How to choose a transformer?

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Annaa

Banned
Location
New York
There is a new coal washing plant, mainly using electric equipment three-phase asynchronous motor, with a total rated power of 300kw.
Working 16 hours a day, how many transformers should I choose? Is there a detailed calculation formula?
Should we consider active power, reactive power, and the load factor of the transformer, the guarantee factor, and the loss?
Please familiar friends, give pointers! ! Thank you! !
 
There is a new coal washing plant, mainly using electric equipment three-phase asynchronous motor, with a total rated power of 300kw.
Working 16 hours a day, how many transformers should I choose? Is there a detailed calculation formula?
Should we consider active power, reactive power, and the load factor of the transformer, the guarantee factor, and the loss?
Please familiar friends, give pointers! ! Thank you! !
Seriously, is this a joke? You post about Coal in the PV forum. You give hardly any details. How about seeing if the utility will serve you at the voltage the motor requires so you dont need transformers :slaphead:
 

Besoeker

Senior Member
Location
UK
There is a new coal washing plant, mainly using electric equipment three-phase asynchronous motor, with a total rated power of 300kw.
Working 16 hours a day, how many transformers should I choose? Is there a detailed calculation formula?
Should we consider active power, reactive power, and the load factor of the transformer, the guarantee factor, and the loss?
Please familiar friends, give pointers! ! Thank you! !
As a rule of thumb, I've based it on load kVA plus 20%. But mine have usually been based on our variable speed drives they fed.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Transformers are typically rated in kVA not kW.

I'd be inclined to look at the maximum kVA load the system will see and then add some fudge factor (20% is as good as anything) and then pick the next standard size up transformer.

I'd make sure though that if you have a large motor that is a big chunk of the total load that the power system and transformer together can supply enough starting current. This is not usually an issue since larger HP motors are normally required to have some kind of soft starter so the starting current is much reduced.
 
Interesting, both EEs factor in 20%, which is 80% loading.

Empirical knowledge, I assume, but it actually incorporates the same value as considering the load as continuous.

Coincidence?
Im not an EE, but my take: if the transformer is serving lots of snall/general loads, some fudge is probably good for non perfect balancing, power factor, and future loads. If it's a single dedicated motor load, I see no need for fudge since the nec FLA are already very conservative, and most motors will not be used at their nameplate power.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
Since the OP hasn't been back to explain his question a little better this one is closed.

Roger
 
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