Discuss Inrush current in the Electrical Forum area at ElectriciansForums.net

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Rob

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Motor starting, or is that to brief?
 

plugsandsparks

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do you mean with values ?

Typical example are transformers, big inrush until the field gets established.
Often worse than motors size for size and they dont care whether there is any load.

Manufacturers give the data for inrush curves so you can match it to a breaker
 
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Farmelectrics

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No rob what it is a Madrix main switch with different settings on its a 200a switch set at 1 which is 200a but another dial next to it is set at 5 Madrix tech people said this is for your inrush current I'm awaiting an email of them explaining in better detail
 
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Farmelectrics

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Plug is that what it would trip at 1000a seems very high to me tony explain a bit more
 
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In-rush or start up current is the extra current drawn to start certain items of equipment, such as flourescent lights, discharge lighting, DOL motors, welders, etc.
A setting of 5X the overload current seems rather extreme.
I'd expect 1.5X - 2X, hence type C and D MCBs.
 
K

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Thermal O/L has a time curve the same as you would find on a domestic MCB.
Magnetic O/L is for short circuit protection. It needs to operate fast in the case of a S/C but must allow the magnetising “inrush” current for inductive loads without tripping. It’s a juggling act between sensitivity to short circuit and the let through for inrush.

Several years back I changed a burnt out 300Hp motor, the company policy was that any replacement had to be a high efficiency motor. High efficiency = higher inrush. First test run (direction check) with no belts on the pulleys, all OK. once the belts were put on, Oh dear, the 400A MCCB tripped immediately on instantaneous O/L. We had to fit a new MCCB that could withstand 8X current.
Final settings were I-th .95, I-in 7X. So I-in = 2800A
 

Rob

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As tony has already stated. It sounds like an overload with short circuit protection. Could you upload a photo?
 

plugsandsparks

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Plug is that what it would trip at 1000a seems very high to me tony explain a bit more
AS mentioned, could do with a photo of the switch in question. Or the make and model no. Some of the adjustable ones have setting for various Ix, and sometimes time. They allow you to tune the breaker. Some of these breakers may say they are 140/200 amp breakers, with a setting to tune them down from 200 amp. Some have inrush settings which are " XN " i.e. X the setting of the breaker, i.e. X5 maybe in your case. Some also have a time characteristic to shorten or lengthen the tripping times, a bit like an adjustable MCB.
If you think about it, you have to sometimes energise this breaker on load.
They use terms like In, Ir and Im, i have to look them up everytime.
Hope this helps.
The data should be available online, is most of the time.
I am forever reducing Ir as they always appear to be set at max, i.e. 1
 
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Farmelectrics

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Will try today to upload photo how do I get it on to the forumn from my I phone can't remember
 

plugsandsparks

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Dont have i-phone but on my samsung i connect phone to pc, then i can see all the files from my laptop. I just click image in the reply box and browse to the phone and upload. My laptop uses a programme called Kiers to enable comms to phone.
 

Rob

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You can upload them to the photobucket (its a free app) or similar site, then copy the
 

Rob

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thanks rob how do i move them from my photos to photo bucket

Seems you've already worked it out? Open photobucket app, select choose from library, all straightforward.
 

Rob

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It's setting your magnetic tripping point. As tony has previously stated.
 

plugsandsparks

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Looks like a 200A breaker that can be tuned down to 160A for normal long duration overload. Its currently set at 200A.
The next one is the short term overload (inrush) etc, this is a function of the first one.
i.e. X Ir - it is set to 5 but can go higher to 10, so the max in-rush current is 1000A as its is currently set.

Hope i got that right :)
 

Rob

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I'd of personally said its a thermal, magnetic Mccb. In which case your a little bit off plugsandsparks

Baisically In the thermal-magnetic trip element circuit breaker, a magnetic element (electromagnet) is connected in series with the circuit load, and a bimetallic element is heated by the load current. With normal circuit current, the bimetallic element does not bend, and the magnetic element does not attract the trip barIf the temperature or current increases over a sustained period of time, the bimetallic element will bend, push the trip bar and release the latch. The circuit breaker will trip.

This combines overload protection with short circuit protection.

Sorry re-reading that sounds like I'm trying to teach you to suck eggs. Just much help other people who don't know.

This is all just a presumption, I haven't looked up that type or breaker to confirm.
 

plugsandsparks

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Not disagreeing, you are talking about how it works i was talking about the settings and what they do. Long duration overload, read thermal and inrush settings read short circuit or magnetic
 
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