Voltmeters
A simple DC voltmeter can be constructed by placing a resistor (RS), called a multiplier, in series with the ammeter
Moving Iron Vane Meter Movement
The moving iron vane movement (Figure 1) can be used to measure both AC current and voltage. By changing the
Electro-Dynamo Meter Movement
The electrodynamometer movement (Figure 1) has the same basic operating principle as the D’Arsonval meter movement, except that the permanent
D’Arsonval Meter Movement
The most commonly used sensing mechanism used in DC ammeters, voltmeters, and ohm meters is a current-sensing device called a
Classification of Transformers
Transformers are constructed so that their characteristics match the application for which they are intended. The differences in construction may
Transformer Coil Polarity
The symbol for a transformer gives no indication of the phase of the voltage across the secondary. The phase of
Transformer Operation Under No-Load
If the secondary of a transformer is left open-circuited (Figure 6), primary current is very low and is called the
Transformer Losses and Efficiency
All transformers have copper and core losses. Copper loss is power lost in the primary and secondary windings of a
Three Phase Transformer Connections
So far, our discussion has dealt with the operation of single-phase transformers. Three-phase transformer operation is identical except that three
Transformer Current Ratio
The current in the windings of a transformer is inversely proportional to the voltage in the windings. This relationship is