While starting a $dc$ shunt motor :
- reduced armature voltage $V_{n}$ and reduced field voltage $V_{f}$ should be applied and full regulator resistance $R_{r}$ should be included in the field circuit.
- reduced $V_{a}$ but full $V_{f}$ should be applied and $\mathrm{R}_{r}$ should be zero.
- rated $V_{a}$ and rated $V_{f}$ should be applied and $R_{r}$ should be zero.
- rated $\mathrm{V}_{a}$ and rated $\mathrm{V}_{f}$ should be applied and $\mathrm{R}_{r}$ should be maximum.