Magnetic Field Sensor for Synchronous Servo

Thread Starter

halahelmi

Joined Jan 17, 2023
4
I need to know if there is any possible way to calculate the load for a synchronous servo motor without having the exact current and voltage. Having a magnetic field sensor and using FFT analysis
 

nsaspook

Joined Aug 27, 2009
13,272
It would be very motor specific and a experimentally derived value unless the sensor was directly in the main motor drive flux.

1673966881582.png
Where would this sensor be located at?
 

nsaspook

Joined Aug 27, 2009
13,272
Thanks for your reply. The sensor attached to the surface of the motor
I hope you can access this.
https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9751442
Study on the Peripheral Magnetic Leakage and Shielding Measures of Surface-mounted Permanent Magnet Motor*
2 Magnetic circuit model
The external magnetic flux leakage of the motor is
very low compared to the main magnetic flux of the
motor, and the attenuation is very fast due to the low
permeability of air [23]. The external magnetic flux
returns to the stator core after passing through the
rotor core, PM, working air gap, stator core, and
external air. The path is shown in Fig. 1

...
3.1 Different loading conditions When the motor has a rated load, the direction and value of its magnetic induction strength greatly vary depending on the spatial position. Different measuring circles are set around the motor, and its magnetic induction intensity is shown in Fig. 7.
...
To compare different load conditions, the same measurement position is set when the motor has no load, and the maximum average value is taken. The magnetic flux leakage value of the motor in the two load conditions is shown in Fig. 8. From the perspective of the results, the magnetic flux leakage shows a nonlinear distribution. Fitting the curve in Fig. 8, the following equations can be obtained
...
The magnetic flux leakage at
the no-load condition is obviously larger than that at
the full-load condition, at approximately 1 order of
magnitude.
Many of the modern motors are magnetically shielded making reliable readings difficult from the surface.
 

Thread Starter

halahelmi

Joined Jan 17, 2023
4
Many thanks nsaspook for your time, support and effort. I want to ask about If I have accumulator sensor can It be used to detect or determine and calculate the load
 

Ya’akov

Joined Jan 27, 2019
9,164
Welcome to AAC.

It would be far better to attach the sensor to the power supply line at the motor rather than the housing. It would be trivial to calculate current (and extrapolate load for a motor you’ve characterized) and it is equally non-invasive, can be done in the same location as a sensor on the motor’s housing.

Without a rationale for putting it on the housing instead of the power supply line, I would have to say the housing makes no sense given the proximity of the other location and the simplicity of using it.
 

Thread Starter

halahelmi

Joined Jan 17, 2023
4
Thanks so much for the informative reply, Ya’akov
Just to make sure I understood right I should place the accumulator sensor or the manometer in the power supply line? and how it will collect the data ?
 

Ya’akov

Joined Jan 27, 2019
9,164
Thanks so much for the informative reply, Ya’akov
Just to make sure I understood right I should place the accumulator sensor or the manometer in the power supply line? and how it will collect the data ?
When current flows in a wire a magnetic field forms at right angles to the current flow proportional in strength to the amperage. This is the method used for DC clamp type ammeters and other DC current sensors.

If you know the load vs. current curve of your motor, you will be able to use the derived current measurement to determine the load.
 
Top