Permanent-magnet synchronous motors (PMSM) are widely used in industry, transport and household appliances due to many advantages such as high power and payload, maintaining a constant speed at impact loads and voltage fluctuation, and high efficiency. Implementation of sensorless algorithms instead of measuring equipment may reduce the cost price of systems with PMSM. Field-oriented PMSM control requires information on rotor position and speed. Sensorless control methods replace the measured rotor position and speed with their estimates. The estimates are supposed to be obtained from the measured electrical quantities such as the motor voltages and currents. This paper continues the trend of sensorless control design and is devoted to design of rotor speed, position and flux observers for PMSM. The problem is solved under assumption that winding resistance, inductance and viscous friction coefficient are known; load torque is known or measured. In this paper the classical stationary reference frame model of the nonsalient PMSM is used. A simple speed observer is designed using linear filtration of known signals. The necessary condition for the convergence of the speed estimate is given and proved. Reparameterised model of PMSM and estimated rotor speed are used to design the position and flux observers. The proposed algorithms have simple structures and fast convergence. The theoretical results are proved by system simulation in MATLAB. Estimations of rotor speed, position and flux are conducted for different values of viscous friction coefficient and constant and harmonic load torque.