Hydraulic system for construction machine including emergency control unit for electric hydraulic pump

A hydraulic system of a construction machine comprising an emergency control unit for an electric hydraulic pump, the hydraulic system comprising:

• first and second electric hydraulic pumps, which are pressure control type variable capacity pumps;
• a plurality of main control valves configured to selectively control a flow of working oil discharged from the first and second electric hydraulic pumps;
• a plurality of working machines and first and second travel pumps driven through the working oil supplied from each corresponding main control valve among the plurality of main control valves;
• a straight travel control valve configured to set a supply path of the working oil supplied to the first and second travel pumps;
• an electronic control unit configured to control the quantity of outlet flow of the working oil of the first and second electric hydraulic pumps by outputting pressure control electric signals for the first and second electric hydraulic pumps based on flow signals of the first and second electric hydraulic pumps and an operation signal of a joystick within an operation seat;
• and
• an emergency control unit configured to output the predetermined pressure control electric signals for the first and second electric hydraulic pumps when the electronic control unit fails to operate,
• wherein the emergency control unit is configured to selectively control the quantity of outlet flow of the first and second electric hydraulic pumps according to the amount of load of the working machines.