Measure Motor Windings temperature

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goodoboy

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Hello,

I have a 460HP motor, is there a way to measure the motor windings (or internal motor temperature)?

I got a motor that is off majority of the time in a high condensation area, and I want to makes sure my space heater is keeping the internal motor temperature above the outside ambient temperature to prevent windings decay over time.

Thank you kindly.
 
RTDs can be installed in the windings to monitor winding temperature. But it is important to install the correct RTDs in order to obtain the correct data. I would contact the motor manufacturer and have them recommend the correct RTDs to be installed.

Attached is some information that I believe you will find helpful.
 

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electric_cal said:
RTDs can be installed in the windings to monitor winding temperature. But it is important to install the correct RTDs in order to obtain the correct data. I would contact the motor manufacturer and have them recommend the correct RTDs to be installed.

Attached is some information that I believe you will find helpful.
Click to expand...

Thank you , I appreciate it.

I am basically looking to monitor via a temp transmitter the motor windings and compare these readings to ambient temperature to make sure my space heaters are performing correctly.
 
If the motor is in fact off, then you can use the resistance of the windings to determine their temperature. See "resistance method" in this article http://www.leeson.com/TechnicalInformation/hottopic.html

Essentially you are using the winding itself as a huge copper RTD.

Note that you would need a very accurate micro-ohm meter to determine winding temperature correctly, and you would also need to establish a baseline resistance, meaning you would need to know the temperature of the motor in the first place. Also this method gives you the average temperature of the winding, and won't tell you if part of the winding is too hot and another part too cold.

IMHO embedded RTDs would be a more practicable approach to getting the temperature measurement you want.

-Jon

(Note: the above in response to my read that you want to use the windings themselves as your temperature probe. If this is not what you want to do, then please disregard.)
 
Since the goal is to check the performance of the heaters, just putting the RTD inside the motor housing, in thermal contact with a winding should be plenty good.

Sent from my XT1080 using Tapatalk
 
I'm only going to throw out a Google search

nema motor temperature measuring

At the bottom of the first page is four manufactures of motors and how they see and use measuring.

Once you see an aspect of measuring that you like just Google again for manufactures of a,b,c...
equipment.

Hope it helps...
 
petersonra said:
you can buy motors that have RTDs embedded in them.
Click to expand...

Please note that the embedded RTDs are used to protect the motor against overheating as a more accurate way to protect the motor than current based overload protection alone. It also allows the motor to be operated closer to the high end safety margin than current -based protection alone.

The RTD monitoring may not as responsive to condensate prevention monitoring as one would like as there is a temperature latency between the outside of the winding - where the condensate occurs - and the inner core of the winding.

I recommend flexible space heaters strapped against both ends of the stator winding and then current monitoring on each. The most common problem being with the older type space heaters - little cartridge elements in a perforated housing - that they 'burn out' and fail to provide the heating that is desired. Burn-out used to be a fairly common occurrence with the old rigid space heaters, but the newer types are flexible, made of silicone material, operate at a lower temperature and directly attach to the end-turn heads of the winding. They are similar to heat tracing cables.

Current monitoring - with a small relay - allows you to 'know' not only that it is working but to alert you to when it is open and you need to replace it. The replacement cost will be a shocker though because you need to disassemble the motor and that adds to the cost of the heater easily in a multiplier of double digits. (I usually spec my large motors with dual space heaters, so when one 'burns' out I just have the other as a standby spare.)
 
Or, just use one of these Motor Winding Heaters, which tracks the resistance for you and applies the power needed to keep it warm enough through the existing motor power leads, heating it from the inside out rather than from the outside in with space heaters.
Example*:
1322049.jpg
http://www.ab.com/en/epub/catalogs/12768/229240/229258/229579/Introduction.html

If you are using a soft starter or VFD, check to see if it has this sort of feature built-in as well, some do.

*(Full disclosure; this is from my employer, albeit a different division, but there are others available)
 
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