Torque full-load

Starting Torque Full Load Amps NEMA Code Letter —Frame ... 

During a run, if the supply voltage to a motor terminal drops to 85% of its rated value, then the full load torque of the motor will decrease to 72.25%. Since the load and its torque requirement will remain the same, the motor will star to drop speed until the torque available on its speed-torque curve has a value as high as 100/0.7225 or 138.4% of T to sustain this situation. The motor will now operate at a higher slip, increasing the rotor slip losses also in the same proportion. See equation (1.9) and Figure 1.7. 

Judicious electrical design will ensure a pull-out torque slip as close to the full-load slip as possible and minimize the additional slip losses in such a condition. See Figure 1.8. A motor with a pull-out torque as close to full load slip as possible would also be able to meet a momentarily enhanced load torque during a contingency without any injurious heat or a stalling condition. 

The current in the copper ring opposes the main flux in that area of the pole and behaves like an artificial second winding, and develops a rotating field. Although the torque so developed is extremely low, it is enough to rotate such small drives, requiring an extremely low starting torque, of the order of 40-50% of the full load torque. 

Tj = rated or the full-load torque and should occur as near to the synchronous speed as possible to reduce slip losses. 

When the torque is determined by the above method, the voltage during the test should be so adjusted that the locked rotor current is approximately equal to the full load current. After the locked rotor test, the resistance of the stator windings should be measured and may also be considered for calculating the I R losses. 

Minimum locked rotor torque percent of full load torque... 

Torques in Percent of Motor Full-Load Torque... 

Torque is the turning effort developed by the motor or the resistance to turning exerted by the load. Usually torque is expressed in ft-lb however, the usual expression is as a percentage of the full load torque. Synchronous motors usually offer several types of torque. Starting or breakaway (called locked rotor) torque is developed at the instant of starting, see Figure 14-12. 

Full-load torque The torque necessary to produce the rated horsepower at full load speed. In lb at 1 ft radius, it is equal to the horsepower X 5,250 divided by the full load speed. 

The pull-out or breakdown torque must be greater than the maximum torque required by the driven equipment to prevent stalling, usually 150% of full load torque for unity-power fector motors and 220-225% for 0.8 leading power factor motors. ... 

Starting with full load, or unloaded. . . If unloaded by what means . For variable-speed or multi-speed drives, is load variable, torque,... 

D. Performance characteristics. (Usually includes following electrical characteristics efficiency, power-factor, locked rotor KVA, fullload speed, temperature rise and starting, break-down, and full-load torques.) Be sure to advise whether special test certification is to be furnished this always extends delivery time and increases cost. 

Values are expressed in per cent of full-load torque and represent the upper limit of the raiif e of application. 

With an adjustable voltage supply to the armature, at speeds below basic, the motor is suitable for a constant-torque drive. Minimum speeds are limited by temperature rise, because the motor carries full-load current at the lower speeds and at low speeds... 

From no load to full load, the drop in speed of compound-wound motors is approximately 25%. Compound-wound motors are used where reasonably constant speed is required and for loads where high starting torque is needed to accelerate the drive machine. 

FULL LOAD TORQUE MOTOR PROTECTION TYPE 40... 

FULL LOAD TORQUE MOTOR TEMP CLASS 39... 

STARTING TORQUE PERCENT FULL LOAD AMPERES ... 

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