How to choose the right 3 pole isolator

[Richiespark100]

Hi guys,

i need abit of help here I have a 3phase, 440v, 50hz, 1.7kw squirrel cage motor. I need to know how I can calculate and choose the right boxed rotary isolator switch. From my calculations I would do PV which equals 3.86. Now this is where I come stuck because it's 3phase do I now times the 3.86 by 3 and say that is my full load current? At the moment I'm thinking of getting a 25 amp isolator switch would this be ok? Please help us out.

Ok guys il try reply to a few of your queries. First of all the type of isolator I want is this: http://www.meteorelectrical.com/25-amp-3-pole-polycarbonate-boxed-isolator-switch.html

also yes it is a 1.7 kW motor 3ph motor it's only a small motor serving as a toilet extract fan working with another 1.7 kW motor as duty/standby. I'm looking to see what is the right isolator to choose. Please give us hand guys


Regards

Richie

 

[Knobhead]

I've got a slightly older book on the subject, I believe it was printed in 1939 and makes reference to the 10th edition regulations as being the latest edition. I can highly recommend it, it's called 'Stubbs electrical encyclopedia'

I've got three volumes of Stubbs 2, 3 & 4. Still usefull for theory.

 

[davesparks]

Ive got all four volumes of what I believe is the last edition to be printed, minus the last two pages of volume 3 (pages 1055 and 1066)

Mine all have blue covers with a picture if a pylon on the spine, I think the earlier editions had different pictures on the spine of each volume.

I think many people could benefit from reading the entry for 'electrician' amongst other things.

 

[Knobhead]

The bottom of page 1056 says "End of volume three"

You've only two pages missing.

 

[davesparks]

I know, I meant 1056 not 1066 in that post!

 

[Knobhead]

I guessed you did, just after I clicked post.

So you're missing the kinky bits..........

 

[davesparks]

I always miss the kinky bits

 

[Knobhead]

The last entry is for rubber gloves.

 

[davesparks]

Are they vulcanised and wrapped with cotton tape like every other mention of rubber in them books?

 

[LeeH]

Here's the proof of the motor plate guys

That's 1.27 at 60Hz. It will be a standard 1.1KW at 50Hz.