Oversizing motor conductors

[iwire]

Yes. You are correct in that the book would not know the specifics of the installation either.
But it used the superlative 'The most' i.e the most practical solution is to reduce the motor starting current. In other other words a resistance or auto transformer transformer or star-delta starter instead of DOL starter is to be used.

Neither of us can I know if reducing the motor starting cuurent is the best way to go.

And here I thought engineers wanted as much info as posible before making broad statements.

I guess you are the exception.

 

[Haji]

Neither of us can I know if reducing the motor starting cuurent is the best way to go.

And here I thought engineers wanted as much info as posible before making broad statements.

I guess you are the exception.

That broad statement was made in the book and not by me. The authors might have analyzed as much information as possible before making such a statement. But if you know any exception in practice, please let us know. Then I would be able to inform the editor of that book to incorporate your finding in the book with due acknowledgement.

 

[iwire]

That broad statement was made in the book and not by me. The authors might have analyzed as much information as possible before making such a statement. But if you know any exception in practice, please let us know. Then I would be able to inform the editor of that book to incorporate your finding in the book with due acknowledgement.

Having the transformer replaced may not take anymore than a phone call to the power company with no cost to the customer. Hard to say spending money on a fancy motor starter would make more sense to customer.

 

[Haji]

Having the transformer replaced may not take anymore than a phone call to the power company with no cost to the customer. Hard to say spending money on a fancy motor starter would make more sense to customer.

Hard to believe POCO complies with customer request to change transformer for dimming of lights in his premise. Even for persistent low voltage due to heavy load, POCO does not change to higher capacity transformer quickly. Do they?

 

[kwired]

Hard to believe POCO complies with customer request to change transformer for dimming of lights in his premise. Even for persistent low voltage due to heavy load, POCO does not change to higher capacity transformer quickly. Do they?

Really depends. Some POCO may do something 6 months later others are there same day.

Small single phase pole mounted transformers are common items for them to have in stock, if the need is there to change from say a 15 to a 25 or a 25 to a 37.5, many will do so with little or no red tape. Larger units or three phase banks, or pad mounts is a little different and higher cost is involved.

 

[Haji]

Really depends. Some POCO may do something 6 months later others are there same day.

Small single phase pole mounted transformers are common items for them to have in stock, if the need is there to change from say a 15 to a 25 or a 25 to a 37.5, many will do so with little or no red tape. Larger units or three phase banks, or pad mounts is a little different and higher cost is involved.

It is not so much about the changing of transformer by a higher size one by the POCO at the consumer request due to his lights dimming by motor start as about the unlikely poor load planning by the POCO. The competent POCO will check up the motor load of the prospective consumer against their transformer capacity before releasing the connection. If the motor starting load is too high for the transformer, the POCO would instruct the prospective consumer to provide a suitable starter to his motor. This is the rule and I do not believe the POCO violate it too often. Otherwise there would be appreciable public unrest.

 

[kwired]

It is not so much about the changing of transformer by a higher size one by the POCO at the consumer request due to his lights dimming by motor start as about the unlikely poor load planning by the POCO. The competent POCO will check up the motor load of the prospective consumer against their transformer capacity before releasing the connection. If the motor starting load is too high for the transformer, the POCO would instruct the prospective consumer to provide a suitable starter to his motor. This is the rule and I do not believe the POCO violate it too often. Otherwise there would be appreciable public unrest.

In commercial/industrial applications what you said here generally happens.

In residential and other small single phase services they change transformers like a homeowner changes burned out light bulbs - sometimes. They may not respond to customers demanding they do something about the lights dimming other than possibly checking for loose connections, but if owner has a qualified electrician determine that there may be problems on the POCO side of things then they often will put more effort into providing a solution. They do provide smaller capacity transformers than you would find installed on customer side of service point to serve a particular load, and they are aware that sometimes there will be issues with that. It is not too big of a deal for them to change a 15 kVa pole mounted transformer to a 25 kVa as these are very common stock items and they do not take that long to switch out either. Often times it is the case that the load has changed since the transformer was initially installed also.

 

[Haji]

kwired:
Thanks for your clarification.
My point is the OP not to depend on the POCO's changing their transformer for his light dimming problem: that could happen automatically because other customers would also be connected to the same transformer and would also be suffering from the same problem. If the POCO does not help immediately as seems to be the case here, the most practical solution is to provide a suitable voltage reducing starter to the motor.