three phase supply Maximum demand and Diversity Quick questiion

[Richren]

Hello All, Just wondered if you have time to answer a quick question.
For maximum demand on a three phase final circuit i.e A 20 A TP-N supply. Do I have to allow 20 Amps for each phase without further calculation.

 

[D Skelton]

If the demand of a circuit is 20A, how can you apply diversity? It won't magically reduce it's demand will it.

A 13.5kW motor won't become a 7kW motor overnight

 

[davesparks]

If the load connected to the 20A final cct is 20A then you allow 20A

If the load is 18A then you allow 18A

If you have multiple similar loads with a load patten which allows for some diversity then you apply diversity to that group of loads

 

[Richren]

If the load connected to the 20A final cct is 20A then you allow 20A

If the load is 18A then you allow 18A

If you have multiple similar loads with a load patten which allows for some diversity then you apply diversity to that group of loads

Sorry TP-N so if it quotes a 20A tp-n supply on plans/drawings does that mean 20a per phase=60A total loading for demand?or just 20A across all phases


or do you 400Volt*1.72*PF*I/1000

This is the information to be sent to the DNO

 

[D Skelton]

Sorry TP-N so if it quotes a 20A tp-n supply on plans/drawings does that mean 20a per phase=60A total loading for demand?or just 20A across all phases


or do you 400Volt*1.72*PF*I/1000

This is the information to be sent to the DNO

Yes, 20A per phase.

Is this homework? I'm in intrigued to know why you ask.

 

[Darkwood]

Depends what you load is as to whether diversity is applied...

Say you have a DOL 3Kw motor, the spec for the supply may be for a 20amp mcb to allow for inrush without tripping but the full load current of the motor will probably be about 6amps.

What is the load we are talking about here - very crucial to what reply we give you.

 

[Richren]

Yes, 20A per phase.

Is this homework? I'm in intrigued to know why you ask.

Hi yes it is home work. is suppose if no real load is defined, then this is the correct prosumption.

 

[Darkwood]

Hi yes it is home work. is suppose if no real load is defined, then this is the correct prosumption.

This site is not for answering your homework questions, if you are stuck the best person is your tutor to answer your queries, we may give answers more complex and advanced than you were taught and only aid to confuse you, also been given the answer has little gain for your education and may mean in the real world you will be ill prepared and find yourself quickly out of your depth.

Request access to the trainee forum where you can discuss with like minded trainees who are doing the same courses as yourself.

 

[Richren]

Depends what you load is as to whether diversity is applied...

Say you have a DOL 3Kw motor, the spec for the supply may be for a 20amp mcb to allow for inrush without tripping but the full load current of the motor will probably be about 6amps.

What is the load we are talking about here - very crucial to what reply we give you.

I do not tknow the load to be connected, this is homework. May i ask if you were to know the load would you allow for the inrush current in the diversity. many thanks

 

[Richren]

This site is not for answering your homework questions, if you are stuck the best person is your tutor to answer your queries, we may give answers more complex and advanced than you were taught and only aid to confuse you, also been given the answer has little gain for your education and may mean in the real world you will be ill prepared and find yourself quickly out of your depth.

i am sure i would be ok, i hate lower level education ehich is why i am asking people that hopefully know the real reality. many thanks for your time.

 

[Darkwood]

I do not tknow the load to be connected, this is homework. May i ask if you were to know the load would you allow for the inrush current in the diversity. many thanks

Check my edit to last post for best place to discuss this, in the main forum we are more advanced and your question has too many possible variables to give a one answer solution, when you fill out DNO supply upgrades or new install the paperwork you fill in asked many questions including rating of largest motor, frequency of starting etc ... so the answer will be far more advanced than your course work has taught you, this is why we don't help with homework in the main forum so ask for access to the trainee section from one of the moderators.

 

[trev]

If the demand of a circuit is 20A, how can you apply diversity? It won't magically reduce it's demand will it.

A 13.5kW motor won't become a 7kW motor overnight

Unless you have a magic voltage optimisation thing.
See, caught you there mate