Frequent failing of RTDs in stator windings
Frequent failing of RTDs in stator windings
(OP)
Hello,
I am investigating a series of RTD failures in stator windings. All the RTDs are 100 ohm PT, and the motors are mostly 250 to 300 Hp. All RTDs are wired to multilin 469s. From what I have checked, the wiring is correct. All RTD failures were checked by techs. They are open circuits.
I have been working around large motors for about 15 years, and up until now I have only seen a couple of failed RTDs. With respect to this investigation, I have seen 5 failures in one year. This is in a group of about 12 motors.
I don't have a lot more info yet. I just wanted to check in advance if anyone had experience with anything similar.
thanks
EE
I am investigating a series of RTD failures in stator windings. All the RTDs are 100 ohm PT, and the motors are mostly 250 to 300 Hp. All RTDs are wired to multilin 469s. From what I have checked, the wiring is correct. All RTD failures were checked by techs. They are open circuits.
I have been working around large motors for about 15 years, and up until now I have only seen a couple of failed RTDs. With respect to this investigation, I have seen 5 failures in one year. This is in a group of about 12 motors.
I don't have a lot more info yet. I just wanted to check in advance if anyone had experience with anything similar.
thanks
EE





RE: Frequent failing of RTDs in stator windings
There are a couple of ways to read an RTD. One is to pulse it very briefly with a relatively large current that would otherwise skew the reading by self-heating but during the short reading time it doesn't. The high-ish current helps raise the measurement way above the noise. If something goes wrong that same current could cook the RTD.
Could the multilin be set up wrong?
Keith Cress
kcress - http://www.flaminsystems.com
RE: Frequent failing of RTDs in stator windings
We were primarily using GE SR489 protection relays before and after, GE claimed no change in how they managed RTD circuits, and other units installed in the same time period had no issues with the same relays.
Maybe a similar issue, not sure "value engineering" always results in a better value to the end user.
MikeL.
RE: Frequent failing of RTDs in stator windings