The iron loss, friction, and energy of the hoist motor and the iron loss of the generator are practically zero at the moment of starting and stopping. m (16.99 oz-in) When the voltage drop and variation or load variation is thought to be . It is frequently desirable to know the no-load loss of the motor-generator set or the power required to drive the set during the rest period. If a rope of lighter weight is desired, a plow-steel rope could be used instead of the cast-steel. A circuit breaker located in the field circuit can be more readily handled than one in the main circuit. In the foregoing case, the average load, upon the motor is 450 hp. 2. The theoretical weight is estimated at 20,400 lb. Crane Weight The maximum weight of the crane to be used 50,000kgs (worst case scenario) 2. The flywheel loss is rather difficult to estimate and test results on existing wheels are rather erratic; the value of 20 hp. After the machines are determined the details of the control must be settled; this in many cases means conferences with the hoist builders to determine the details so that the electrical equipment will coordinate with the mechanical equipment supplied by the hoist builder. t = thickness of rope in inches, The Koepe system, as applied to a double-compartment shaft, has a tail-rope passing from the bottom of one cage down and around an idle sheave at the bottom of the shaft, and up to the other cage. The input when using the flywheel system is shown by the dot-and-dash line and is practically constant at a value of 578 hp. The friction is also somewhat less, being figured at 5 per cent, instead of 7 per cent, of the total suspended weight. The third and fourth columns are headed Generator Input, the third being the apparent input and the fourth the real. The relays are so sensitive that the usual variations in current due to notching are entirely absent. Single-cylinder engines are used in mining to replace man- or animal-power for light work. Products Can an autistic person with difficulty making eye contact survive in the workplace? in., R = radius of the bend in inches, d = diameter of individual wires, and C a constant depending on the number of wires in a strand. Rs = weight of the short length of rope when cage top of the shaft. Then, in whatever position the cages are in the shaft, there is the same weight of rope hanging in each compartment. As an example, required the working-load of a 1-in. The generator field varies with the speed and, by means of a comparatively new type of relay, the acceleration and retardation is entirely automatic, during which time the main armature current is held at a predetermined fixed value. The automatic slip regulator in the secondary of the induction motor has a normal slip of about 3 per cent, and the motor windings and leads about 2 per cent., making a total of 5 per cent. The power rating of the motor in kW or hp. line must be supplied by the flywheel. The crane wheel load, usually referred to as maximum wheel load is the total load in pounds that any single crane wheel will see. "Public domain": Can I sell prints of the James Webb Space Telescope? Other grades of rope require different diameter of drums, as will be seen by studying Tables I. and II. The dotted line shows the input to the line when using the synchronous motor-generator set. There are several methods used in making hoist calculations, but no matter what method is utilized a fair degree of familiarity with hoists and hoisting conditions is necessary before an intelligent analysis and proper selection can be made. R = number of revolutions of engine per min. They are only used where the rope is heavy, and the economy of accurate counter-balancing is clearly indicated, and will offset the extra cost of manufacture. Connect and share knowledge within a single location that is structured and easy to search. Where such calculations are seldom made, it is better to use the longer methods; but where the calculations are made daily, short cuts can often be used to great advantage. Wire rope hoists and components - hoists and end carriages. . This increase is very apparent in figuring out the capacity of the motor, which proves to be 2340 hp. In general, a gearbox is used to match the drive to the load. For example: Assume a 2,000 pound load is to be supported by 2 legs of a sling at a 60 leg angle. When the migration is complete, you will access your Teams at stackoverflowteams.com, and they will no longer appear in the left sidebar on stackoverflow.com. Figure 3 Relationships Between Power, Current, Power Factor and Motor Load Example: Input Power Calculation An existing motor is identified as a 40-hp, 1800 rpm unit with an open drip-proof enclosure. The next size of motor is selected having a capacity of 2000 hp. How can I get a huge Saturn-like ringed moon in the sky? 5. Permitted by general conditions, it should choose the motors with less poles as far as . Then, when we calculate the Acceleration Torque in Torque Calculation we divide the