机械英文外文翻译一种新的电动葫芦驱动起重机

A new electric hoist drive for Cranes

A new system of electric hoist drive has been developed ,and its success has been demonstrated in practical use. For the types of hoist for which it is particularly intended this system provides a closer approach to the ideal characteristics than has previously been available. Although the system is not intended for use in all of the important types of hoist, it is expected that further experience and additional study of details and refinements will broaden its field of application beyond that which has, to date, been established in practice.

The Ideal Characteristics

Among the several hoisting applications for which the new system is believed to be suitable, the high-grade heavy-duty indoor cranes in steel mills and heavy machine shops may be considered typical. A study of the requirements indicates that the ideal characteristics for a crane of this type and of certain other types are principally as follows:

1.The same manipulation of the controller to any position in the

lowering direction should cause the motor either to deliver power for lowering an empty hook or to absorb power for the proper lowering of

a load, whichever is required by the conditions at that moment.

2.Maximum hoisting speed at empty hook should be a definite value,

approximately twice the speed at rated load.

3.At the full-speed hoisting position of the controller the stalled torque

should be limited to a reasonable overload value.

4.At the first-speed hoisting position the speed-torque curve should be

relatively flat, having a very low speed at empty hook but a substantial stalled torque.

5.The maximum lowering speed at empty hook should be a definite

selected value, between 160 per cent and twice rated hoisting speeds 6.Maximum speed of lowering rated load should be substantially less

than at empty hook, and maximum speed of lowering maximum load should be less than that of lowering rated load,

7. The minimum lowering speeds, that is, the speeds at the first

lowering-speed position of the controller should be nearly

alike .irrespective of load. If readily attainable, it is preferable that

this lowering speed be less at heavy loads than at partial loads or

empty hook.

8. The electric equipment must have in the lowering direction a

substantial margin, so that, when the maximum load which can be

lift is handled, the torque capacity available in lowering direction is ample to maintain dependable control of the load under the most

adverse conditions

9. A safe and reasonably smooth retardation and stop must occur automatically in the event of failure of incoming power and other emergencies.