First of all, the rated values, specified on the identification plate of the machine, must be identified. This plate may contain, in addition of the essential values, some information regarding the operation regime.

The information always present on the identification plate and necessary for determining the parameters of the equivalent diagram refer to:

• The rated power, P_N, [W], [kW], or [HP] - for a machine special designed to operate as motor, the rated power is the mechanical power, available at its shaft. For a machine special designed to operate as generator, the rated power is the electric power, available at its terminals;
• The rated voltage, U_N, [V] - for a tri-phased machine, this value is the line-to-line value. When the both ends of the stator windings are available, in order to be able to make even the connection star (Y), or triangle (D), the both values are indicated, having beside the symbol of the corresponding connection;
• The rated current, I_N, [A] - there are written two values, together with the symbol of the stator connection, if both ends of the stator windings are available. The both signify line current.
• The rated speed, n_N, [min^-1];
• Nominal power factor, cosj_N.

Rated values of the motor.

Measuring the parameters of the equivalent diagram

• 1. By using the method of the ampere-meter and volt-meter in DC, determine the stator phase resistance, for more values of the supplying voltage. As value for the stator phase voltage will be considered the average of the determined values.

• 2. Based on the results obtained at no load test, determine the magnetising inductance L_m.

• 3. Based on the results obtained at blocked rotor test, determine:
  • the rotor phase resistance, reported to the stator, R¢₂
  • the stator phase leakage inductance, L_1s (L_ss )
  • the rotor phase leakage inductance, reported to the stator, L¢_2s (L_rs )

Measuring the mechanical parameters

• 4. By using the free stop method, determine the mechanical parameters
  • the moment of inertia of the rotor, J
  • the viscous frictions coefficient, k_v
  • the dry frictions torque, t_f