ABSTRACT
In the case of motors a small allowance must be made for slip - usually 100 rev/min. As the frequency in Great Britain is 50 Hz, the maximum possible speed of a close-coupled pump unit (with the minimum of one pair of poles) is 2900 rev/min. With four poles it is 1450 rev/min, with six it is 960 rev/min, and so on. The choice of speed towards the upper limit is therefore severely restricted.
