We have a 2300hp 4.16kV motor whose RTD's seem to be going into alarm alot lately. The alarm is indicated on the multilin 269 protection relay with the alarm setpoint set to 135deg C and the trip setpoint set to 140deg C per the motor datasheet. Full load on the motor is 312A and the rtd's have been seen going into alarm anywhere between 285-300A. All 6 stator RTD'a are reading around the 135deg C mark.
My question is why these RTD's are going into alarm when the motor is still a little bit off from Full load current. We also have the same exact motor and application in another location here and at 280A the rtd's seem to only be around 60deg C or so.
What could be the cause of a motors RTD's running hot when it is not near full load especially when another similar motor and load has its rtd's operating at lower temps for a similar load.
This motor does have about a 5% current imbalance. Can this cause this additional heating.
Could the location of the motor play a factor. The motor is rated for a 85deg C rise in an ambient of 40deg C. If the motor is in a location that has a higher ambient temperature can the RTD's get hotter for a given load then it would see in a cooler ambient enviorment?
My question is why these RTD's are going into alarm when the motor is still a little bit off from Full load current. We also have the same exact motor and application in another location here and at 280A the rtd's seem to only be around 60deg C or so.
What could be the cause of a motors RTD's running hot when it is not near full load especially when another similar motor and load has its rtd's operating at lower temps for a similar load.
This motor does have about a 5% current imbalance. Can this cause this additional heating.
Could the location of the motor play a factor. The motor is rated for a 85deg C rise in an ambient of 40deg C. If the motor is in a location that has a higher ambient temperature can the RTD's get hotter for a given load then it would see in a cooler ambient enviorment?