total the total inertia by the gravity from. To calculate load torque, multiply the force (F) by the distance away from the rotational axis, which is the radius of the pulley (r) . The writer has adopted the scheme of using the full time during actual operation, one-third of the time during the rest period for geared motors, and one-half of the rest period for large direct-connected motors. The output of the hoist motor, in horsepower-seconds, is calculated from each part of the cycle and an average efficiency of the hoist motor is assumed at 88 per cent. These values are obtained by adding the variable losses of the hoist motor to the output values in the first column. The output of the hoist is figured at two values, the first being 2100 tons in 7 hr. k represents the bending-stress in pounds, E the modulus of elasticity = 28,500,000, a the aggregate area of the wires in square inches, R the radius of the bend in inches, d the diameter of the individual wires in inches, and C a constant depending on the number of wires in the strand. the bending-stress is found to be 9937 lbs., and from Table I. the maximum safe stress is found to be 22,667 lbs. 1. inches. + .01 X 8000 lbs. The overall efficiency is readily calculated by dividing the actual work done, in horsepower-seconds, by the input to the a.c. motor. 6 are the same as on calculation sheet No. Special drums frequently require a larger number of equations, which of course can be readily taken care of in the hoist calculation form. The friction of the hoist parts, including windage and friction of the cages in the shaft, has been the subject of much controversy. ), this provies all the extra juice and safety factor. for fast coal hoists and 10 to 20 sec. a solid disk. rope on a 6-ft. diameter drum At this time one crank may be on a dead center, so that all the work must be done by the other. The first column in the second row gives the output of the synchronous motor at each point of the cycle; the next three columns give the internal losses of the synchronous motor, and these losses added to the output column give the values in the fifth column, which is the total input to the synchronous motor at each point in the cycle. At the top of the form is place for the name of the customer, filing information, the date, and the characteristics of the power system. Often the inertia of the special drums is high, which in a way defeats the purpose for which the drum is designed. H.P. Where the maximum rope speed exceeds 1800 ft. per min. motor with a pull out of 3 or a 1500-hp. The selection of the accelerating and retarding time depends on the hoisting conditions; this time will vary from 4 to 8 sec. Pneumatic motors are expensive and very loud as compared to hydraulic. and 0.925 kw.-hr. rope on a 10-ft. diameter drum Proof of the continuity axiom in the classical probability model. and 11.8 per cent, for the 2000-hp. Generally these hoists are arranged in pairs, so that one cage ascends while the other descends. The maximum peak load during acceleration is 3050 hp., but this peak is not imposed upon the system suddenly. C = weight of cage and car, This value is assumed to represent the friction throughout the entire cycle. A 1200-hp. motor. They may be divided into the following classes: I. The total no-load losses with motor fields excited are shown under the heading No-load Losses in calculation sheet No. However, air compressors are much more available as compared to hydraulic power . 1 in. The moment of the resistance at starting the load would be the moment of the weight, C + O + R plus the friction, acting with the lever arm D/2as in equation 5. 1 in. In many cases complete equalization is not necessary and considerable saving in flywheel weight and losses can be obtained: by using partial equalization. The second column gives the input to the hoist motor at the various points in the cycle. Oriental Motor commonly provides inertia in oz-in. per ton is obtained. It has been the practice of the Westinghouse engineers to assume that the total friction of a hoist is based on a rope pull of 7 per cent, of the total suspended weight on the drums for single-reduction geared hoists, and 5 and 5 per cent, for direct-connected hoists. Contact Supplier. The usual practice is so to proportion the cylinder that the length of travel is 1 to 2 times the diameter of the piston. per sq. = 2L x N, or. When the load starts from the bottom of the shaft the rope winds on the center of the reel, which is of small diameter, and then, as the load rises, the successive layers increase the diameter of the coil on the reel; thus the leverage of the load increases and the weight decreases. For the medium and larger sizes of a.c. hoists, 2200-volt motors are becoming standard and the most satisfactory control is the magnetic type with air-brake switches in both primary and secondary circuits. The best way to obtain the variable losses is to plot a loss curve for the particular motor, as shown in Fig. Output mechanical power