RAKESH SINGH BADAL IFTM UNIVERSITY

Ptotal Qtotal (5) For example: 1. P1 = -80 Watts P2 = 127 Watts | Ptotal | = 47.0 Watts | Qtotal | = 358.5 VARS | θ | = tan –1                                     | 47 | | 358.5 | = 82.53o       2 . P1 = 127 Watts P2 = -80 Watts | Ptotal | = 47.0 Watts | Qtotal | = 207.0 VARS | θ | = tan –1 | 47 | | 207 | = 77.21o

In a three phase, wye or delta three wire system, under balanced or unbalanced conditions, with any power factor, the two-wattmeter method is a practical and commonly used method of measuring total three phase power. A simplified circuit diagram of the two-wattmeter connections is shown in Fig.1. Figure1 is simplified in the sense that the ammeters, current transformers, selection switch, and polarity switch have been omitted. The polarities of the voltage and current connections to the wattmeters are significant. Note that the line in which the current is not measured, line “c”, is connected to the negative voltage terminal on both wattmeters. Figure 1: Connections for the two-wattmeter method. Notice that this is a three-wire system. The total power delivered to the load is given by Eq.1. P total = P 1 + P 2 (1) As indicated in Fig.1, each wattmeter measures a line current and a line to line voltage. The wattmeter reading indicates the product of line c...

• • Sometimes cells may not be formed because of inadequate part families. • Some cells may have a high volume of production and others very low. This results in poorly balanced cells. • When volume of production changes, number of workers are adjusted and workers are reassigned to various cells. To cope with this type of reassignments, workers must be multi-skilled and cross-trained. • Sometimes, machines are duplicated in different cells. This increases capital investment.

• Reduced material handling and transit time • Reduced setup time • Reduced work-in-process inventory • Better use of human resources • Better scheduling, easier to control and automate

• Every cell contains a group of machines which are dedicated to the production of a family of parts. • One of the problems is to identify a family parts that require the same group of machines. • These layouts are also called as group technology layouts. • • The previous slide shows a facility in which three parts A, B, C flow through the machines. • The next slide provides the information in a matrix form which includes some other parts D, E, F, G, H. • The rows correspond to the parts and columns to the machines. • Just by interchanging rows and columns, eventually a matrix is obtained where the “X” marks are all concentrated near the diagonal. This matrix provides the cells. For example, parts A, D and F require Machines 1, 2, 4, 8 and 10 which forms a cell.

• A process layout is a functional grouping of machines. For example, a group of lathe machines are arranged in one area, drill machines in another area, grinding machines in another area and so on. Different job jumps from one area to another differently. Hence, the flow of jobs is difficult to perceive. This type of layout is suitable for a make-to-order or an assemble- to-order production environment, as in a job shop where customization is high, demand fluctuates, and volume of production low. Since a wide variety of products are produced, general purpose equipments and workers with varied skills are needed. • A product layout arrangement of machines. Every job visits the machines in the same order. This type of layout is suitable for a make-to-stock or an assemble-to-stock production environment, as in a flow shop where products are standard, demand stable, and volume of production high. Since variety is low, special purpose equipments and workers with a limited skil...