1. Vacuum circuit breaker’s solenoid force evaluation 29/12/2009

2. Deliverable 1 Report on the compliance of the brand new trip coil and close coil to specification and their safety factors as derived from the laboratory experiments

3. EPE Switchgear -11 & 33KV Closing and Opening Coil 32 mm Pull gauge coil Stopper block Plunger Trip hook/strike

4. EPE Switchgear -11 KV Solenoid force = ave 14kgf To open VI – Un-serviced = ave 8.4 kgf – After serviced = ave 3.3 kgf – Jammed bearing( Bushes) at linkage= ave 12.97 kgf – Jammed bearing at hook = ave 15.5 kgf – Jammed pin at hook = ave 15.5 kgf Safety factor in force – after service = 14 /3.3 = 4.2 - before service =14/ 8.4 =1.67 - 4.5 cm 0.5cm

5. Solenoid Force and Stroke Relationship ! μ o is the Permeability of free space N is the number of coil turns A is the effective cross sectional i is the max current x is the stroke length of the plunger N.B. Data sheet of the coil attached in appendix ! A. E. Fitzgerald, Electric Machinery: The process, devices and systems of electromechanical energy conversion, McGraw Hill 1971

6. Stroke length (x) mm Force in Kgf Solenoid Force vs Plunger position

7. TAMCO Switchgear Solenoid force = ave 7.75 kgf To open VI – Unserviced = ave 0.58 kgf – After serviced = ave 0.29 kgf – Jammed bearing + pin = ave 0.75 kgf – Safety factor in force – before serviced = 7.75/0.58 =13.3 - after service =7.75/0.29 = 26.7

8. Summary of solenoid and external forces Case Un-serviced Serviced Jammed bearing (bush) links Jammed links bearing, hook bearings & pin External coil Safety factor Breaker Average Force kgf un-serviced serviced EPE 11kV8.43.312.9715.5141.674.2 33KV 12 7.0 waiting >30 14 1.162.0 TAMCO0.580.3 0.9 7.7513.326

9. Photo Gallery Force test for EPE 11KV New Solenoid testing

10. Force test for EPE 33KV Force test for TAMCO 11KV

12. Appendix – Solenoid Data Sheet