a 2 MW comisionning
a 2 MW comisionning
(OP)
again sorry for my english.... I have to do a commisioning work on a asyncronous motor of 2 Mw, 6000 V, 425 rpm... pump application, and I was worried about the times I can start it up, cause the manufaturer tell me that I can start it three times on a hour, but I think it have to be a time to cool the motor rotor specially, and then they tell me that I´ll cheeck it on the RTD of the stator, but my idea is that the rotor is the more hot part and I couldn´t measure the heat...
Any of you know some rule, as NEMA or ISO to control the number of times for the start of the motor... and how it depends on the load of the motor... in example if the motor is without load, how many times i could start it.
The amps on the starting are 450 % of the full load amps...
Any of you know some rule, as NEMA or ISO to control the number of times for the start of the motor... and how it depends on the load of the motor... in example if the motor is without load, how many times i could start it.
The amps on the starting are 450 % of the full load amps...





RE: a 2 MW comisionning
RE: a 2 MW comisionning
RE: a 2 MW comisionning
If it were me, I would tell operations a maximum of two starts per hour.
Also, a good motor protection relay can block starting based on the relay's thermal model conditions.
RE: a 2 MW comisionning
I´m not more into the relays for motor protection thing, sorry if i ask easy or stupid things....
Thanks again david
greats from Spain and maybe one day will drink a good beer under the sun and near the beach....
RE: a 2 MW comisionning
RE: a 2 MW comisionning
The relay has a software-based thermal model of the motor stator and rotor that is based on the current it senses. In the most simplistic version, it would integrate the current to give a crude estimate of heating over time. But actual thermal models are much more sophisticated than this - but not perfect. But you're right, the relay does not know exactly what is going on in the motor.
I agree that you cannot depend entirely on the stator RTDs. But some motor relays will use the RTD temperature to bias the thermal model.
RE: a 2 MW comisionning
If they say 3/hour, then they believe it can do 3 starts. There is no time limits to this. It means you can start to speed, immediate stop and then start again as soon as the motor has coasted to a stop until you have started 3 times.
If you don't trust what you have been told, then you need to decide on what you will allow. You could pick something like 2 starts per hour and 20 minutes between starts. Picking conservative numbers usually doesn't hurt anything. I'd expect you really don't need to start that often in normal operation.
RE: a 2 MW comisionning
on other hand, Lionel, the motor will not start more than one time per day, it´s a water pump.... but i´ll like to define a protection for the motor not to start more than two o three times per hour....
Thanks again