Siemens GMI Series Instruction

lnterru rator DescriRefer to Figure 28c. An electrolytic capacitor resides acrossthe tripping supply voltage connected through a half waverectifier and resistor. The rectifier allows the capacitor toassume a charge approximating the peak voltage of the ACtripping supply voltage. The series resistor limits the magni-tude of charge current flowing into the capacitor.The charged capacitor is then connected across the breakertrip coil circuit through an external contact which closes upontrip command.The capacitor size and charge current magnitude are tuned tothe inductance and resistance of the tripping solenoid, an RLCseries circuit, to produce a discharge current through thesolenoid which emulates the magnitude of current and currentduration which the solenoid would experience if operated froma DC tripping supply voltage.Undervoltage Release (Optional}The undervoltage release is used for continuous monitoring ofthe tripping supply voltage. If the trip supply voltage fallssignificantly, the undervoltage release will provide for auto-matic tripping of the breaker.Description of Operation- The undervoltage release consistsof a spring stored energy mechanism, a latching device and anelectromagnet. These elements are accommodated in asingle assembly as shown in Figure 29.The stored energy spring ( 1), spring charging arm (2) and latchface are arranged in a cylindrical assembly concentric with thetrip latch shaft (3). The cylindrical assembly is retained by thesupport bracket (4), yet remains free to rotate. The cylindricalassembly is supported by the trip latch shaft which rotatesfreely on the trip shaft supported by needle bearings.The stored energy torsion spring ( 1) has one tail bearing on alug fixed to the cylindrical assembly, and an opposite tail fixed''lon a lug of the support bracket. the torsional tension ofthe spring will cause the cylindrical assembly (5) to be forciblyrotated relative to the support bracket.The cylindrical assembly is notched at the end nearest themechanism side sheet with the notch engaging a spring pin (6)driven into the trip latch shaft. The notch has sufficient arcwidth to permit the trip latch shaft to rotate normally in responseto the breaker receiving a trip command.The breaker jackshaft (7) is fitted with an arm and track roller(8) which bears on the charging arm (2) of the cylindricalassembly. Whenever the breaker is opened, the arm and rollercause the charging arm to be rotated charging or winding upthe stored energy torsion spring.A spring loaded latch arm (9) rises to engage the latch facewhich is an integral feature of the cylindrical assembly. Thelatch arm (9) is held in this position by the vertical lever (10)which is pulled to the supporting position by the electromag-net. The vertical lever is pivoted (11) by the electromagnet (12)against the force developed by a extension spring (13) whichconstantly attempts to pull the vertical lever ( 10) into a positionwhich releases the stored energy torsion spring.The latch arm supported by the vertical lever retained inposition by the electromagnet will retain the stored energystate until the electromagnet senses a loss of trip supplyvoltage. When the supply voltage falls to a level 30 to 60percent of nominal, the electromagnet releases the verticallever, the latch arm descends and the cylindrical assemblyrotates displacing the trip shaft. Latching is established at 85%nominal voltage.InterlocksThere are two interlocks which prevent certain unsafe operat-ing conditions. They are the rating interlock and the trip-freeinterlock.6 ROLL PIN IN LATCH SHAFT ASSY3 LATCH SHAFT ASSY7JACKSHAFT-lf-!;==fl--'--. J CENTER LINE-!R=--it=;;;""'1HLJ r--{Figure 29: Undervoltage Trip Option2LATCH SHAFT ASSY9101219