth the read even though I hate National Instruments LabVIEW products with a passion.

Just to satisfy my own curiosity now I'll have to grab a powerscope and find out what my CC85hv is pushing down the wires of a motor.
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