Hot/Cold ratio

[Vegemite]

I am trying to protect an 11 kV, 50 Hz, 2 MW, Alstom Cegelec squirrel cage induction motor built to IEC standards with an electronic motor protection relay which wants the hot/cold ratio entered.

I know the motor is rated for 2 cold starts and 1 hot start, has a thermal time constant of 33 minutes and has a locked rotor time (cold?) of 9 seconds.

From this data can I make an approximation of the hot cold ratio?

 

[aolalde]

If you provide the complete relay details, probably someone be able to identify the hot/cold ratio requirement.

 

[rbulsara]

what does the relay manual say? Also speak to technical support of the relay mfr.

 

[jraef]

John,
Here is an excerpt from the Multilin 469 manual.
"The HOT/COLD CURVE RATIO may be determined from the thermal limit curves if provided or the hot and cold
safe stall times. Simply divide the hot safe stall time by the cold safe stall time. If hot and cold times are not provided,
there can be no differentiation and the HOT/COLD CURVE RATIO should be entered as "1.00"."

Hope that helps.

"Venditori de oleum-vipera non vigere excordis populi"