Rockwell Automation 1901 SyncPro - Manual (Page 41)

Programming 5-3
1901-UM020C-EN-P – June 2013
Set Point 4 • Squirrel-Cage Protection Trip Time (at 95% speed)
This time setting determines the maximum length of time the
synchronous motor may run at 95% speed before it is shut down.
The squirrel-cage winding of the synchronous motor is not rated to
run the motor continuously even at no load and therefore must be
shut down if synchronism does not occur. Time should be set to
motor manufacturer's specifications.
Allowable Range: 5 to 80 seconds
Factory Default Setting: 5 s (5 seconds)
Set Point 5 • Squirrel-Cage Protection Trip Time (at 50% speed)
It is possible that a synchronous motor can accelerate only to an
intermediate speed and either not accelerate further or take too
long to accelerate further due to overloading. This would cause
the squirrel-cage windings to overheat if allowed to continue
unchecked. This setting limits the time that the motor can operate
at 50% speed to the safe maximum recommended by the
manufacturer.
Allowable Range: 2 s to Value in Set Point 4
Factory Default Setting: 2 s (2 seconds)
Set Point 6: Squirrel-Cage Protection Trip Time (at stall)
In the event that a synchronous motor fails to accelerate at start up
it will go into a stall condition at zero speed. This can occur if the
motor is overloaded at start. The time entered at this set point
should be the maximum allowable stall time on the Squirrel-Cage
Winding as defined by the motor manufacturer.
NOTE: The squirrel-cage winding of a synchronous motor has a
very limited capability. Generally, the stall time allowed by the
squirrel-cage winding is less than the time that the stator winding
is capable of. It is possible that a motor with a stator capable of a
20 second stall would have a rotor which can only endure a stall
condition of 5 seconds.
Allowable Range: 1 s to Value in Set Point 5
Factory Default Setting: 1 s (1 second)