nsync = synchronous speed
f = frequency of the 3-phase power supply
p = number of pole pairs of the 3-phase motor
Kindly note that the above noted relation results in revs per second if the frequency unit is Hz.
| Pole pair numbers |
1 |
2 |
3 |
4 |
5 |
6 |
| Synchronous speed (at 50 Hz) n [rpm] |
3000 |
1500 |
1000 |
750 |
600 |
500 |
| Synchronous speed (at 60 Hz) n [rpm] |
3600 |
1800 |
1200 |
900 |
720 |
600 |
The rated full-load speed of three phase asynchronous motors is, due to slip, a few percent below the synchronous speed.
This point is called the best efficiency point (BEP) of the pump. The position of the point changes if the hydraulic parameters of the pump, such as the impeller diameter or the speed resp. the viscosity of the pumped liquid, change.
The aim of an optimal pump selection is for the pump to operate at the BEP so that it achieves its maximum efficiency.
