Difference between three-phase three-wire and three-phase four-wire meters

Difference: Whether to use a three-phase three-wire or three-phase four-wire meter is determined by the user’s power supply connection and electricity usage pattern. If the device is a pure three-phase appliance, such as a three-phase transformer or a three-phase motor, a three-phase three-wire system can be used. A three-phase three-wire system consists of only three wires, with no neutral wire; therefore, a meter designed for three-phase three-wire systems must be used. If a user has both single-phase and three-phase loads, it is a three-phase four-wire or three-phase five-wire (with multiple neutral and ground wires) system, and a three-phase four-wire meter should be used. Three-phase three-wire systems do not have the ability for adjustment, and it is required that the three-phase loads be roughly balanced. Difference in application scenarios: Three-phase four-wire systems have an additional neutral wire compared to three-phase three-wire systems. Three-phase three-wire systems can provide a power supply of 380 volts only, while three-phase four-wire systems can supply both 380 volts and 220 volts. Three-phase three-wire system clearly saves money, but when the load is unbalanced, it’s not possible to use the neutral wire for current return, which can lead to equipment damage; whereas the three-phase four-wire system can solve this problem

If the device is a pure three-phase appliance, such as a three-phase transformer or a three-phase motor, a three-phase three-wire system can be used. A three-phase three-wire system consists of only three wires, with no neutral wire; therefore, a meter designed for three-phase three-wire systems must be used. If a user has both single-phase and three-phase loads, it is a three-phase four-wire or three-phase five-wire (with multiple neutral and ground wires) system, and a three-phase four-wire meter should be used. Three-phase three-wire systems do not have the ability for adjustment, and it is required that the three-phase loads be roughly balanced.