Method for starting an electric motor in a hydraulically operated working machine

Abstract

The invention relates to a method for starting at least one asynchronous electric motor of a large hydraulic excavator having a service weight >100 t and having an electrohydraulic drive, in that the particular electric motor is transferred from an idle position to an operating position by using a three-stage motor starting process, wherein the volumetric flow rate of at least one hydraulic pump operatively connected to the electric motor is set to the delivery rate V=0 during all starting stages of the electric motor and the delivery rate V of the hydraulic pump is controlled to a value >0 only after the last starting stage of the electric motor by activating an actuator.

1 . A method for starting at least one asynchronous electric motor of a large hydraulic excavator having a service weight >100 t with an electrohydraulic drive, comprising:
 transferring the respective electric motor from an inoperative position into an operative position by using a three-stage motor starting process;   wherein the volume flow of at least one hydraulic pump which is operatively connected to the electric motor is set to the delivery quantity V=0 during all the starting stages of the electric motor, and the delivery quantity V of the hydraulic pump is not adjusted to a value >0 until after a last starting stage of the electric motor, by activating an actuator element.   
     
     
         2 . The method as claimed in  claim 1 , wherein the respective electric motor is activated using the Korndorfer starting method. 
     
     
         3 . The method as claimed in  claim 1 , wherein, in a first switching stage a control unit closes electrical switching elements, wherein the delivery quantity V of the hydraulic pump remains at the value 0. 
     
     
         4 . The method as claimed in  claim 3 , wherein, in a second switching stage the switching element is opened at the star point of a transformer, wherein the delivery quantity V of the hydraulic pump remains at the value 0. 
     
     
         5 . The method as claimed in  claim 4 , wherein, a third switching stage a pilot control valve remains closed and the delivery quantity V of the hydraulic pump remains at the value 0. 
     
     
         6 . The method as claimed in  claim 1 , wherein after the last starting stage of the electric motor, an actuator element which is embodied as a hand lever is deflected manually, and the delivery quantity V is adjusted between a value >0 and a maximum delivery quantity V max. as a function of the degree of deflection of the hand lever. 
     
     
         7 . The method as claimed in  claim 1 , wherein an axial piston pump is used as the hydraulic pump. 
     
     
         8 . A large hydraulic excavator, comprising:
 at least one asynchronous electric motor configured to be started by a three-stage motor starting process during which a volume of flow of at least one hydraulic pump which is operatively connected to the electric motor is set to the delivery quantity V=0 during all starting stages of the electric motor, and the delivery quantity V of the hydraulic pump is not adjusted to a value >0 until after a last starting stage of the electric motor, by activating an actuator element.   
     
     
         9 . The large hydraulic excavator as claimed in  claim 8  wherein, in a first switching stage a control unit closes electrical switching elements and the delivery quantity V of the hydraulic pump remains at the value 0. 
     
     
         10 . The large hydraulic excavator as claimed in  claim 9 , wherein, in a second switching stage the switching element is opened at the star point of a transformer and the delivery quantity V of the hydraulic pump remains at the value 0. 
     
     
         11 . The large hydraulic excavator as claimed in  claim 10 , wherein, in a third switching stage a pilot control valve remains closed and the delivery quantity V of the hydraulic pump remains at the value 0. 
     
     
         12 . The large hydraulic excavator as claimed in  claim 11 , wherein after the last starting stage of the electric motor, an actuator element which is embodied as a hand lever is deflected manually, and the delivery quantity V is adjusted between a value >0 and a maximum delivery quantity V max. as a function of the degree of deflection of the hand lever. 
     
     
         13 . The large hydraulic excavator as claimed in  claim 8 , wherein an axial piston pump is used as the hydraulic pump.