Instructions: Select the number of phases from the drop-down list Enter the motor rated voltage in volts (V) Enter the motor power rating and select the appropriate unit (HP or kW) Enter the power factor and efficiency of the motor The hoist and trolley arrangement: This is another important component in the overhead crane. Resource Center, Support The shaft horsepower-seconds for the actual work done in hoisting the coal is obtained by mutiplying the load hoisted by the distance and dividing by 550. Other grades of rope require different diameter of drums, as will be seen by studying Tables I. and II. The speed of your bot is the wheel circumference2rtimes the rpm, with unit conversions where needed. If the average speed of hoisting is kept at about 2/3 of this maximum, the average speed will not exceed 600 ft. per min. 5, which graphically shows the comparison. Then the motor rpm will be: 43.4*34.5 =1497.3 [1500 rpm rated]. Experiments have shown that, in starting with six inches of slack rope, the stress in the rope is about double that due to picking up the load gently. They must be started to a fair speed, in order that the fly-wheel may develop sufficient momentum to carry the crank over the center, before the friction is thrown in to pick up the load. Mr. William Hewitt has shown that, when the diameter of the sheave or drum is 44.5 times the diameter of a 19-wire cast-steel rope, the bending-stresses are 2/3 and the remaining useful strength is 1/3 of the maximum safe load that the rope will carry. The bisectrix of the fleet-angle should strike the middle of the drum. n = effeciency of hoist. The magnetic type of control readily lends itself to the application of safety devices, such as automatic acceleration, overload trip, low-voltage trip, brake magnets, interlocking reverse switches, geared and hatchway limit switches, etc. If these losses were proportional to the load upon the motor, it would be a simple matter to determine the average load and select a motor of the same capacity. In order to better illustrate the value of the method, examples are given showing the determination of the electrical equipment of an alternating- current hoist, a direct-current hoist with flywheel motor-generator set, and a direct-current hoist with a synchronous motor-generator set. Find, compare and create a bid for hoists and service cranes using this complete collection of tools. Generally these hoists are arranged in pairs, so that one cage ascends while the other descends. Click Here. With double-drum hoisters, where the descending cage and car counterbalance the ascending ones, the general equation 5 still applies, but the value of W and F are changed. Under such conditions the best solution seems to be the application of a d.c. hoist motor receiving power from either a flywheel or synchronous motor-generator set. Here's how you would calculate the load weight of a block of aluminum that is 6 feet long, 3 feet wide, and 4 feet tall: Volume = Length x Width x Height. The total input, in horsepower-seconds, can be readily converted into kilowatt- hours from which the value 1.275 kw.-hr. The forms are so arranged that a single sheet 8 by 11 in. motor will have ample capacity. at throttle, corresponds to a cut-off of about . 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 high-speed motor, on the other hand, requires a high gear ratio and the equivalent inertia at the drum rim is very high. It is seldom that most of the information required under the heading General Data is obtained from the customer; the first seven items are usually given and the engineer recommends or estimates the other eleven. 7, which indicates that the total power to be absorbed is 7071 hp.-sec. The electrician makes the following measurements: Measured Values: V ab = 467V I a = 36 amps . 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. Searching for new units, parts or technical knowledge? 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. Where very deep mines are involved, the weight of the suspended cable will often more than balance the load, causing the power to become negative. https://www.youtube.com/watch?v=l7-ju2b4h2U. There must be a division left between the ropes on a conical drum in order to furnish positive grooves for the rope, so that the large coils cannot slip down over the smaller ones; hence the drum must be longer than those of the cylindrical design, even when the mean diameter of the conical drum is the same as the diameter of a cylindrical one. Height of the crane:4400mm Max. The retarding time is frequently made less than the accelerating time, as the friction of the hoist assists during retardation. 60 - number of seconds in a minute. From the total horsepower-seconds, the input is found to be 2.31 kw.-hr. = 13,080 lbs., and ultimate strength of rope should be 7 X 13,080 =91,560 lbs., which would require a 1-inch- diameter flexible cast-steel rope, having an ultimate strength of 100,000 lbs., and weighing 2.45 lbs. These tabulated are: The conditions in all of the above were the same as used in former examples, except that the diameters of drums are all taken as 9.76 ft., which is the mean diameter of the conical drums. With a single shaft, the time to raise one load is the time to change or load cars at the bottom, hoist loads, change cars or dump at the top, and lower the empty cars; while, in a double shaft, two cars could be handled while the above programme was being carried out in a single shaft, as the second load would be raised while the first empty was going back down, and changing of cars at the top and bottom would be going on simultaneously. inch. for the average power delivered to the generator. or 2 TM. The present problem will be worked out upon the basis of complete equalization with a slip, of 10 per cent. up, sixteen to twenty poles. The speed of hoisting, in feet per min., divided by the circumference in feet, will give the number of revolutions of the drum per minute. (9979 kg.) 