type c and b

[Lee321]

so we measure across a transformer with an AC voltage (NOT DC ala your meter!) why do we get a resistance? and that is why we need to use a different characteristic MCB to avoid tripping on this load?ALL electrical loads are resistive to a degree or less, its the nature of the fundamentals of electricity, you still semm to have difficulty grasping the basics.

NOT everything can be found in a book or on google.

no i'm fully aware all loads will have resistance when measured but you seem to have difficulty grasping what happens when a voltage is applied to loads with reactance or no reactance aka inductive or resisitive

 

[steptoe]

so a motor is seen as a load and a tranx is seen as a dead short,

explain that?

and this is not measured with a standard meter, you need to apply an AC voltage to see this happen, as with the resistance across a co-axial cable, apply a DC voltage and it will appear open circuit, apply AC and you see a resistance of 50 or 75 or whatever rating the cable is.

Im just waiting to see how you can explain the different characteristics of the loading for different MCBs in a better sense.

 

[Lee321]

you stated that a trany was a resistive load which it isn't thats all i was pointing out!

you have to be kidding about the motor and the trany right!

 

[SPECIAL LOCATION]

you stated that a trany was a resistive load which it isn't thats all i was pointing out!you have to be kidding about the motor and the trany right!

erm?

go and have a look at ANY electrical component suppliers

say..

Maplin

RS

etc...

look up transformers

along with the spec for each and every one

you will find the load RESISTANCE value for that transformer..

It has to have a suitable load Resistance so as to NOT short out the supply you are putting across it?

Loads are

Resistive AND inductive

or Resistive AND capacitive

or Resistive AND both!

but NOT purely Inductive OR capacitive!

Tis what we were taught...

after how to bake our Hovis!

 

[Lee321]

as i have said all loads will have a resistance.

but types of loads are referred to either resistive or inductive not both unless a eg motor is connected via a resistor etc

yes a motor has resistance but its load charateristic is inductive. full stop

a filament light bulb has resistance but is purely resistive.

.

http://www.allaboutcircuits.com/vol_2/chpt_11/1.html

 

[Apache]

as i have said all loads will have a resistance.but types of loads are referred to either resistive or inductive not both unless a eg motor is connected via a resistor etc

yes a motor has resistance but its load charateristic is inductive. full stop

a filament light bulb has resistance but is purely resistive.

.

http://www.allaboutcircuits.com/vol_2/chpt_11/1.html

The textbooks try to paint a simplified form so that it can be easily understood and we don't have to calculate everything. Science in general is littered with these simplifications put there to make the lives of the people learning it easier.

Now in real life things arn't as clear cut. You're quoting a textbook which in itself isn't wrong but it's not real life.

 

[Mr Sworld]

but types of loads are referred to either resistive or inductive not both unless a eg motor is connected via a resistor etc

You have missed out / forgotten about the third type of load.

Capacitive

 

[Lee321]

The textbooks try to paint a simplified form so that it can be easily understood and we don't have to calculate everything. Science in general is littered with these simplifications put there to make the lives of the people learning it easier.Now in real life things arn't as clear cut. You're quoting a textbook which in itself isn't wrong but it's not real life.

but in real life we know that if we tested the resistance of a motor and did our I=VxR the real current would not be what that equation gave us.

but back to the point of the resistive load and for any of the trainee's reading this if you had a 10a fuse and you had a transformer who's load was 10a and you powered it by a 10a fuse it would blow 9 times out of 10 on turning on. but if you had a filament bulb who's load was 10a the fuse would not blow.

 

[Lee321]

You have missed out / forgotten about the third type of load. Capacitive

agree

 

[SPECIAL LOCATION]

but in real life we know that if we tested the resistance of a motor and did our I=VxR the real current would not be what that equation gave us.

a filament light bulb has resistance but is purely resistive.

so if we tested the resistance of our light bulb we WOULD get the real current..(cuz its purely resistive),

just as if we measured a resistor...

erm...

not quite I don't think....... ?:|

40watt bulb typical say 100 - 110 ohm 230/110 = 2amps!

60watt bulb typical say 60 - 75ohm 230/75 = 3amps!

100watt bulb typical say 40 - 50ohm 230/40 = 5.75amps!

well theres all of my 6amp MCB's power took up then! :_| ?:|

glad thats cleared up...

wondered why I could only put 2 bulbs on me circuit without nuisance trippingBlushing

Bulb is NO more purely resistive than a transformer is purely inductive!

 

[professional]

Since when has a transformer been a (primarily) resistive load? - the output is created by inductance.

