This paper analyzes the maximum torque per ampere vector profile at steady-state and transients for different interior permanent magnet synchronous motors. A detailed analysis of torque and power versus current functions is performed at steady-state, showing that a technique based on minimization of input power versus current can be used to tune the control system, thus avoiding any torque measurement. Moreover, the paper analyzes the torque evolution under maximum torque per ampere control strategy, on motors with different characteristics. Useful modifications in the current loop are suggested to improve the drive performance. Experimental results confirm the theoretical analysis, showing the benefits of the new control schemes.