Voltmeter and Selector Switch Connection for Three (3) Phase Supply

Hey, in this article we are going to see the wiring diagram and connection between the voltmeter and selector switch for three-phase voltage measurement. Some selector switches provide the function for voltage measurement between phase terminals only but here we have used a selector switch through which we can measure voltage phase and neutral terminals. Here, we can measure voltage between Line to Line terminals and Line to Neutral terminals so we can measure six different voltages such as L1-L2, L2-L3, L3-L1, L1-N, L2-N, and L3-N. You can see this type of arrangement in industrial panels, three-phase systems, automatic voltage regulator circuits, etc.

Equipment Required

1. Three Pole MCB
2. Voltmeter Six Position Selector Switch
3. Voltmeter up to 600V Range.

Wiring Diagram and Connection

Here, you can see the wiring diagram and connection between the voltmeter, selector switch, MCB, and Power supply.

Connection Procedure

1. Connect all three phases or line terminal to the input of the 3 poles MCB. Before connecting identify the input and output terminals of the MCB. Here, the MCB has input terminals at the top side your MCB may have input terminals at the bottom side.
2. Now connect the Output terminals from the MCB to the selector switch. Connect L1 or R Phase terminal to the L1 terminal of the switch. Connect L2 or Y phase terminal to the L2 terminal of the switch and Connect the L3 or B Phase terminal to the L3 terminal of the switch.
3. Connect the neutral terminal of the power source directly to the 'N'(Neutral) terminal of the selector switch.
4. Now, connect the V1 and V2 terminal of the selector switch to the voltmeter.

Operation

1. When the switch is kept in the OFF position the voltmeter will not show any voltage.
2. When we rotate the switch to the L1-L2 position the voltmeter will show the voltage between L1 and L2 terminals or R and Y Phases.
3. When we rotate the switch to the L2-L3 position the voltmeter will show the voltage between L2 and L3 terminals or Y and B Phases.
4. When we rotate the switch to the L3-L1 position the voltmeter will show the voltage between L3 and L1 terminals or R and B Phases.
5. When we rotate the switch to the L1-N position the voltmeter will show the voltage between the L1 and Neutral terminals or R phase and neutral.
6. When we rotate the switch to the L2-N position the voltmeter will show the voltage between the L2 and Neutral terminals or Y phase and neutral.
7. When we rotate the switch to the L3-N position the voltmeter will show the voltage between the L3 and Neutral terminals or Y phase and neutral.

Working Principle

The selector switch makes and breaks two contacts every time when we rotate the switch. For example, when we rotate the switch at the L1-L2 position the switch will make contact between two output terminals with the L1 and L2 terminals. Now, when we rotate the switch at the L2-L3 position the switch breaks its old contacts and makes new contact to connect the output terminals with L2 and L3 terminals. Thus all the switching function works.

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