The torque-speed characteristics of motor $(TM)$ and load $(TL)$ for two cases are shown in the figures $(a)$ and $(b)$. The load torque is equal to motor torque at points $P$, $Q$, $R$ and $S$
The stable operating points are
- $P$ and $R$
- $P$ and $S$
- $Q$ and $R$
- $Q$ and $S$