Stranded Wire and Solid Wire

About Wire

Stranded Wire and Solid Wire:
Stranded wire is helpful, especially in larger wire sizes to enable more flexibility in routing of the wire and offers more durability for applications where vibration and occasional movement of the wire could cause breakage of a stiffer solid wire or rigid stranded conductors.
Generally, for small wires sizes and for static applications with low levels of vibration, a solid wire is chosen as it is easy to bend and route, and low cost. An example of this is Romex type household wire common in #12 and #14 AWG sizes.  As wire and cables increase in size, only stranded formats offer practical levels of flexibility for routing.  As cables get larger still, there is increased need for finer stranding to allow adequate flexibility for ease of routing.  Mechanical Lugs has a wide range of wire lugs UL and CSA approved (UL486) for several popular flexible cable and wire classes – Rigid B and C and compact Flexible Glass G, H, I, DLO and K (MTW Welding Wire Battery Cable).  This enables panel builders to meet correct UL and NEC codes while using conveniently routable wire types.
As an alternative to making large cable flexible the use of paralleling may be employed. In sizes of 1/0 and larger 2 or 3 or more cables may be used side by side provided that the same size, stranding and insulation ratings are used. 
Terminal lugs for paralleling wire allow these multiple wires to be properly tied together at the both ends of the wire run. 

Industrial stranded cable is a coarse stranding class and known as “semi-rigid” stranding types. The idea is that the stranding allows enough flexibility to bend wire without needing to go to full “flex” wire stranding such as those used for mobile power applications like locomotive cable, welding cable and machine tool traveling power cables.
Areas of solid and stranded the same: 
The total cross-section area, AWG or "circular mill" size of a stranded conductor is equivalent to that of a solid conductor for the same designated wire size. This means when looking at a "Number 10 solid wire," compared to a "Number 10 stranded wire" the latter will look slightly larger in diameter but has the exact same total cross-section area of conductive material as the solid Wire. This means the current carrying capacity is the same too. 

Similarly, there will be no less or more voltage drop whether you use stranded or solid wire and the current carrying capacity is the same. The main reason for using stranded is for ease of installation and routing, as it is easier to work with in the larger sizes, because it is more pliable. Also solid wire is not so resistant to vibration and repetitive movement compared to stranded wire so solid wires are for totally static applications.  
Stranded wire is a larger diameter:
Stranded wire has a bigger overall diameter than solid wire due to the air trapped between strands and a correspondingly larger insulation diameter needed to cover the wire. 

To overcome the need for more routing space for flexible wire, some stranded wire types are “compressed” or “compacted” before applying the insulation layer. These wires are cold formed to reduce the diameter of the strands of wire, squeezing out the air spaces while maintaining separation of the strands, which allows much of the flexibility to remain.  This is often used in armored cable sheaths where space is limited and overhead bare cables to reduce wind drag.
Advantages of Solid Wire:
   1. More compact for the same current capacity.
   2. Lower cost (market forces may apply)

Disadvantages of Solid Wire:

   1. Only practical and available in small sizes. 
   2. Flexing or vibration will fatigue the wire and cause it to break.
Advantages of Stranded Wire:
1. More flexible for routing
2. More durable for vibration and infrequent movement.
 Disadvantages of Stranded Wire:
   1. Larger size.    
   2. More costly especially as stranding increases as more processing is required to manufacture it.  
Advantages of Flexible Wire – Large sizes can be routed in tight curves by hand.
Disadvantages of Flexible Wire – Only lugs and connectors used for flexible cables may be used.  Fortunately Mechanical Lugs can stock approved Flexible lugs from 1/0 to 444 kcmil on single, two and three barrel. stocks IHI Flexible wire lugs for flex classes of wire G, H, I, DLO (Diesel Locomotive Wire), K (MTW, Welding wire, battery wire) in Single Port and Double Port 14 – 2/0 and 1/0 – 444 kcmil and Triple Port 6 – 3/0 AWG and Splicer Reducers 6 – 3/0 AWG.
Also Metric MM2, Class 5 wire (similar to Class I and DLO in stranding)