This paper analyzes a method for improving transient speed deviation in single-inverter dual parallel (SIDP) interior permanent magnet synchronous motor (IPMSM) drives under transient conditions using an optimal damping current. The system injects a damping current into the d-axis of the primary motor to achieve speed synchronization between the two motors. However, the injected current can reduce system performance during transients. The additional damping current is mathematically derived to mitigate this adverse effect, which is injected into the q-axis of the primary motor. The analysis evaluates the application of the additional current to improve transient speed deviation in the drive system. The validity of the analyzed strategy is verified through simulations and experiments. Additional experimental results and detailed analysis under various operating conditions will be included in the final paper.