Low power consumption for high power output

[jorat134612]

I'm looking to do a little home project. I want to do my our digital heating control thermostat. So, I'm looking for high power low dissipation electronic component. I don't want to use relay because they are noisy and I want to be able to modulate the voltage too. So far, everything I have seen have an almost direct ratio of 1W for 1A control. On a typical electric header of 40A @ 120VAC, we will have a dissipation of 40W which correspond of a standard light bull. So, at 4800W for a electric header, we have a efficiency of 0.83% which for me is a lot. This also translate in a thermal dissipation which need to be dissipate. I will like to have all my setup fitted in a standard electric light switch box. With a 40W of thermal power to dissipate, it's hard to fit it inside such a little box and also have a room temperature sensor in there too. For what I know it's not possible to find something with a lower power consumption as long as we stick to silicon triac as silicon triac.

So any suggestion of a very high power switch with low power/low dissipation control modulator?

 

[goldsmith]

Dear jorat134612
Hi
You can use from triacs which have low dissipations if you fire it correctly .
Best Lucks
Goldsmith

 

[mister_rf]

For this type of application you may use a time proportioned system that cycle time to proportion the output value. This ON/OFF control is one of the simplest types of control to implement and it works by setting up a hysteresis band and if the cycle time is set for example to N seconds, a system calling for 50% power will have the output on for N/2 seconds and off for N/2 seconds. As long as the power value doesn't change, the time values wouldn't change. Over time, if needed the power is averaged to the 50% commanded value, half on and half off. If the output power needed let’s say to be only 25%, ( for the same N second cycle time), then the output would be on for N/4 seconds and off for the remaining 3N/4 seconds.
In practice you can use a microprocessor based controller system and for the power switch some solid state switching devices like an SSR or triacs.

 

[tpetar]

I'm looking to do a little home project. I want to do my our digital heating control thermostat. So, I'm looking for high power low dissipation electronic component. I don't want to use relay because they are noisy and I want to be able to modulate the voltage too. So far, everything I have seen have an almost direct ratio of 1W for 1A control. On a typical electric header of 40A @ 120VAC, we will have a dissipation of 40W which correspond of a standard light bull. So, at 4800W for a electric header, we have a efficiency of 0.83% which for me is a lot. This also translate in a thermal dissipation which need to be dissipate. I will like to have all my setup fitted in a standard electric light switch box. With a 40W of thermal power to dissipate, it's hard to fit it inside such a little box and also have a room temperature sensor in there too. For what I know it's not possible to find something with a lower power consumption as long as we stick to silicon triac as silicon triac.

So any suggestion of a very high power switch with low power/low dissipation control modulator?

If you whant to have no dissipation of power and you have high requirements for current, my opinion for this is to use contactors. Only contactors can safely and without dissipation switch high loads. There is of course low noise or no noise contactors, standard contactors have noise when switching. There is one or three phase contactors with contacts variations like variants. Contactors can have low voltage coils like 12V, 24V, and HV 110V, 220V. Price of low noise contactors is higher then price of standard contactor.

Triac dissipate 20-40W. If you plan to use triac my suggestion is to use BTA... serie or similar with insulation of case. BTA.. serie can have 40-60A,... and can go up to 800V, TOP3 case is available. Important is to use triac with zero crossing detection control, in order to pass all electricity to heater. Triac can do the job of course. Very often known as solid state relay in sealed case. With triac you can even regulate and control inrush or peak current on electrical installation when switching heater equipment or oven or other heavy demand consument.

Contactor can switch off all wires, phase, null, ground, or all three phase + null. Triac switch off just one wire, you must use several triacs for three phase switching. You can also use appropriate soft start control with contactors.

For solution I suggest to use low noise or no noise contactor. Take in mind safety of device and safety of environment and house and people.

 

[jorat134612]

This is very interesting! And I'm very temped to get a contactor in there, but zero noise contactor is really hard to find and it has to be zero noise. The thermostat will be retrofitted in existing thermostat socket and therefor will be installed in rooms, living-room, kitchen, and I don't want to hear the clicking noise of the relay when I go to bed.

So, zero noise relay are hard to find and usually the zero noise relay are called solid state relay which is just a triac.

Triac will always dissipation of 20W to 40W which is too much for what I want to do.

Are we screwed? Maybe not..

What I found is if the triac or transistor is made out of another type of material (https://en.wikipedia.org/wiki/List_of_semiconductor_materials). The problem? I can't find a triac or a transistor that is made from something else than silicon and has a better efficiency. Maybe you guy know more on this?

Also, I know it's a little science fiction, but superconducting transistor could also work.. I just haven't find one yet...

 

[FvM]

You already realized, that triacs have the said power dissipation by design, simply caused by the voltage drop.

Besides contactors, that have been discussed, "anti"-serial MOSFET combinations can achieve considerably lower power dissipation. If switching speed isn't an issue, photovoltaic opto couplers are the most simple way to provide the required gate voltage. Commercially available AC/DC solid state relays offer similar features.