What is selector switch for ammeter and voltmeter?Could you explain it for me?How does it work?

Question

Someone can help me ! Thank you very much !

Answer 1

The selector switch is provided for voltmeter is to check the voltage inbtween phases as well as inbetween phase and neutral.( ie ) R-Y, Y-B, B-R and R-N, Y-N and B-N. The leads of the voltage selecctor switch is direcctly connected to the the respective phase suply.
The selector switch provided for ammeter is to check the amount of current taken from each phase suply. (ie) R,Y and B. Each phase suply should be covered with a current transformer with the rated amps capacities. The two leads of the the each phase CT are connected to the respective leads in the selector switch of the ammeter.

Answer 2

The Ammeter Selector Switch - as the name suggests - is connected to an Ammeter, the purpose being monitoring of current in all the three phases (and, if needed, also in the neutral) using only one ammeter. It obviates the need to have three different ammeters for the three phass, thereby effecting saving in cost. So also, the Voltmeter Selector Switch is connected to the Voltmeter, to measure the Voltages between different phases (also, between each phase and neutal, if needed) with a single voltmeter. Here also the purpose is to save cost of two more voltmeters.

Answer 3

When using as a voltmeter resistors must be placed in series with the galvanometer. When using as a ammeter resistors must be placed in parallel with the galvanometer.