Setting Locked Rotor Parameters

Please state the part number of the relay and the rating of the motor. The starting time of the motor is strongly related to the inertia of the load, which is very little in the case of a small centrifugal pump and bigger for a large circular saw.

• British Standard 7671 contains all the protocols needed for establishing overload and primary protection equipment selection and settings; the topic is called "co-ordination".

Hello!

The relay is an ABB relay REF 545 and the motor is 650 KW.

Besides that i saw a comment that cooldown rate should be 8.4 sec/ hour to allow one hour cooldown. But i didnt see on the relay either on motor datasheet where this one hour came from.

Regards,

Voltage?

What is it turning?

Please supply comprehensive information as it allows the forum to respond more speedily and concisely.

Hi PWSlack, I am sorry i thought only that information was enough, as i said i am starting to learn these protection settings.
The voltage is 6600V, what you mean by turning?

Pssst! She wants to know what 650kW is actually doing!!

Actually i didnt use it anywhere...

Then there is no point in energising it. Problem solved!

Dear,
i read quiclky as what is the turning?
ahh of course you solved the problem only turn off the machine

Your thread title says "Locked Rotor Parameters". In that context, none of those other issues really matter. What the relay is asking you for is the motor design limits with regard to a locked rotor condition, it would have nothing to do with load, voltage, size etc. This information can ONLY come from the motor mfr., it is not the same for any two motor designs so there are no normalized values. You need to know how long the motor can withstand a locked rotor condition, and how long it must cool off before attempting to restart it (assuming of course you have corrected the locked rotor cause). The other values that you mentioned are all about NORMAL starting conditions, this is about ABNORMAL situations.

Hi

"You need to know how long the motor can withstand a locked rotor condition"
This was passed on the stall time,

"how long it must cool off before attempting to restart" , i couldnt see on the motor datasheet nothing related to cooldown time, or warming-up time like i was seing for the other motors.
So only with these informations i am asking help cause i really dont know how to set this countdown rate only based on the parameters i wrote here and found on the datasheet. So if i have this cooldown time and warm-up , do you think i can finally solve this ?

Stall time is not exactly the same as locked rotor time. If you are running, and the motor stalls, it can be presumed that the current increased over time and EVENTUALLY the motor break Down Torque was insufficient to prevent the load from slowing the motor down to the Pull Up Torque trough, at which point it stalls. So the "Stall Time" is actually somewhat worse from a thermal standpoint than Locked Rotor, because it presumes that the motor was ALREADY running and warm, BEFORE a gradual increase in current until it stalled.

Locked Rotor Time is presumed to be with the motor cold and not already moving, so you have some time to thermally "charge" the motor mass. If you have the Locked Rotor Time values set to the Stall values, that's fine, it's just likely overly conservative. The risk is nuisance tripping on hard starting applications.

Have you tried contacting the motor manufacturer for a more detailed data sheet? That is the usual method of determining proper protection relay settings.

Hi Jraef,
I am trying to do it , awaiting on their response but anyway thanks for your help and cooperation !

No. Nonononono. Do it by telephone. It's far quicker, interactive, and one gets to talk to a real human being.