Scr recommendation (or Triac recommendation)

I need a recommendation for a scr to run 18 heat lamps at 175w each. I’ve tried the “10000w” Chinese ones but they run hot.

What V and AC or DC are they switching ?

You using a heatsink, maybe show picture of SCR prototype....

You switching 18 x 175W = ~ 3KW with one part ? Or one SCR / lamp ?


Regards, Dana.

I’m using an off the shelf Chinese scr but it will only safely run 8 lamps. I would hopefully like a recommendation for one that will do 16 lamps and won’t overheat, preferably one without a fan due to the corrosive atmosphere in farm buildings.
UK 230v ac only

Thank you

Martziniuk said:

I’m using an off the shelf Chinese scr but it will only safely run 8 lamps.

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"Safely" means what? A readable photo of the type plate would be helpful.

Generally, triacs and SCR have a characteristic forward voltage that isn't much reduced by using higher current devices. Respective power loss and heat dissipation proportional to load current is expectable.

Meaning it’s not going to fire.
Ideally a link to something would be good. Is there a way to determine what SCR I’d need with what heat sink combo?

Hi.

If we had useful specifications like voltage, current, phase angle, channel count .... and so on ... we could help you.

Klaus

KlausST said:

Hi.

If we had useful specifications like voltage, current, phase angle, channel count .... and so on ... we could help you.

Klaus

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I don’t think it’s that complicated. It’s mains 230v ac through series wiring to 16 heat lamps running from mains sockets. Each heat lamp is 175w. I intend to put the dimmer directly after the mcb.
If it’s too complicated I’ll sort it myself. Just thought someone could recommend something.

specs
switch 18 heat lamps at 175w each 230Vac = 3150 Watts.

Current = 13.7 A hot, 41 A cold at 1200'K Red heater, more if brighter.

I suggest a 40A 280Vac SSR with AWG16. with a CPU-like heatsink. 1N*m torque on bolts with heatsink grease.

Maybe this one.



Maybe your Chinese one was just missing the necessary heatsink.

D.A.(Tony)Stewart said:

specs
switch 18 heat lamps at 175w each 230Vac = 3150 Watts.

Current = 13.7 A hot, 41 A cold at 1200'K Red heater, more if brighter.

I suggest a 40A 280Vac SSR with AWG16. with a CPU-like heatsink. 1N*m torque on bolts with heatsink grease.

Maybe this one.
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Click to expand...

Thank you for the reply.
How would this work with a dimmer?

Martziniuk said:

Thank you for the reply.
How would this work with a dimmer?

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it won't work with the "Z type ZCS feature but will work fine with the "R" type for random phase

Thank you Tony.
I think you are maybe correct. The heatsink wasn’t great on the Chinese one so maybe I’ll start my search there for simplicity. It did run fine apart from the heat.

Martziniuk said:

I don’t think it’s that complicated. It’s mains 230v

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True, it's not that complicated.
But most important key specification of a triac is "current" and "voltage". None of them we knew before. Load Watts is nothing a triac is specified with.

Regarding current: If it is a pure ohmic load one can calculate: P = V(RMS) x I(RMS) .. Not only that I(peak) = 1.41 x I(RMS) for sinusoidal shape ... but also load behaviour increases current. Incandescent lamps may draw 5x the current when cold .. then when fully ON

Other lamps may have inductive, capacitive or nonlinear behaviour, too.

So - until then - we did not know mains voltage,. Still we can only guess about lamp behaviour.

I'm a professional designer, I work with clear specifications,datasheets, physics and math. Tis resulted in very reliable industrial designs for decades now.

You are free to work with guessing, assumptions ... trial and error. But usually one can do this without eternal assistance, since the result will always be an unreliable design. It may work, but it may fail after a week...or after a year, or fail on environment change like temperature.

So it's your choice how you do your designs and how reliably your designs are working

There are three major reasons for a semiconductor to fail:
* overvoltage, even short spikes in the microseconds
* overcurrent
* silicon over temperatur
You have to consider all of them to get high reliability.

Klaus

Martziniuk said:

Meaning it’s not going to fire.

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You didn't yet reveal what the rated current of the used dimmer module is. Either it's too low or the vendor specification is fake.

FvM said:

You didn't yet reveal what the rated current of the used dimmer module is. Either it's too low or the vendor specification is fake.

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25A. Max 45A.
Being Chinese I can imagine it’s over optimistic. Saying that I’ve been using the same ones on an 8 light 1400w circuit for years.

25 A involves about 30 W triac power dissipation. The heat sink can be expected to run quite hot. Only a triac with bigger heat sink or a fan can solve the problem.

Should do the job?