Power unit

Abstract

A hydraulic power unit for subsea use is disclosed. The power unit includes a housing containing a fluid, an electric motor mounted in the housing, a distribution pump, a heat exchange unit provided externally to the housing and at least one distribution conduit in fluid communication with the heat exchange unit and the housing.

1 - 15 . (canceled) 
     
     
         16 . A hydraulic power unit for subsea use comprising:
 a housing containing a fluid in a cooling circuit independent of a hydraulic power circuit;   an electric motor mounted in the housing;   a distribution pump driven by the electric motor;   a heat exchange unit provided externally to the housing; and   at least one distribution conduit in fluid communication with the heat exchange unit and the housing, whereby the hydraulic power unit is adapted for the distribution pump to recirculate the fluid around the cooling circuit which comprises the housing, the heat exchange unit and the at least one distribution conduit.   
     
     
         17 . A hydraulic power unit according to  claim 16 , wherein the at least one distribution conduit comprises a nozzle ring. 
     
     
         18 . A hydraulic power unit according to  claim 16 , wherein the electric motor comprises a rotor and a stator, the stator including one or more stator coils and wherein the distribution conduit extends radially around one or more of the motor rotor, the stator and the one or more stator coils. 
     
     
         19 . A hydraulic power unit according to  claim 16 , wherein the distribution conduit is disposed on an inner wall of the housing. 
     
     
         20 . A hydraulic power unit as claimed in  claim 16 , wherein the power unit is a hydraulic power unit with an energy density between 0.45 kW/kg and 0.35 kW/kg. 
     
     
         21 . A hydraulic power unit according to  claim 16  wherein the fluid is any one or more of a coolant and heat transfer fluid. 
     
     
         22 . A hydraulic power unit as claimed in  claim 16  comprising at least two pumps. 
     
     
         23 . A hydraulic power unit as claimed in  claim 22 , each pump is adapted to pump fluid along an associated circuit between the housing and the heat exchange unit. 
     
     
         24 . A hydraulic power unit as claimed in  claim 16 , further comprising a compensator. 
     
     
         25 . A Remotely Operated Underwater Vehicle comprising a hydraulic power unit having a hydraulic power circuit for providing hydraulic power, and further comprising:
 a housing containing a fluid in a cooling circuit independent of a hydraulic power circuit;   an electric motor mounted in the housing;   a distribution pump driven by the electric motor;   a heat exchange unit provided externally to the housing; and   at least one distribution conduit in fluid communication with the heat exchange unit and the housing, whereby the hydraulic power unit is adapted for the distribution pump to recirculate the fluid around the cooling circuit which comprises the housing, the heat exchange unit and the at least one distribution conduit.   
     
     
         26 . A method of cooling a hydraulic power unit for use in a Remotely Operated Underwater Vehicle, the method comprising circulating fluid in a cooling circuit independent of a hydraulic power circuit by the steps of:
 (a) circulating fluid inside a housing;   (b) transferring heat from one or more of a motor rotor, a stator and one or more stator coils of a motor mounted in the housing to the fluid;   (c) circulating the fluid through a heat exchange unit provided externally of the housing to cool the fluid by losing heat to the surrounding water; and   (d) passing the cooled fluid through a distribution conduit inside the housing.   
     
     
         27 . A method according to  claim 26 , wherein steps (a), (c) and (d) are achieved with the use of a pump. 
     
     
         28 . A method according to  claim 26 , wherein the cooled fluid is directed from the distribution conduit onto one or more of the motor rotor, the stator and the stator coils. 
     
     
         29 . A method according to  claim 27 , wherein the cooled fluid is directed from the distribution conduit onto one or more of the motor rotor, the stator and the stator coils. 
     
     
         30 . A method accordingly to  claim 28 , wherein the cooled fluid is sprayed onto one or more of the motor rotor, the stator and the stator coils. 
     
     
         31 . A method accordingly to  claim 29 , wherein the cooled fluid is sprayed onto one or more of the motor rotor, the stator and the stator coils.