Hello friends, in this article we will know that three strings DC What is a three wire DC system? What is the advantage of three wire DC system? And learn about many facts related to it.
Three Wire DC System | Three wire DC system
direct for general power purposes stream Its major disadvantage lies in the fact that its voltage cannot be easily changed, except through the use of rotating machinery, which is very costly in most cases. 3-wire DC The problem can be solved to a limited extent by using
System which provides two voltages viz. V volts between any external and neutral and 2V volts between the externals. Motor loads requiring higher voltage are connected between the exteriors while lighting and heating loads requiring lower voltages are connected between either exterior and neutral.
Due to the availability of two voltages, 3-wire system is preferred over 2-wire system for dc distribution.
Figure 28.27 shows the general principles of a 3-wire dc. Arrangement . It consists of two outer and a middle or neutral wire that is placed at the end of the generator. The neutral wire’s potential is half between that of the external one.
Thus, if P.D. There is 440 V between the outers, then the positive is at 220 V from the outer neutral and the negative is 220 V below the outer neutral. The current in the neutral wire will depend on the load applied on both sides.
- If the loads applied on both sides of the neutral are equal (i.e. balanced) as shown in Fig. 28.27, then the current in the neutral wire will be zero. Under these conditions, the potential of the neutral will be exactly half the potential difference between the outside.
- If the load on the positive external (I₁) is greater than the negative external (I₂), then out of the equilibrium current I, I will flow from the load end to the supply end in the neutral wire as shown in fig. Fig. 28.28 (i). Under this condition, the neutral wire’s potential will no longer be midway between the external’s potential.
- If the load on the negative external is greater than the positive external (I₁), then out of equilibrium (I₂–I₁) current will flow from the supply end to the load end in the neutral as shown in fig. 28.28 (ii). Again, the neutral potential will not remain halfway between the external potential.
- Since the neutral only carries the out of balance current which is generally small, the area of the neutral’s x-section is taken to be half that of any external current.
It may be noted that it is desirable that the value of voltage between any external and neutral should be the same. This is achieved by distributing the load equally on both sides of the neutral.