A DC machine with multi-poles can be modelled mathematically using the couple-coil theory for a healthy or a faulty machine. The model parameters are obtained from the experiments measuring the inductance on the machine using a DC source. The detailed model of a healthy DC machine is established with an assumption of varying brush resistances. All inductances for the model need to be measured under the saturated flux conditions. This model can be implemented in MATLAB for simulation. The experimental results show that the measurements of armature current waveforms, including commentator ripples, agreed quite well with the simulation waveforms from the model. The research has provided good evidence that both healthy and faulty DC machines can be modelled mathematically.