anyone?

[jonnymc11]

Regarding examples:

20amp socket what type of protection it needs - what is this answer? 16A Mcb

how does a rcbo work -works on overload and short circuit?

how do you improve starting torque on induction motor - more frequency or less poles?

 

[revjames]

A 20A socket, the MCB rating would also depend on the size od the cable feeding the socket. You could protect the circuit with a 20 or even 32A MCB if the cable size was up to it.

RCBO is an MCB and an RCD combined which gives protection against overload/short circuit and also protection against eart faults.

Not really sure about the motor, more poles = slower motor since S = F/poles

HTH

James

 

[sparkytim]

Hi

Not seen a 20 A socket, but a 16 Amp socket can be protected by a 20 A Mcb.

 

[Andy™]

cant think of any 20A sockets in general use.

BSEN 60309 sockets are protected at their max rating, or lower (depending on wiring or expected load), with the expection of 16A, which may be upto 20A

RCBO is an MCB & RCD in one. picks up on overload/fault currents, and earth leakage

 

[cm304eex]

Not one hundred percent sure but if you increase the magnectic field you would have a stronger starting tourque.

 

[jonnymc11]

thanks, what about?

11. A 400v 50Hz has a line current of 50A and 0.8 lagging, The power dissipated will be

A 20KW

B 9.2KW

C 27.712KW

D 16KW

 

[training_spark]

try

p=v X i X cos

i did 400 x 50 x 0.8 and got 16KW not sure if thats correct though

seen ur other threads and i hope u ace the motor questions because i cant stand them lol

one book tells you one thing and on sample questions its always another

 

[cm304eex]

I agree

p=v X i X cos

i the same 400 x 50 x 0.8 and got 16KW

I only had the star and delta formulas in my 203 none of the other lads had many actual motor questions. Would be worth you brushing up on Synchronus and slip calcs.

Good luck

 

[BigMac]

Thinking maybe missing couple of words from question?

root3(1.732) x 400 x 50 x 0.8 = 27712

not sure, only student myself

 

[S60TEM]

Thinking maybe missing couple of words from question?root3(1.732) x 400 x 50 x 0.8 = 27712

not sure, only student myself

correct

 

[training_spark]

ye thats it (some info must be missing)

just remember = √3 x Vl x Il x P.F (the L bit

)

 

[jonnymc11]

thanks lads

 

[steptoe]

if you have a 20A socket and assuming the cable is rated correctly then you require a minimum of 20A MCB to protect it,

if you use a 16A mcb then in effect your 20A socket becomes a 16A socket with 20A style connections.