Motor data - Specification of efficiency for motors
Example:
Motor type 080-31 (G-motion): PN = 1.1 kW, IN = 2.8 A, U = 400 V, cos = 0.82, eta = 79 % => Pmech = 1.257 kW
with M = 3.7 Nm, nN = 2810 rpm it matches: Pmech = 1.1 kW
Answer:
The efficiency is calculated from the mechanical power and the electrical data.
Electrical machines have wide manufacturing tolerances and operating conditions.
Each parameter measured under worst case conditions (for the current and the power factor) defines the rated data.
These values do not appear all together, e. g. the current is measured at the lower voltage tolerance limit (2.8 A). This value is higher than under rated conditions.
The catalogue value for the efficiency is measured at the defined rated voltage (U = 400 V). For the above example with this voltage an efficiency of eta = 0.79 is measured.
