Switch Versus Isolator

Measure / calculate the load, add a margin for surges and get an appropriate isolator... err on the high side, it won't do any harm.

I don't suppose there is a big cost difference and a higher rating allows for the addition of further loads.

I'm not sure I see an actual problem... maybe I'm missing something... doubtles one of the electrical rather than electronics guys will enlighten me If have got it wrong.

Dear,

please elaborate about the application OR the Issue.

if this is AT 3 PHASE, 4 WIRE 50 hz a.C., 415 VOLT.:-

When you reffering to 4 pole --- A., that means ,you are reffrering to 3 phase and neutral ? OR are you talking about somr control circuits with 4 pole having -- A rating ?

When we talk about OFF load , it is Off load ON and OFF load OFF.

When we talk about ON Load, it is ON Load ON and ON load Off

In the later case, when you want to make On load On , the switching surge shall be applied as per type of load e.g lighting load may be up to 9 ka ND OR the motive load up to 20 KA or so for load up to 63 A.

The Switch and Isolator functions are similar., i.e switch is for switching ON - OFF and isolator for isolating and again putting the isolated circuit in ON.

nascon

dear

i am not agree with you, when we state 4p 63 A isolator i.e. 3 ph only, so far i have not come across any isolator of that much rating in control circuite, if you pls give me the example, farther more when you said OFF load mean it is Off load ON and OFF load OFF dose you mean load side of isolator is always OFF and primary side of Isolator is ON or OFF respectively, if so that mean load circuite is open and no current is flowing then what is significane of 32 A and 63 A rating?

The difference is the size of isolator - when breaking the line it has TO BE ABLE to break a current of 63A. A 32A breaker would probably burn the contacts.

dear pls clarify where is the question of breaking of current? if the isolator is off load device then load side considered as a open and no current is flowing, so how it break the current? i am really worried bout isolator, can anybody put more light on it?

I think it would be better if you can re-phrase your question. I can't really grasp the meaning. However, the only difference between a 63A 4-pole isolator and a 32A 4-pole isolator is simply that one is 63A rated and the other 32A, ie one is rated higher than the other.

an isolator doesn't have to break current, just provide and maintain electrical isolation. This is achieved by having a certain physical distance between the contacts - which is related to the voltage supply (higher voltage bigger gap). A 32A vs 64A will relate to the current carrying capacity, bigger current = thicker conductors and larger surface area for contacts. A switch has to make and break currents which is where arcing concerns come in. An isolator is an off-load device and should not be used as a switch unless it has been designed to perform both functions.

Thanx HUX, gr8, u have given me the clear idea..any thing more in the relation with switch and Isolators..pls put more light...gud one..

In some applications, a control or a measuring circuit should be fed even when the the load is switched OFF. Consequently, some sort of voltage transformers, current transformers, synchro-tacts, ...etc., may be connected between an isolator and a switch.

As a result, the 63A isolator can feed instruments or measuring circuits more than that of 32A one.

Regards... Samak