Brekers,MCCB's,COS

Question 1

• what do protection do breaker provide?

Answer 1

• Over I
• Under V
• Rev I
• fault disc
• Opn+clse safely
• Clear shor circ fault I

Question 2

4 TRIPS on breaker

Answer 2

1. under V
2. Over I
3. Anti shock
4. Pos interlk

Question 3

SACE brekers operated in 2 methods

Answer 3

• MANUAL=Prs handle 11 times,white flag to yellow,press I to close brker,charges open springs,press O to open brker
• AUTO=spring chrge by 220v ac motor,white flag replace by yellow

Question 4

5 Safety devices fitted to MCCB’s

Answer 4

• Thermal mag trip
• manual trip
• electro mag trip
• current limiting fuse
• residual current devices

Question 5

Precaution observed when operating HCOS

Answer 5

• Only in emerg
• Never on load
• remote start inhibited
• Motor stopped

Question 6

properties required for ACOS

Answer 6

• Supply not paralleled thru switch
• N & A supp in tolerance
• When N drop A is on automatically
• delay betwn N & A to allow for V drops
• What N supply restored A drops automatically

N= normal supply A=Alt supply