Help! Brushless Motor running BACKWARDS - RC Groups
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Jul 02, 2005, 02:51 PM
Checking the wind
kansascloud's Avatar

Help! Brushless Motor running BACKWARDS


Please help! I'm installing a Balsa Products BP 21 on my Slow Stik. (my first burshless setup) I'm also using the BP 18 amp esc. I installed all new deans conectors making very sure everything is white to white and red to red. Everything works great but the damn thing runs backwards!!!

What do I do?

Thanks for your help!

Mike
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Jul 02, 2005, 02:55 PM
Registered User
Quote:
Originally Posted by kansascloud
Please help! I'm installing a Balsa Products BP 21 on my Slow Stik. (my first burshless setup) I'm also using the BP 18 amp esc. I installed all new deans conectors making very sure everything is white to white and red to red. Everything works great but the damn thing runs backwards!!!

What do I do?

Thanks for your help!

Mike
Just swop any two motor to esc wires.

Make it red to white and white to red and leave the other one alone

Do NOT swop the battery to esc wires or it will be toast
Jul 02, 2005, 03:30 PM
PGR
PGR
Low AltiDude
PGR's Avatar
Quote:
Originally Posted by raymcm
Just swop any two motor to esc wires.
Yup! A brushless motor doesn't know "backwards" or forwards. It only knows clockwise and counterclockwise and it doesn't prefer either one. To change rotation, simply switch any 2 of 3 wires between motor and ESC.

It's intresting to note that you change the rotation of industrial 3-phase motors the same way.

Pete
Jul 02, 2005, 04:49 PM
Registered User
Brushless motors are 3 phase AC motors, exactly the same as Industrila 3 phase AC motors. The controller converts from DC to AC.
Jul 03, 2005, 12:32 PM
Destroyer of Cell's!!!
nasa_steve's Avatar
can i just jump in here the brushless esc is actually pulsed DC and not true AC in my knowledge of the subject the esc merely mimics AC and does not acually make it
regards
nasa
Jul 03, 2005, 12:52 PM
Marion
The only diference, seems to me, is that the ESC makes three phase square waves, and your house current is sine wave. Right ?? The ESC output is still AC in my book.

Marion
Jul 03, 2005, 01:08 PM
Destroyer of Cell's!!!
nasa_steve's Avatar
hi marion
no believe me i am by trade an electrician and pulsed dc is definately not ac. in an ac supply there is both positive and negative within the supply. dc is direct with no negative element in the supply. pulsed dc is literally supply on supply off. ac is not switched it moves to positive and then negative by equal amounts hence the sine wave output on an oscilloscope the baseline on the ac output is is in the middle on a dc output it is at the bottom.
hope this clarifies a bit i can go further but then you'd end up being bored silly by the science.
regards
nasa
Jul 03, 2005, 01:27 PM
I don't want to "Switch Now"
pmackenzie's Avatar
Since Mike's question has been answered, I will dive in here as well.
Motor terminology is not carved in stone, but is by convention.

The vast majority of industrial motors are 3 phase AC induction motors. No magnets, only coils. Completely different animal.
They always spin slightly slower than the rotating field. Higher load results in lower speed, but the input frequency is always the same.
Single phase induction motors are an offshoot of the 3 phase ones.

Another type of industrial motor is the 3 phase synchronous motor. It is normally made with slip rings and field coils in the rotor, where we use permanent magnets.
They always spin at the same frequency as the AC field.
As load is applied the phase angle between the rotating field and the motor increases increasing the torque.

The closest thing to a DC brushless motor is the AC servo motor. The construction can be almost identical.
What is different is the driving circuits. They generate pseudo sine waves.
Torque is controlled by the phase of the sine wave relative to the motor rotation, just like the AC synchronous motor. This is called vector control.

Brushless DC motors vary the torque by varying the applied voltage only.
The phase is held fixed either by the sensors or by the sensorless controller. The waveforms are not pseudo- sine waves, but trapezoids.
Pat MacKenzie
Jul 03, 2005, 03:29 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
Pictures of brushlesss waveforms: http://www.torcman.de/peterslrk/SPEE...l#Anker1591256


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