Question

Which is not true for three-phase AC?
$1$. The three-phase power supply has three distinct wave cycles.
$2$. The voltage of three-phase is $230 V$ .
$3$. The efficiency of three-phase is high compared to single-phase.
$4$. Three-phase is expensive compared to single-phase.

Answer 1

Three-phase power combines the three wires to offset the highest and minimum oscillations so that a device supporting this type of power does not feel such a wide fluctuation in voltage. It makes three-phase power a very effective form of electrical power distribution. Consequently, a three-phase electric motor utilizes less electricity and typically lasts longer than a single-phase motor of the same voltage and rating.

Complete step by step answer:
The AC power is a sort of electricity when a frequent change in the current flow direction exists. The power supply system is categorized into two types: single-phase power supply and three-phase power supply. For most industrial and business settings, a three-phase supply is used to run the high loads, whereas a one-phase power supply generally supplies homes because home appliances require less power.
Generally, phase-in electricity is the current or the voltage between an existing wire and a neutral cable. Phase implies the distribution of load; if a single wire is utilized, an additional load will happen on it & if three wires are used, loads will be separated between them. This can be called less power for one-phase and more power for three-phase. The efficiency of three-phase is high compared to single-phase. Together, the three currents deliver a balanced load, something not possible with a single-phase alternating current. In alternating current, the current alternates direction, flowing backward and forward in the circuit; this means that the voltage constantly alternates, changing from maximum to minimum
The three-phase power supply comprises four wires which contain one neutral along with three conductor wires. The three conductors are at a phase angle of $120^{\circ}$ from each other. Three-phase power supplies are used as a single-phase AC power supply. The single-phase's voltage is $230V$, whereas the voltage of the three-phase is $415V$. The three-phase AC waveform is-

For the operation of a small load, a one-phase AC power supply and the neutral can be collected from the three-phase AC power system. This supply is fixed and will not be lowered to zero value. Three-phase is expensive compared to single-phase.
All options are correct for three-phase AC except (2).

So, the correct answer is “Option 2”.

Note: There are some advantages of a three-phase supply: Its equipment needs more limited copper. It tells the minimum risk for workers who are working with the system. It has a more significant conductor efficiency. It even maintains the capability to work with a long-range of power loads.