A packaging machine for producing sealed packages of a pourable product from a web of packaging material; the packaging machine comprises: - a conveying device for advancing the web of packaging material along a web advancement path at least to a tube forming station at which the web of packaging material is formed, in use, into a tube and for advancing the tube along a tube advancement path; - a tube forming and sealing device configured to form the tube at the tube forming station and to longitudinally seal the tube; - a tensioning device arranged upstream of the tube forming station along the web advancement path and configured to control at least the tension of the tube; and - a control unit configured to control operation of the packaging machine; wherein the tensioning device comprises at least - a main drive roller rotatable around a main rotation axis; - a main drive motor configured to actuate rotation of the main drive roller around the main rotation axis; - a package forming unit adapted to at least form and transversally seal the tube during, in use, advancement of the tube along the tube advancement path, characterized in that the packaging forming unit is configured to continuously form the sealed packages, wherein the control unit is configured to control the main drive motor such that an angular speed and/or angular acceleration of the main drive roller is cyclically varied, and an advancement speed of the web repeats according to a defined frequency, such to control the tension of the tube; wherein the control unit is configured to control the main drive motor such that the angular speed and/or angular acceleration of the main drive roller is varied and/or controlled as a function of the operation of the package forming unit. the packaging machine comprises: - a conveying device for advancing the web of packaging material along a web advancement path at least to a tube forming station at which the web of packaging material is formed, in use, into a tube and for advancing the tube along a tube advancement path; - a tube forming and sealing device configured to form the tube at the tube forming station and to longitudinally seal the tube; - a tensioning device arranged upstream of the tube forming station along the web advancement path and configured to control at least the tension of the tube; and - a control unit configured to control operation of the packaging machine; - a conveying device for advancing the web of packaging material along a web advancement path at least to a tube forming station at which the web of packaging material is formed, in use, into a tube and for advancing the tube along a tube advancement path; - a tube forming and sealing device configured to form the tube at the tube forming station and to longitudinally seal the tube; - a tensioning device arranged upstream of the tube forming station along the web advancement path and configured to control at least the tension of the tube; and - a control unit configured to control operation of the packaging machine; wherein the tensioning device comprises at least - a main drive roller rotatable around a main rotation axis; - a main drive motor configured to actuate rotation of the main drive roller around the main rotation axis; - a package forming unit adapted to at least form and transversally seal the tube during, in use, advancement of the tube along the tube advancement path, characterized in that the packaging forming unit is configured to continuously form the sealed packages, wherein the control unit is configured to control the main drive motor such that an angular speed and/or angular acceleration of the main drive roller is cyclically varied, and an advancement speed of the web repeats according to a defined frequency, such to control the tension of the tube; - a main drive roller rotatable around a main rotation axis; - a main drive motor configured to actuate rotation of the main drive roller around the main rotation axis; - a package forming unit adapted to at least form and transversally seal the tube during, in use, advancement of the tube along the tube advancement path, characterized in that the packaging forming unit is configured to continuously form the sealed packages, wherein the control unit is configured to control the main drive motor such that an angular speed and/or angular acceleration of the main drive roller is cyclically varied, and an advancement speed of the web repeats according to a defined frequency, such to control the tension of the tube; wherein the control unit is configured to control the main drive motor such that the angular speed and/or angular acceleration of the main drive roller is varied and/or controlled as a function of the operation of the package forming unit.