Control system for a hydraulic elevator, which includes a speed regulator for controlling the speed of displacement of the elevator car

A control system (10) for a hydraulic elevator apparatus (1) which comprises

• an elevator cylinder (5) with a piston (5a) coupled to a car (2),
• a pump (4) having the outlet coupled to the elevator cylinder (5), and
• an electric motor (3) coupled to the pump (4);
• the control system comprising a speed regulator (11) associated with the motor (3) for controlling the speed of displacement of the car (2), and being predisposed for driving the speed regulator (11) in predetermined modes, such that the pump (4) rotates at a speed having a predefined value (W);
• wherein the control system (10) is predisposed for driving the speed regulator (11) such that the motor (3) of the pump (4) is supplied with a voltage having a frequency (f) the value of which corresponds to said predefined speed value (ω), increased by an amount (cft;
• fts, ftD) which is a predetermined function of the working pressure (P1) of the pump (4), such as to balance at least in part the effect of the leakage of hydraulic fluid in the pump (4), and
• wherein said amount or increase (cft;
• fts, ftD) of the supply frequency is determined in accordance with a predefined function of the magnitude of the electric current (I) flowing through the motor (3).