Three-phase machines will always use less power and have less chance of electrical failure when compared with single phase machines. The end result being less expensive to operate than single phase in terms of power consumption, parts and service requirements.
Single-phase motors require extra electrical components, generally a start capacitor, a run capacitor and an electrical switching relay to assist in both starting the motor and running the motor. These additional components will eventually wear out causing motor start/run failure and can be even more troublesome when on a generator supply.
The rate of wear and tear leading to component failure is magnified by the number of starts and stops created each time product is drawn by a customer.
For instance, a given customer (a local yoghurt shop in Australia that has 6 x three-phase units) was showing average draw counts of 60 to 70 per 8 hours on one barrel. This means the compressor started and stopped the same number of times the handle was drawn. Multiply this by 7 days, and you have approximately 4,000 starts in one week. Multiplied by the number of trading days per year, this equals a tremendous amount of a motor workout.
The relay can fail causing a domino effect blowing the start and or run capacitor as well, leaving the machine unable to operate any further.
Three-phase motors do not use any starting electrics at all. No additional parts means less chance of breakdown and loss of customer sales as a result. This is the main reason why the largest chains in the world have always historically purchased Three-phase equipment wherever possible. Less chance of equipment breakdown combined with increased reliability translates into happy customers and good business!
Three–phase motors generally run cooler meaning they are more efficient. Three-phase motors draw less amperage or current, again supporting the fact that three-phase motors are more efficient than single phase motors. See the example below.
Motor example for both calculations is based on a 1Hp, 230V motor:
Single-phase motor is rated 8 amps. 230V x 8A = 1840 watts.
Three-phase motor is rated 3.6 amps. 230V x 3.6A x square root of 3 = 1434 watts.
So, at full load, the three-phase motor uses 22% less power to do the same work = lowest cost of operation!