July 2009
You are currently browsing the articles from circuitmaniac.com written in the month of July 2009.
Introduction D. C. motors are seldom used in ordinary applications because all electric supply companies furnish alternating current However, for special applications such as in steel mills, mines and electric trains, it is advantageous to convert alternating current into direct current in order to use d.c. motors. The reason is that speed/torque characteristics of d.c. [...]
Written by John on July 31st, 2009 with 2 comments.
Read more articles on DC Motor and Direct Current Machines and Electrical Machines.
Under-compounded generators also operate satisfactorily in parallel but overcompounded generators will not operate satisfactorily unless their series fields are paralleled. This is achieved by connecting two negative brushes together as shown in Fig. (3.16) (i). The conductor used to connect these brushes is generally called equalizer bar. Suppose that an attempt is made to operate [...]
Written by John on July 29th, 2009 with no comments.
Read more articles on Direct Current Machines and Electrical Machines and Parallel Operation of D.C. Generators.
The generators in a power plant are connected in parallel through bus-bars. The bus-bars are heavy thick copper bars and they act as +ve and -ve terminals. The positive terminals of the generators are .connected to the +ve side of bus-bars and negative terminals to the negative side of bus-bars. Fig. (3.15) shows shunt generator [...]
Written by John on July 29th, 2009 with 3 comments.
Read more articles on Direct Current Machines and Electrical Machines and Parallel Operation of D.C. Generators.
In a d.c. power plant, power is usually supplied from several generators of small ratings connected in parallel instead of from one large generator. This is due to the following reasons: (i) Continuity of service If a single large generator is used in the power plant, then in case of its breakdown, the whole plant [...]
Written by John on July 29th, 2009 with no comments.
Read more articles on Direct Current Machines and Electrical Machines and Parallel Operation of D.C. Generators.
In a compound generator, both series and shunt excitation are combined as shown in Fig. (3.13). The shunt winding can be connected either across the armature only (short-shunt connection S) or across armature plus series field (long-shunt connection G). The compound generator can be cumulatively compounded or differentially compounded generator. The latter is rarely used [...]
Written by John on July 27th, 2009 with 2 comments.
Read more articles on D.C. Generator Characteristics and Direct Current Machines and Electrical Machines.
If we are given O.C.C. of a generator at a constant speed N1 then we can easily draw the O.C.C. at any other constant speed N2.Fig (3.11) illustrates the procedure. Here we are given O.C.C. at a constant speed N1.It is desired to find the O.C.C. at constant speed N2 (it is assumed that n1 [...]
Written by John on July 27th, 2009 with no comments.
Read more articles on D.C. Generator Characteristics and Direct Current Machines and Electrical Machines.
Fig (3.9) (i) shows the connections of a shunt wound generator. The armature current Ia splits up into two parts; a small fraction Ish flowing through shunt field winding while the major part IL goes to the external load. (i) O.C.C. The O.C.C. of a shunt generator is similar in shape to that of a series [...]
Written by John on July 27th, 2009 with 5 comments.
Read more articles on D.C. Generator Characteristics and Direct Current Machines and Electrical Machines.
Fig. (3.7) (i) shows the connections of a series wound generator. Since there is only one current (that which flows through the whole machine), the load currentis the same as the exciting current. (i) O.C.C. Curve 1 shows the open circuit characteristic (O.C.C.) of a series generator. It can be obtained experimentally by disconnecting the [...]
Written by John on July 26th, 2009 with 6 comments.
Read more articles on D.C. Generator Characteristics and Electrical Machines.
