HT Motors

Because you differ from people who use delta connection?

well tried but sorry thats an uncool answer anyways

Tough.

Think about voltages and insulations. (primary)

Think about starting current (socondary) and why not go for star-delta starters (third point)

The interviews does not expect you to know, it tests (at least should had I been the interviewer) your capability to think.

Both this question as well as the other you have posted falls on same category.

Did you think the resistance/impedance of an (ideal) ammeter and volt meter. How to connect them so that even if they are exchanged nothing happens?

Under this condition which meter would read what?

Was it really difficult?

because of star connection only V/sqrt(3) apllied across one winding which reduces starting current and starting torque useful to reduce voltage dip during starting and avoid jerk in the loads on the same line

Starting torque?

The load determines the torque!

The most obvious reason is to reduce the insulation costs. With a Delta connecetion, the pahse and the line voltages are same and hence the phase to earth insultaion has to be made for the line voltage. Alternatley, with a star connection, this needs to be done only for the phase voltage, which is about 57% of the line volatge. And, believe me! the difference in cost is quite considerable.

Then, you might ask, why not this is followed in LV Motors? Wouldn't you? In LV motors, there is not much cost difference between phase voltage (240V) insulation & Line voltage (415V) insulation. If you connect the windings in delta, you have an advantage (i.e.) for the same line current (kW output), the motor windings would carry only the phase current and thus the heating in the windings would reduce by 3 times.

In LV heating cost advantage outweighs the insulation cost and in HT it is vice versa. Hope it is clear.

Hi

you can use star or delta connections in HT motors...when it is connected in Delta you motor runs stronger

Interesting concept. may I (I hope most of us) will like to know what is the meaning of when it is connected in Delta you motor runs stronger

Dear Mr.geetartha,

In HT Motors, Star Connection means Phase Voltage = Line Voltage/ Sq.Root of 3.

If 11 KV is the Supply Voltage for HT Motor, then the Phase Voltage will be 6351 Volts, i.e.6.351 KV, hence Insulation cost will be more Economical.

DHAYANANDHAN.S