guest,
Sure, a run-time meter would be just be one ladder rung: a PLC Input (that is physically wired to your motor starter or "Run" switch, and the Timer that starts and stops when the motor starts and stops. Like this:
|. . . . . . . . . . . . . +-RTO-----------------------+. . . ..|
|. . . . . . . . . . . . . .|. .RETENTIVE TIMER ON . .| . . . .|
|. . . . .I:1/0. . . . . |. Timer. . . . .T4:0. . . . . . .| . . . .|
+-------| |----------|. .Time Base 1.0 sec. . . . .|------+
|. . . . . . . . . . . . . .|. .Preset. . . . .32767. . . . .|. . . . |
|. . . . . . . . . . . . . .|. .Accumulator . . .. 0. . . . | . . . .|
|. . . . . . . . . . . . .. +----------------------------+ . . . .|
|
When I:1/0 is ON, the timer will time until motor stops, and then restart at same time for the next start. If you need more than 32767 seconds total, then use two or more timers, with the second one counting minutes, and so on. On most PLC's there are also built-in clocks that can also be used for timing functions.