3RV Molded Case Motor Starter Protectors up to 800 A General data Characteristic curves Example characteristic of a 3RV10 molded case motor starter protector with electronic trip unit for motor protection (TU 4) 1 = Tripping current for protection function L = Tripping current for protection function I = Tripping current for protection function R = Tripping time for protection function R = Tripping current for protection function U = Tripping time for protection function U = Rated operational current of motor = Starting current of motor = Peak value of subtransient starting current = Starting time of motor = Duration of subtransient starting phase = Typical starting characteristic of the motor = Example of a tripping characteristic for a motor starter protector with electronic trip unit t [s] L 5 t 5 3 CLASS 10A CLASS 10 CLASS 20 t 6 6 t a e a p c t a t m p m c t 6 R t p t 5 I NSB0_01951 [A] 6 e a 1 5 3 p TU = trip unit Protection from overload (L trip unit) Protection in the event of phase failure or phase unbalance (U trip unit), can be switched off The L protection function protects the motor from overload and is temperature-compensated according to IEC 60947-4-1 and sensitive to phase failure and phase unbalance.
With the DIP switches on the trip unit the function can be set by hand to between 0.4 and 1 times the rated current. The trip class can also be set here. This function protects the motor when it is important to check in particular for phase failure and phase unbalance. The function responds when the rms value of the current in one or two phases remains 4 seconds long below the limit threshold of 0.4 times the tripping current for the overload. A pre-alarm LED and an alarm LED indicate violation of the pre- alarm threshold (0.9 times the tripping current) and the alarm threshold (1.05 times the tripping current).
Time/current characteristic curves, current limiting characteristic curves and I 2 t curves can be ordered from "Technical Assistance": Either by e-mail to: technical-assistance@siemens.com Or on the Internet: http:/www.siemens.com/automation/service&support Protection from short-circuits (I trip unit) This function protects the motor from short-circuits between two phases. It always responds when a phase exceeds the set trip- ping value (6 to 12 times the rated current). Safe start-up is gu- aranteed. Protection in the event of rotor blockage (R trip unit), can be switched off With this function the motor is protected in the event of rotor blo- ckage during operation.
During motor start-up, this function is blocked for the time defined by the trip class. Thereafter the trip unit trips after 1 to 10 s at 3 to 10 times the tripping current for the overload (each can be set by means of DIP switches). 48 Siemens · 2009 U