motor insulation temperature rise
motor insulation temperature rise
(OP)
What is the difference between motor 'Measurement of Temperature Method' when designated on motor data sheet as 'resistance' vs. 'RTD'? I understand that the RTD method of testing will better eliminate possible hot spots in the windings of a new motor.





RE: motor insulation temperature rise
An RTD has a well defined characteristic from which there is minimal variation due to manufacturing so a system using an RTD is capable of a fairly high level of accuracy 'out-of-the-box'. Thermistors have a greater manufacturing tolerance around the nominal response, so the overall measurement is less accurate unless the instrument is calibrated for a specific thermistor.
Both methods can only measure the temperature at the point they are measuring, so both methods rely heavily on the choice of location and the installation method to provide protection.
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Sometimes I only open my mouth to swap feet...
RE: motor insulation temperature rise
RTD method is reading the temperature with the RTDs (usually permanent) in the windings.
It's been a while though for me. I think RTD method is preferred.
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This is normally the space where people post something insightful.
RE: motor insulation temperature rise
Could well be.
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Sometimes I only open my mouth to swap feet...
RE: motor insulation temperature rise
*Nothing exists except atoms and empty space; everything else is just an opinion*
RE: motor insulation temperature rise
RTDs only measure the temperature where they are! On the large (1000+ kW) I used to be involved with, we put them in the slot separator, that is the strip of insulation between the top and bottom layers of the winding. That is the place you expect to be the hottest. As they were about 10 to 20cm long, they will again only measure the average.
RE: motor insulation temperature rise
Since resistance method gives average winding temperature, and ETD method - (theoretically) temperature in hottest poits of the winding, for the latter method limits of temperature rise are higher by 5-10 K (depending on machine output, acc.to IEC60034-1).
Acc to a/m IEC standard: "In general,(...) the resistance method (...) shall be applied (...)"; however, with several exceptions, eg. for machines of output 5 MW(MVA) and more the ETD method shall be used.
(ETD=embedded temp.detector is more general term, and acc.to IEC it can include not only RTD(as Pt100) but also thermocouples etc.).
ETD (RTD) method is much more practical to use in practice (to monitor winding temperature during machine's operation).
RE: motor insulation temperature rise
RE: motor insulation temperature rise
RE: motor insulation temperature rise
During the factory 'Method of Temperature Measurement' when using the RTD method are they using the (if specified & purchased)permanent embedded RTDs 2 per phase winding during the test or are they installing temporary RTDs for the test temperature rise measurement? The resistance measurement is clear.
RE: motor insulation temperature rise