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AC 3-Phase Motor (Speed Control) interfacing with AVR ATMega8535

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mrfunkyjay

New Member
Hi guys,

hello there. My name is Kelvin. I am from Indonesia and now I am working on a project to rebuild my old-fashioned Running Saw Machine for my woodworking industry.

This project supposed to use ATMega8535 as its main controller of several input and output devices but generally I am asking only about controlling the speed a 3-phase AC motor. For the typical motor I use in this project is obtained from some broken machines here so I don't plan to spend more money buying motor and inverter from the market, just want to use what I have here in my factory.

I know the basic principle of controlling a 3-phase AC motor, basically generating a frequency-based PWM signal from a DC source to act as an input to the inverter in which it will have Variable Frequency to control the speed. However, I have no experience in doing this, as well as in the commissioning section, well I don't have any idea of how I can interface these devices together.

First thing first I will share with you the type of motor I used in this project. I have one AC Servo Motor with rpm around 1500 which is suitable for this typical application. These are the procedure of the machine running:

1. Wooden board being fed into the machine.
2. Pressing plate is actuated to hold the board at still.
3. Saw is rotating by means of AC motor.
4. Saw is sliding back-and-forth to cut the wooden board.

Number 4 is the thing I need to work on. The sliding speed must be slowed down with higher torque produced by means of mechanical gearing system but the motor itself must rotate in low rpm -> that's why I choose this AC Servo Motor obtained from a broken CNC-machine by BIESSE.

Few questions here:
1. Generally, is it possible to control the speed of this servo motor by using ATMega8535?
2. Technically, I need a servopack to drive the motor but to control the motor, is this typical servopack can be fed by a DC PWM signal?

If anyone has experiences in doing what I am about to do here, please share some suggestions. I am very open to discussions because I am quite stuck in here. Thanks a lot for your support guys.

Best regards,

Kelvin Susanto
 

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pedroromanvr

New Member
Hello Kelvin:

I have experience on a BLDC motor (1kW) controller. The main idea for controlling this and the one you want (3-Phase AC Motor) is the same.

Answers to your questions:
1. Generally, is it possible to control the speed of this servo motor by using ATMega8535?
Yes, I have used that microcontroller for many applications and it can reach a PWM frequency suitable for what you want.
2. Technically, I need a servopack to drive the motor but to control the motor, is this typical servopack can be fed by a DC PWM signal?
Even beyond... you have to feed the motor with a DC PWM signal. The inherent LR filter load representing the motor will "convert" your DC PWM (for example a SPWM) into a pure sinodal electric signal.

I can recommend you to read these three application notes from atmel.
-Using feedback with Hall sensors
https://www.electro-tech-online.com/custompdfs/2011/07/doc7672.pdf
-Sensorless control (using current sensing, really)
https://www.electro-tech-online.com/custompdfs/2011/07/doc8012.pdf
-Other
https://www.electro-tech-online.com/custompdfs/2011/07/doc8010.pdf

Hope this helps!

Pedro Villanueva
 
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