Auxiliary refrigeration system and operating method

Abstract

Auxiliary refrigeration system used to refrigerate a wind turbine's gearbox ( 10 ) when the main refrigeration system ( 20 ) is inoperative due to low outside temperatures. The auxiliary equipment ( 30 ) is installed inside the nacelle and comprises a pressure limiting valve ( 31 ), an exchanger and a motor fan (M), all of them connected to a control cabinet that activates or deactivates the auxiliary refrigeration equipment ( 30 ) based on the exterior temperature Text, the temperature of the refrigerant at the outlet of the main circuit Tsc, and the gearbox temperature Tm.

1 . Auxiliary refrigeration system ( 30 ) of the type used to refrigerate a wind turbine's gearbox ( 10 ) when the main refrigeration equipment ( 20 ) is inoperative, wherein said auxiliary system is installed inside the nacelle with no contact with the outside and incorporates a pressure limiting valve ( 31 ) and is connected between the established outward ( 12 ) and return ( 13 ) paths from the gearbox ( 10 ) sump and regulated by a refrigerant impelling electrical pump ( 11 ). 
     
     
         2 . Auxiliary refrigeration system according to  claim 1 , which comprises an exchanger and a motor fan (M), all of them connected to a control cabinet that activates or deactivates the non-return pressure limiting valve ( 31 ). 
     
     
         3 . Operating method for a refrigeration system for a gear box comprising a conventional refrigerating circuit through which refrigerant flows and the activation-deactivation of the electrical pump ( 11 ) that impels such refrigerant, and an auxiliary exchanger circuit comprising a valve and an auxiliary exchanger, which method comprises:
 if the pressure in said valve ( 31 ) of the auxiliary refrigeration circuit exceeds the allowable charge losses, the auxiliary exchanger circuit opens, and once a maximum temperature is exceeded in the gearbox, the auxiliary exchanger ( 30 ) is switched on ( 30 );   Based on the outside temperature, the logic regulating the auxiliary circuit or the main circuit is activated;   if the measurements of the refrigerant temperature at the outlet of the main circuit, are equal to or less than a given temperature, and the temperature at the outlet of the gearbox sump exceeds a given temperature setpoint, the electrical pump ( 11 ) and the auxiliary exchanger ( 30 ) are switched on.   
     
     
         4 . Operating method for an auxiliary refrigeration system according to  claim 3 , wherein the pressure valve ( 11 ) starts operating upon reaching 6 bar. 
     
     
         5 . Operating method for an auxiliary refrigeration system according to  claim 3 , wherein the electrical pump ( 11 ) and the auxiliary exchanger ( 30 ) are switched on if:
 the outside temperature is below T BT  and   the temperature (pressure or flow) at the outlet of the main circuit Tsc, is equal to or less than the temperature of the oil whose viscosity is causing charge losses such that it cannot be impelled by the installed pump (or equal to zero in the case of pressure and flow) and   the gearbox temperature Tm, is greater than a safety value in order to prevent the oil from reaching a critical temperature.