Motor Book

4. Standards for for AC motors IEC 60034

Electrical tolerances Electrical tolerances cover allowable tolerances for efficiency, power factor, speed, locked-rotor torque, breakdown torque, locked-rotor current and moment of inertia

Parameter

Tolerance

Efficiency Machines P < 50 50 kW kW

-15% (1-η motor)

Machines P > 50 50 kW kW

-10% (1-η motor)

Power factor

-1/6 (cos phi)

Breakdown torque

   e    u    q    r    o     t     d    a    o     l       l     l    u     F     %

Locked-rotor torque Full-load torque

Pull-up torque (PUT)

(Min 002; Max 007) Slip

% Synchronous speed

Machines P < 1 kW

+/- 30%

Machines P > 1 kW

+/- 20%

Lock Locked ed-r -rot otor or tor torqu quee

- 15%, 15%, +25 +25% % of gua guara rant ntee eed d torq torque ue

Locke ocked d-rot -rotor or cur current ent

+20% +20%

Speed/torque curve for an AC motor Tolerances are defined in IEC 60034-1

Not stated in connection with Grundfos motors The locked-rotor torque defines the pull-up torque Pull-up torque

The locked-rotor torque represents the minimum torque for single and three-phase MG and MMG motors during acceleration The pull-up torque for pole-changing motors (Dahlander) is smaller than the locked-rotor torque

Breakdown torque

-10% of the guaranteed torque if the break-down torque > 15 full-load torque

Grundfos Motor Book 51