Star vs. Delta Connections

They use more power than when they are turned off 24h every day?

I think you will find that most 3 phase motors are connected in a delta configuration. So even if you have a wye service you would make a delta connection. I know that there is a disadvantage. The motor will determine your connection.

With star connection continuous operation, the copper and core material and other effective factor on machine dimensions consumption increase, instead the cost of winding insulation decrease, therefore we must balance these cost impact in design stage.

If the motor is designed to operat in star connection at your voltage and frequency, there is no disdvantage in running it in star continuously. It is designed to operate that way and you have no other choice.

If the motor is designed to run in delta at your voltage and frequency, then when you connect it in star, you are reducing the voltage across the windings by root 3 and so the flux is reduced also. Under these conditions, the effective rating of the motor is reduced to one third of the delta connection. If you run the motor continuously in star, and the load is less than 30%, there will be lower iron losses. If you run the motor in star with shaft loads higher than 30%, the motor will operat at increased slip and this will increase the slip losses dissipated in the rotor and cause excess rotor heating. - Definitely not a good idea.

Best regards
Mark.