Stall torque

For this example, the stall torque of the motor is 2,824 ft-lb. The runaway speed is 1,614 rpm and coincides with zero torque. The motor produces its maximum horsepower of 217 at a speed of 807 rpm. The torque at the peak horsepower is 1,412 ft-lb, or one-half of the stall torque. 

The stall torque M, (ft-lb) for any turbine motor can be determined from [86]. -5 T1hT1n,n.7 ,q tanP... 

The torque at the optimum speed is one-half the stall torque. Thus M. 

Using the basic performance data given in Table 4-110 for the 6-f--in. outside diameter turbine motor with 212 stages, determine the stall torque, maximum horsepower and pressure drop for this motor if only one motor section with 106 stages were to be used for a deviation control operation. Assume the same circulation flow rate of 400 gal/min, but a mud weight of 14 Ib/gal is to be used. 

Stall Torque. From Table 4-110 the stall torque for the turbine motor with 212 stages will be twice the torque value at optimum speed. Thus the stall torque for 10 Ib/gal mud weight flow is... 

From Equation 4-138 it is seen that stall torque is proportional to the number of stages used. Thus the stall torque for a turbine motor with 106 stages will be (for the circulation flowrate of 400 gal/min and mud weight of 10 Ib/gal)... 

As far as the remedies are concerned, an extreme option obviously exists of sizing the stem and the other parts of the valve for the maximum torque which the motor can deliver in the absence of a limiter, taking into account the non-nominal voltage, friction lower than the design one, etc. This remedy (stall torque design) is not in general practicable because of its high cost. 

Choice of gear ratio depends on the no-load speed and stall torque of the motor selected, as well as on the desired output speed and torque of the mechanism. Remember speed times torque into and out of the gear train is constant (assuming an ideal gear train). Usually, when using a dc motor,... 

Motor stall torque Induction motors can tolerate 100% stall torque indefinitely because current is shared equally by all three phases at slip frequency. A synchronous motor will require a DC current at stall, and therefore thermal capacity is reduced in both motor and inverter at stall conditions. 

A universal motor has the highest horsepower per pound ratio of any ac motor because of its abihty to operate at much greater speeds than any other 60-Hz motor. It is ideally suited for operation at a rated output, where an occasional overload or intermittent heavy load occurs. Stall torque may be as much as 10 times the continuous rated torque. The motor may even be operated in a stalled condition for short periods of time. 

The test rig aetually measures the first four items, and a eomputer ealeulates internal resistance and voltage and automatieally plots the composite curves. To produee these eurves, the brake resistance is changed from zero to the stalling torque over a period of about 10s. so the test is appropriate to short-time cranking. Tests can be elone on batteries chilled to —12. —18 or —30°C. The rig ean also be operated at a specific brake resistance to simulate the engine resistance at a specified temperature. 

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