of the motor could be calculated by using the following formula: Pout = * where P out - output power, measured in watts (W); An enquiring mind might think - what if the power is sufficient to lift the load, say the operators try to lift a heavier load, or the load is a bit stuck on the initial lift stage, or wht really happens durng the intial accelration stage as the load moves from a standstill to it's design speed..the fact that a hoist motor is selected with a HUGE overhead of pull out torque - BS466 and 2573 must be used in the procurement spec!! (the change at top and bottom of shaft being made at the same time). These two parameters are the weight to be lifted (150 kilos),and the speed at which they are to be lifted (3 meters per second) The same motor would be recommended, however. Aluminum weighs 165 pounds per cubic foot (based on the numbers from the table above). 2, which also shows the rope speed, kilowatt-hours per ton, and other information in regard to the hoist. The small cylinders make the first cost lower than that of a direct-acting engine; but the gearing for large hoists is a serious objection. whence, y = 12.52 ft. = diameter of large end of drum. In many cases it is necessary to plug the motor to obtain the proper rate of retardation. will range from ten to fourteen poles; from 200 to 600 hp., fourteen to sixteen poles; and from 600 hp. This involves six equations for the plain cylindrical drum. If the value of L chosen for trial gives a ratio of stroke to diameter outside of these limits, another value must be taken for L, and another solution made. 5. With the d.c. field-control system, the d.c. hoist motor receives its power from a d.c. generator, which in turn is driven by an a.c. wound-rotor induction motor of a synchronous motor. 8. In other words, practically all of the high peak load at the moment of starting is absorbed in the rheostat. Making location easier for developers with new data primitives, Stop requiring only one assertion per unit test: Multiple assertions are fine, Mobile app infrastructure being decommissioned, Asynchronous motor joule loss calculation. At this part of the hoist, steam will be admitted for the full stroke and at its maximum throttle-pressure. View All Products, Resource Center Nav Bharat Motor Manufacturing Company. From equations 9 and 10 combined, the mean effective-pressure required in the cylinders to perform the work can be determined. L = length of stroke in feet. Taking L = 4 ft. for a trial and substituting in equation 5 to find the size of cylinders. Where the power system is large and where momentary peak loads are not penalized, a synchronous motor can be used on the motor-generator set. n = number of layers of rope in coil. The engines are direct-acting, the shaft has double compartments, and the cages work in balance; C =5000 lbs., O = 5000 lbs., R = 6100 lbs., P = 60 lbs., L = 4 ft., f = .01, e = 0.7, g = 1, S = 2000 ft. Thus, the geared engine is used mostly for shallow depths and small outputs per day, while the direct-acting engine is used where the output is large. The proportions of the reel can be found as follows : Let D = diameter of the barrel in feet. A real-life Venco Venturo team member can point you in the right direction. Looking at the Lodestar, this hoist can have a variety of different horsepower ratings, depending on the capacities and speeds. Flywheels for such service in America almost exclusively consist of steel plates riveted together making. Where the motor is geared, the moment of inertia of the armature must be multiplied by the square of the gear ratio to refer it to the drum radius. What should I do? Assume, for a trial solution, that rope weighs 2 lbs. (2). These forms have been modified from time to time, in accordance with suggestions by various engineers. From the hoisting cycle, the kilowatt-hours per ton and the overall efficiency of the hoist can be estimated, as shown under the heading Input with Rheostatic Control. Hoisting-engines belong to the slow-speed type of engines. This friction is sometimes assumed on the basis of a certain hoist efficiency of 80 to 85 per cent. If the hoisting conditions do not permit the installation of any but an a.c. motor, it is sometimes possible to meet such a high-speed cycle b applying two motors instead of one. S4 and S5 work system, according to the corresponding YZR power value to calculate. All the info provided in earlier answers covers this. Conical or cylindro-conical drums, in general, cut down the peak load during acceleration and retardation, but in many cases they introduce undesirable elements. Where power-factor correction is not desired, a simple relay could be installed; this would reduce the excitation during light load periods and increase it during heavy loads, thus tending to produce a more nearly constant power factor and saving some power. The temperature rise depends on the motor losses, most of which are dissipated as heat.
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