DS18B20 for measuring Three Phase Induction Motor winding temperature

Thread Starter

fadighrayeb

Joined Oct 21, 2023
2
greeting ,

operating a 3-phase induction motor goes beyond on / off status.

these machines have a machinal parts which have its own share of Wear and tear, and it is one of the common causes of faults in bearings and occurs due to lack of maintenance and poor handling which in turn will affect the friction coefficient of bearings.

bearing sensors (vibration and temperature) commonly used to monitor and report any unusual events that has accrue.

another indicator is the motor winding temperature, especially when the motor operates with non-constant speed by using a VFD.

a PTC has been commonly used by the industry to monitor motor winding temperature

my question is:

* is it possible to use a digital sensor DS18B20 (embedded in the winding as per image below) to monitor and record the winding temperature ( 120 °C max )

* how electromagnetic induction or electromagnetic field might affect the sensor?



1697892868189.png

regards
 

liaifat85

Joined Sep 12, 2023
48
I'm afraid that you will not get the correct temperature if you use DS18B20 in a 3-phase motor winding. This is good for measuring room temperature, underwater temperature etc. Let's see if someone has used this with motors.
 

Reloadron

Joined Jan 15, 2015
7,452
Starting with the DS18B20 sensor. You are real close to the top of its range.
Measures Temperatures from -55°C to +125°C (-67°F to +257°F) • ±0.5°C Accuracy from -10°C to +85°C

During the development of a very specialized motor we did quite a bit of instrumentation on the motors. Temperature sensing and stress sensing (strain gauges). Temperature I went with small bead Type K thermocouples. Each TC assigned a location inside the motor windings generally on the end turns. This was circa 1997 and 1998. Long before the DS18B20 was around.

how electromagnetic induction or electromagnetic field might affect the sensor?
I doubt any electromagnetic field will be an issue but before putting the sensors in a motor I would just setup a few and read from them eventually expose them to a strong magnetic field and see if the readings are affected. Next, the DS18B20 sensors from China at about a buck each are counterfeit, some do work well and others not so much. Authentic sensors run about $10 each from a reputable distributor. Your call on that. My advice? Give it a try. You will know if they will work before you ever embed them in motor windings.

Ron
 

Jon Chandler

Joined Jun 12, 2008
986
Not really related....

In a past life, a client asked asked us to develop a system to measure the rotor temperature of a 104 MW hydroelectric generator. We had done this on smaller dams in the past, using thermocouples, a multiplexer and a 4-contact DIY slipping built from FR4 pcb material with carbon brushes. It actually works pretty well.

We needed about 8" of non-tapered shaft for the slip ring assembly. The shaft was tapered from the generator to the couping. The only available area was on a coupling – a coupling 7½ feet in diameter! Previously, we had only done this on shafts of maybe 3' in diameter maximum. With a little trepidation, we said we could handle end.

One thing we hadn't planned on was that the technology of adhering copper to the FR4 had greatly improved since we had last done this; we had to remove copper from between slipring tracks. Building a 24' slipring proved to be a tough process. Finally we ended up scraping the copper off with small hand planes. Ugh.

We held our breath when the turbine started with our slipring installed. Although the generator rpm was only 88, the surface speed of the slipring was far faster than any we had used before. I'm happy to say the system worked perfectly and the client asked for a second system.
 

Thread Starter

fadighrayeb

Joined Oct 21, 2023
2
Starting with the DS18B20 sensor. You are real close to the top of its range.
Measures Temperatures from -55°C to +125°C (-67°F to +257°F) • ±0.5°C Accuracy from -10°C to +85°C

During the development of a very specialized motor we did quite a bit of instrumentation on the motors. Temperature sensing and stress sensing (strain gauges). Temperature I went with small bead Type K thermocouples. Each TC assigned a location inside the motor windings generally on the end turns. This was circa 1997 and 1998. Long before the DS18B20 was around.


I doubt any electromagnetic field will be an issue but before putting the sensors in a motor I would just setup a few and read from them eventually expose them to a strong magnetic field and see if the readings are affected. Next, the DS18B20 sensors from China at about a buck each are counterfeit, some do work well and others not so much. Authentic sensors run about $10 each from a reputable distributor. Your call on that. My advice? Give it a try. You will know if they will work before you ever embed them in motor windings.

Ron
thank you very much for your delightful input , i appreciate the time you spent summarize that information for us .
i will try to expose the sensors to staitionary / moving magnet and electricalmagnatic fild and see if that will influence the readings , Authentic sensors are worth the effort with all embedded features

regards
 

Reloadron

Joined Jan 15, 2015
7,452
Not really related....

In a past life, a client asked asked us to develop a system to measure the rotor temperature of a 104 MW hydroelectric generator. We had done this on smaller dams in the past, using thermocouples, a multiplexer and a 4-contact DIY slipping built from FR4 pcb material with carbon brushes. It actually works pretty well.

We needed about 8" of non-tapered shaft for the slip ring assembly. The shaft was tapered from the generator to the couping. The only available area was on a coupling – a coupling 7½ feet in diameter! Previously, we had only done this on shafts of maybe 3' in diameter maximum. With a little trepidation, we said we could handle end.

One thing we hadn't planned on was that the technology of adhering copper to the FR4 had greatly improved since we had last done this; we had to remove copper from between slipring tracks. Building a 24' slipring proved to be a tough process. Finally we ended up scraping the copper off with small hand planes. Ugh.

We held our breath when the turbine started with our slipring installed. Although the generator rpm was only 88, the surface speed of the slipring was far faster than any we had used before. I'm happy to say the system worked perfectly and the client asked for a second system.
Thanks for sharing as I enjoyed the read. Challenges like this always make fot an interesting read. :)

Ron
 

Reloadron

Joined Jan 15, 2015
7,452
thank you very much for your delightful input , i appreciate the time you spent summarize that information for us .
i will try to expose the sensors to staitionary / moving magnet and electricalmagnatic fild and see if that will influence the readings , Authentic sensors are worth the effort with all embedded features

regards
You are quite welcome. Something to consider is when we collect data we need a place to put it. Today there are plenty of pretty good data acquisition systems built around temperature which actually chart the data. Provided only as an example. The more channels the higher the cost but when charting the data the charts can come in handy. I frequently just used a laptop.

Ron
 

Jon Chandler

Joined Jun 12, 2008
986
Thanks for sharing as I enjoyed the read. Challenges like this always make fot an interesting read. :)

Ron
Glad you enjoyed my old war story. I actually had a photo from that job on the cover of Sound&Vibration magazine, of my coworker inside the generator rotor. The work lights lit the scene perfectly and many thought it was a staged photo.

The photo was only credited "Courtesy DLI Engineering" which started a battle with management. "Credit you? Why should we have done that? The picture is a work product." Well, the picture was not taken as part of my job, not taken to document the job, taken with my camera on my film and developed at my expense. And submitted without my permission. And a simple credit as the photographer would have cost nothing and in no way diminished the value to the company.

I have worked for a few petty bosses in my career.
 
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