Surely the reason why a transformer is usually fed via a Type D mcb is because of the temporarily extra high inrush whilst magnetically saturating a relatively large mass of iron?

 

[Lee321]

Since when has a transformer been a (primarily) resistive load? - the output is created by inductance.Surely the reason why a transformer is usually fed via a Type D mcb is because of the temporarily extra high inrush whilst magnetically saturating a relatively large mass of iron?

thank you

 

[DonkeyDong]

where's the popcorn - this is an interesting show

D. (spent 6 years at college and university doing electrical and electronic engineering)

 

[steptoe]

Since when has a transformer been a (primarily) resistive load? - the output is created by inductance.Surely the reason why a transformer is usually fed via a Type D mcb is because of the temporarily extra high inrush whilst magnetically saturating a relatively large mass of iron?

oh really?

how is the input controlled?

alchemy?

the point of this thread (and forum perhaps) is the OP didnt understand the differing reasons various MCBs were used in what circumstances

I was only trying to explain in simple terms why the different items required different types (B C or D) MCBs, and the reasons.

lostit either still doesnt understand the basic fundamentals,

is still getting his information via google/books/wikipedia or wherever and therefore cant actually form a logical experienced reasoning,

or just really wants to try turn this intelligent forum into the one it replaced.

we are here to help people with their varying questions and degrees of knowledge, not to baffle them with technicallities.

it seems to me quite obvious when a spark asks a question and the answers are uaually appropriate, in this case the OP sounded quite inexperienced to the use of different MCBs, so I tried to explain it in a similar manner.

as and when(if) lostit tends to be able to ask a question with a sounding degree of knowledge then I will answer it likewise, until then I will continue to reply to lostit with the DIY burp his comments require.

his comments and reasoning for varying factors could well be cut and paste, I have yet to see him give a real world reason for anything he posts to in relation to actually trying to make money and ensuring peoples safety.

 

[Lee321]

the thread went off on a tangent because you said something that i believe is incorrect "another topic admittedly" and still do.

the fact that we were and trainees will still be taught in college that resistive and inductive loads are typically a filament bulb or heating element for example and a transformer/choke/motor is a inductive load respectively then mcb's will need to be selected to correctly supply those load types.

you stated that a transformer is a resistive load which it is not referred to as in the industry.

 

[steptoe]

the thread went off on a tangent because you said something that i believe is incorrect "another topic admittedly" and still do.the fact that we were and trainees will still be taught in college that resistive and inductive loads are typically a filament bulb or heating element for example and a transformer/choke/motor is a inductive load respectively then mcb's will need to be selected to correctly supply those load types.

you stated that a transformer is a resistive load which it is not referred to as in the industry.

Im not

you were taught wrong, I never learnt that

well your obviously not in the same industry as me

I dont really care much for your foolish opinions, I have a signature that explains its only mine, but since doing my trade before the 16th even hit in and having actually worked in the industry for quite some time in a few different places I soon learnt that if a transformer wasnt resistive then it would simply blow the protective device straight away as it was merely a dead short,! a piece of wire coiled up between LINE and NEUTRAL!

simple way for you to prove this to yourself is take ten feet of inductance wire and connect it across your incoming tails with NO resistance!

and dont close your eyes when you do it!

let me know tomorrow night how you get on, or should I ring A&E to send you my best wishes?

 

[Lee321]

i'm not sure why your insulting me as i have made no i'll reference to you personally. if i state what i have been taught why am i foolish !!

i could think like wise of your teaching!

 

[Lee321]

A TRANSFORMER HAS RESISTANCE but its load type is not resistive

 

[steptoe]

i'm not sure why your insulting me as i have made no i'll reference to you personally. if i state what i have been taught why am i foolish !!i could think like wise of your teaching!

its not intended as a personal insult, more a way for you to prove to yourself how resistance works in the real world,

do you really do everything the way they told you in college?

thought not, so what makes them right about everything else?

this is the real world, not the theoretical world that exsists in college or in books.

it was a simple easy explaination to an easy question, look at the OP again and tell me my answer was wrong.

 

[SPECIAL LOCATION]

Since when has a transformer been a (primarily) resistive load? - the output is created by inductance.Surely the reason why a transformer is usually fed via a Type D mcb is because of the temporarily extra high inrush whilst magnetically saturating a relatively large mass of iron?

I assume here we are ignoring all of the hundreds of thousands of everyday applications of transformers that are quite happy from a type B mcb??? ?:| :|