AS 60034.12:2009 pdf free download – Rotating electrical machines
6.1 Torque characteristics
The starting torque is represented by three characteristic features. These features shall be in accordance with the appropriate values given in table 1 or table 5. The values in table 1 and table 5 are minimum values at rated voltage. Higher values are allowed. The motor torque at any speed between zero and that at which breakdown torque occurs shall be not less than 1 ,3 times the torque obtained from a curve varying as the square of the speed and being equal to rated torque at rated speed. However, for 2-pole motors with type of protection ‘e – increased safety’ having a rated output greater than 1 00 kW, the motor torque at any speed between zero and that at which breakdown torque occurs shall not be less than 1 ,3 times the torque obtained from a curve varying as the square of the speed and being equal to 70 % rated torque at rated speed. For motors with type of protection ‘e’, the three characteristic torques shall be in accordance with the appropriate values given in table 5 NOTE The factor 1 ,3 has been chosen with regard to an undervoltage of 1 0 % in relation to the rated voltage at the motor terminals during the acceleration period.
6.2 Locked rotor apparent power
The locked rotor apparent power shall be not greater than the appropriate value given in table 2 or table 6. The values given in table 2 and table 6 are independent of the number of poles and are maximum values at rated voltage. For motors with type of protection ‘e’, locked rotor apparent power shall be in accordance with the appropriate values given in table 6
6.3 Starting requirements
Motors shall be capable of withstanding two starts in succession (coasting to rest between starts) from cold conditions and one start from hot after running at rated conditions. The retarding torque due to the driven load will be in each case proportional to the square of the speed and equal to the rated torque at rated speed with the external inertia given in table 3 or table 7. In each case, a further start is permissible only if the motor temperature before starting does not exceed the steady temperature at rated load. However, for 2-pole motors with type of protection ‘e – increased safety’ having a rated output greater than 1 00 kW, the retarding torque due to the driven load is proportional to the square of the speed and equal to 70 % rated torque at rated speed, with the external inertia given in table 7. After this starting, load with rated torque is possible. NOTE It should be recognized that the number of starts should be minimized since these affect the life of the motor.
7 Design NY starting requirements
The starting requirements are as for design N. In addition, however, a reduced retarding torque is necessary as the starting torque in ‘star connection’ may be insufficient to accelerate some loads to an acceptable speed. NOTE It should be recognized that the number of starts should be minimized since these affect the life of the motor.