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. (2). The total no-load losses with motor fields excited are shown under the heading No-load Losses in calculation sheet No. 4, is nearly two times that of the 1500-hp. t = (4 x H x N x T/ V x 60) hours (h) = (4 x 3 x 16 x 8/ 8 x 60) = 3.2 h which is < 4 h. Number of starts per hour when two extra start-ups are estimated for each normal start. f = coefficient of friction. instead of 610. motor may go as low as 100 hp. The no-load loss of the set is 74 hp., or somewhat larger than with the flywheel set; as the synchronous motor is much larger than the induction motor, its losses, including excitation, more than make up for the flywheel loss with the induction motor set. which, with 60 lbs. This friction is sometimes assumed on the basis of a certain hoist efficiency of 80 to 85 per cent. 4, y + D/2 x n = l, and (y D)12/2t = n. Substituting the latter value of n in the first equation gives. motor would have sufficient capacity as far as heating is concerned, but would probably not have a sufficiently high pull out. and will be surrounded by a sheet metal case to cut down the windage and prevent accidental contact by persons in the vicinity. Lifting Height: Main Hoist 20.5mAux. The final value obtained is 610 hp., showing that a 600-hp. 5, Fig. The loss in the slip regulator varies throughout the cycle, the average is estimated to be approximately 7 per cent., or about 35 hp. They also take care of overwind in either direction. The calculations for an a.c. motor are given in hoist calculation sheet No. They seldom have governing-devices, their speed being determined by the hoisting-engineer by means of the throttle, the link-motion and the brake. After entering the required data, click on the "Calculate" button to . Cable Size Calculation of 125 Kw LT Motor Motor KW = 125 Pf = 0.8, Efficiency = 94% System Voltage, V1 Cable length = 200 m Load Current = P / (1.732 x V x Pf x Eff) > (P = 3 x Vx I Cos = for three phase circuits) = 125000 / (1.732 x 415 x 0.8 x 0.94) ~ 230 A This is the full load current cable needs to cater in Ideal condition. If they are directly connected, the ratio of gearing, g, equals 1. https://www.youtube.com/watch?v=l7-ju2b4h2U, When the weight of the load, size of the drum, and steam pressure are given to determine the size of the cylinders, there are two unknown quantities in the equation, viz. In a large majority of cases, the available electric power is alternating current, three phase, 60 cycles. and the pull out required will have to be at least 2, based on the 50 rating. There is, however, considerable 25-cycle power in use; and in a few instances constant voltage direct current is the only power available for a small or an occasional medium-size hoist. These recommendations are often influenced by the available machines that have been built and may be the cause of a variation in the capacities recommended by different manufacturers. The size of the rope fixes the minimum diameter of the. We use cookies to ensure that we give you the best experience on our website. They may be divided into the following classes: I. By this means the maximum load on the induction motor is fixed at a predetermined value. As the loaded cage ascends and the empty cage descends, the amount of unbalanced cable changes rapidly. Some of the hoist calculation methods are long and complicated. stroke. Having settled the size of the useful load to be hoisted, the size of the rope must be determined. Most gearboxes are used as reduction gearbox (i.e., to reduce the rotational speed). O = weight of ore, and Why can we add/substract/cross out chemical equations for Hess law? As the current in the hoist motor is proportional to the torque, this fine also represents the current from which the heating can be calculated. should be close to the actual power loss. This paper outlines the method of calculating the necessary size of motor needed to drive a lift or an escalator. Direct Acting:Single Cylindrical Drum. 1, shows the complete calculations for hoisting 2100 tons in 7 hr. The rapid increase in reliability, the low cost of operation, the ready application of safety devices, and the growing availability of central-station power have made the question of installing a hoist of the electric type no longer debatable. It will be readily noted that a considerable portion of the motor capacity is due to acceleration and retardation. Pulling out standards to calculate a simple gravitational potential energy equation seems a bit silly, but still a good answer. 1. = 100 lbs., D = 7 ft., P = 60 lbs., g = 1, f = .01, e = 0.7, L for trial = 4 ft., to find diameter of cylinder. y= diameter of coil of rope, when cage is at the top, in ft, Let us assume the same set of specifications, except that the output per day is 3000 tons. ), this provies all the extra juice and safety factor. 1) According to the power supply . The load cycles for both alternating-current motors are plotted in Fig. All loads on the generator are directly transmitted and must be supplied by the synchronous motor, while with the flywheel this was not directly the case, since the flywheel takes care of all peak loads and sudden fluctuations. Crane Weight The maximum weight of the crane to be used 50,000kgs (worst case scenario) 2. Cantilever cranes (pillar, jib and wall) ; the kilowatt-hours per ton is 1. In other words, the hoist motor delivers a high torque at the start with a low expenditure of power, for there are no rheostatic losses. As before stated, a fair knowledge of hoist and hoisting conditions is necessary to use these forms intelligently, as well as a knowledge of the various pieces of electrical apparatus necessary to make up a complete hoisting equipment. The motor is 12-years old and has not been rewound. If you have multiple cranes or hoists on a common conductor system: Run the 610.14 (E) (2) calculations for each crane or hoist. In the foregoing case, the average load, upon the motor is 450 hp. There's lots of other stuff such as temp requirements/ frequency of switching cycles, number of lifting cycles to be considered. H.P. = 2L x N, or. On two speed hoists, the slow speed is generally one-fourth the hoist main speed. is based on the formula k = Ea/2.06 R/d + C in which. stroke, and two drums, each 7 ft. 6 in. 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!! To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Single-cylinder engines are used in mining to replace man- or animal-power for light work. A 1200-hp. These losses consist of the copper, iron, friction, and windage. According to table, hoist group FEM 3m. If the ratio is decided upon first, then the area can be expressed in terms of the stroke, and there is only one unknown quantity in the equation. wound for 2200 volts, three phase, 60 cycles, twenty pole. The development of this motor, however, would probably cost several thousands of dollars, which would make it non-competitive.
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