Step down transformer questions

[Daley]

So, i've been working on fire alarms for the past few years so not touched a transformer in ages, and i've forgotten almost everything i learnt about them. Just a few questions and sorry in advance if they seem stupid...

Am i right in thinking they only run at full power for a short period and don't run continually at max

how many transformers can be ran off one circuit (32a mcb ring)

I want to run 2 'site lights' a total of no more than 200w and be able to use a drill and multi master intermittently. Can this be done using one transformer and extension leads

Like i say it's been a while and i'm looking it all up again now but just for a quick answer any help would be greatly appreciated

 

[Darkwood]

Firstly - doesn't anyone have college notes to look back on nowadays?... We all can forget areas that don't factor strongly in our day to day work and that is why we we build a folder of notes and while at college.

The operational duty of a TX depends on the type and make and the type of load it serves.

Tx's off a 32amp mcb.... without giving a mcb type and any info as to the Tx been used except the load then its anyones guess, if your using small 110v Tx's then its the inrush that may be an occasional issue if a few are energised together, larger ones may be unsuitable for a standard 32(b) mcb.

As the loading goes '200w' ... its a Tx refer to the most basic of calculations you were taught in your learning years, the same on you should be using to do most everyday load calcs.

I might sound a little picky here but you have asked a question, providing little relevent info to give a good answer and sounding like you haven't even bothered to look into your notes to at least give you a guide where we would then be happy to correct any concerns you have.

 

[Pete999]

Exactly what darkwood said, couldn't explain it any better.

 

[Daley]

I no longer have any works from my learning days due to a house fire, although i was going to read up on it as i said in my question, i've not touched a transformer EVER. I work on installing fire alarms and maintenance i basically pull cables, press buttons and get paid for it. I don't do any calculations. I understand that i haven't given a lot of information in the question as i don't know what information you need from me to give me a reasonable answer. I read up a little last night before bed and learnt about the inrush causing the breaker to trip and what types of transformer are available. I'll do some more research when i'm home... Thanks anyway

 

[Guest111]

1KVA cte should be big enough to run a couple of small site lights not the halogen ones and a drill or multitool at the same time.

 

[Daley]

Cheers Phil, they're 80w LED lights not halogen so that should help. I'll keep reading up...

 

[tazz]

Fire alarm, security alarm, EM Lighting and any other electrical installation requires load calculations.....How can you fit fire alarms without calculating the load being used...?

 

[Daley]

Fire alarm, security alarm, EM Lighting and any other electrical installation requires load calculations.....How can you fit fire alarms without calculating the load being used...?

I don't design fire alarm systems, as i said in my reply i pull cables to make a wage....

 

[Lucien Nunes]

Most yellow portable transformers are rated using the intermittent or 'tool' rating, which is 25% duty cycle, 15 mins off load for every 5 mins on load. Because the heating in the windings is proportional to the square of the load, the continuous rating is approximately half the intermittent rating.

For example, a typical transformer rated 3.3kVA will take 3.3kVA for 25% duty cycle or 1.65kVA continuously. Lights count as continuous load for obvious reasons, so to decide whether a single transformer will be OK with your lights and tools, add double the lighting wattage to the tool wattage and compare with the intermittent rating.

Using one transformer for both lights and tools can cause annoying flickering in the lights as the varying tool load alters the voltage drop in the TX. Commonly seen around site, may not really be noticeable with LEDs.

 

[Daley]

Thanks, i'll check the drill wattage when i'm home! Much appreciated