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NewboY
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3ph Heater Elements

07/31/2014 6:46 AM

What would be the effect on heating if I applied 575V on 400V 3 phase elements. Is it only harmfull for the insulation in the long run?
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Crabtree
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#1

Re: 3ph Heater elements

07/31/2014 6:52 AM

Well, the current would go up by (575/400)^2, roughly. What is the manufacturer's spec? Can they handle it without melting? What about the wiring and the fuseholders? Have you meggered them to a higher voltage for insulation testing? Can it handle the increased current or will a fuse go first? Do you have a qualified Electrician on site or is everything DIY and hope for the best? Only you can see what you're doing, Mildred!

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NewboY
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#2

Re: 3ph Heater elements

07/31/2014 6:58 AM

Maybe only by the factor (575/400).
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Crabtree
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#3
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Re: 3ph Heater elements

07/31/2014 7:03 AM

My mistake. The power would go up by the square of the increase. Better be ready for it, otherwise you won't bee too popular with your fire insurance company.

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TonyS
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#4

Re: 3ph Heater Elements

07/31/2014 9:40 AM

I've got to ask, why do you want to do this?

To me this sounds like a homework question.

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RAMConsult
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#5

Re: 3ph Heater Elements

07/31/2014 10:00 AM

It won't be harmful to the insulation in the long run because in the short run the element will burn out.

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Crabtree
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#6
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Re: 3ph Heater Elements

07/31/2014 10:32 AM

Either that or the fuses!

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Kilowatt0
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#7
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Re: 3ph Heater Elements

07/31/2014 12:29 PM

Not to worry, I'm sure the element will burn out to protect the fuses!

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redfred
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#8

Re: 3ph Heater Elements

07/31/2014 12:42 PM

Depends on a whole lot of things you apparently do not know. At the very least, whatever this heater is heating will get hot initially faster than it did before. How hot it gets will depend on the unknown information of the thermodynamics. How long this faster heating rate will happen depends on the thermodynamics and the electrical elements breakdown voltages.

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Fredski
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#9

Re: 3ph Heater Elements

07/31/2014 5:24 PM

why are you turning it into a fuse?
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TonyS
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#10

Re: 3ph Heater Elements

07/31/2014 5:40 PM

If the heat dissipation is sufficient the elements won't burn out. I found out the hard way when a mill gearbox failed.
The oil circulation heaters had been wired in ∆ instead of Y, the result was carbonized oil ruining the gear box. The heaters tested perfectly afterwards as they had been in a constant flow of oil.

The thermostat did kick in and out fairly rapidly but nothing that seemed untoward at the time.

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RAMConsult
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#11
In reply to #10

Re: 3ph Heater Elements

07/31/2014 8:09 PM

The thermostat kicking "...in and out fairly rapidly..." is what saved the elements, in combination with the oil "coolant" it limited the temperature of the element. Without the thermostat the oil would have carbonized on the element and would have reduced the heat transfer as the carbon built up and acted as an insulator until the element failed. In effect the thermostat acted like a "chopper" and reduced the duty cycle from 100% to the ratio of the off-time to the on-time.

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TonyS
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#12
In reply to #11

Re: 3ph Heater Elements

08/01/2014 7:39 AM

The oil carbonised anyway, it must have flaked off the elements as they heated and cooled. Once in the bearings that was the end.
A brand new coal plant, the mill gearbox lasted just two months.

A damned expensive way to find out the heaters were connected incorrectly.

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sohail0110
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#13

Re: 3ph Heater Elements

08/01/2014 8:34 AM

a small spark will accrue after some seconds of operation and thats all ,but i assure to the safety of your insulation (because it will never last long) .

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Anonymous Poster #1
#14

Re: 3ph Heater Elements

08/05/2014 1:29 AM

you are going to burn your place down to the ground
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Anonymous Poster (1); Crabtree (3); Fredski (1); Kilowatt0 (1); NewboY (1); RAMConsult (2); redfred (1); sohail0110 (1); TonyS (3)

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