Start-Transcript is a PowerShell commandlet which causes PowerShell to log all output to a file. It uses the current window size (i.e. column count) to calculate line breaks in the generated file.
The PowerShell window is 120 characters wide by default. Thus a log file generated by Start-Transcript will reflect this 120 character limit.
You can even change the PowerShell window size using the Get-Host commandlet:
$h = get-host
$win = $h.ui.rawui.windowsize
$win.width = 120 # change to preferred width
However, if PowerShell is invoked from a batch file being executed in cmd, the PowerShell window is only 80 characters wide, since the cmd window is (typically) 80 characters. Calling set_WindowSize will have no effect (apart from an error message), because the PowerShell window cannot have a greater size than the parent window.
To adjust the cmd window width before executing a PowerShell script, use the good old MODE command from DOS era:
mode con cols=120
PowerShell will now inherit the desired window width, and line breaks in the log occur where you expect them from working in the PowerShell window.