
188 Electric Motors and Drives
Such motors are unlikely to be described by the maker
specifically as deep-bar, but they nevertheless incorporate a
measure of the skin effect and consequently achieve the good
torque-speed characteristic shown in Figure 6.9.
Torque, p.u. Current, p.u.
Figure 6.9 Complete torque-speed and current-speed curves for a
general-purpose industrial cage motor
The current-speed relationship is also shown in Figure 6.9,
and both torque and current scales are expressed in per-unit
(p.u.).
This notation is widely used as a shorthand, with 1
p.u. (or 100 per cent) representing rated value. For example a
torque of 1.5 p.u