Full voltage to stationary shunt motor produces very high starting current in the
armature (because the counter emf is zero) and the machine will be burnt.

All dc motors must, therefore, be provided with a starting arrangement to limit the starting current to reasonable value, usually between 1.5 and twice full-load current.

One method is to place a rheostat in series with the armature and reduce resistance as the motor accelerates. In modern practice, a starting resistor is made up of a series of pieces, each of which is removed from the motor circuit in succession as the motor speeds up, in order to limit the current in the motor to a safe value while never reducing it too low a value for rapid acceleration.

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