To determine whether a transformer is single-phase or three-phase, you can consider the following factors:
Number of input and output lines
Single-phase transformers usually have two input lines (one hot and one neutral) and two output lines (also one hot and one neutral). On the other hand, three-phase transformers have three input lines (typically labeled L1, L2, and L3) and three output lines.
Voltage configuration
Single-phase transformers are typically used for low voltage applications, such as residential and small commercial buildings, where the voltage requirement is single-phase (e.g., 120V or 240V). Three-phase transformers are employed in industrial and large-scale commercial settings, where the voltage demand is three-phase (e.g., 208V, 480V, or 600V).
Physical characteristics
Single-phase transformers are generally smaller and lighter compared to three-phase transformers. Single-phase transformers often resemble a rectangular box with two input terminals and two output terminals. Three-phase transformers, on the other hand, are typically larger and heavier, and they have three sets of input and output terminals.
Nameplate information
The nameplate attached to the transformer usually provides important details about its configuration. Look for information such as the input voltage, output voltage, kVA rating, and phase designation. If the nameplate mentions a single voltage value (e.g., 240V) without any reference to multiple phases, it is likely a single-phase transformer. If it lists multiple voltages (e.g., 208V/120V), it is typically a three-phase transformer.
