The electromagnetic torque expressed in (3) indicates that it can be controlled by the stator current with the torque constant, Kt. This is very similar to the control of separately dc motor drive. The load model can be expressed in terms of a moment of inertia, JL, in kg-m2/sec2 with a viscous friction BL, in N-m/rad/sec. The electromagnetic torque, Te, in N-m then drives the load torque, TL, in N-m can be expressed by