Vacuum circuit breaker’s solenoid force evaluation

29/12/2009

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

EPE Switchgear -11 & 33KVClosing and Opening Coil

32 mm

Pull gauge

coilStopper block

Plunger

Trip hook/strike

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

14Kgf

232

2)(3.5)29(2(2205)7104 3.5A)F(32mm

2x

2Ai2Noμi)F(x,

Solenoid Force and Stroke RelationshipSolenoid Force and Stroke Relationship!!

μo is the Permeability of free spaceN is the number of coil turnsA is the effective cross sectionali 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

Stroke length (x) mm

Forc

e in

Kgf

Solenoid Force vs Plunger positionSolenoid Force vs Plunger position

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

Summary of solenoid and external forces

Photo Gallery

Force test for EPE 11KV

New Solenoid testing

Force test for EPE 33KVForce test for TAMCO 11KV

Appendix – Solenoid Data Sheet