What is the concept of "Fixed Working Capital"?

The fixed working capital is that portion of capital that are necessary to be mantain in business without this fixed capital a business can not compete in industry . 

For example to invest15 % in inventory becuase if you not investing in inventory  how u will operate smoothly.

Fixed capital does not mean fixed in location. Capital like plant, tractors, and factories are called fixed because money spent upon these durable goods, remains fixed or unrealised for a long period in contrast with the money spent on purchasing raw materials which is recovered as soon as goods made with them are sold.

 Fixed working capital gerally consists of stock of finished goods for a trdingt firm and stock of raw materials for a maunufacturing concern along with fuel and electricity bills that are needed to make the co work in the short run.

For a power plant it could be stock of coal, and finance to purchase the stock of coal for the fortnight.