Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Thyristor choice?

Status
Not open for further replies.

Jadeit

Member level 5
Joined
Feb 10, 2017
Messages
84
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
2,191
I need to control the power of the heating element 230V 15A.
Choice of triac, optotriac and MCU.
I will use either MOC3083 if I decide to control after half-waves, ie switching at zero or
MOC30452 .
Theoretically, a triac is enough BTA16, however, for almost the same money I can have
BTA26800B or even BTA40-800B in RD91.
Is it important to use a more powerful triac, thus reducing the losses on the triac, or is it necessary to switch more triacs to increase power and is it not worth it?
Is a snubber required to switch the resistance heating element?
 

Hi,

don´t half wave control, do full wave.

See the ON-State characteristics diagram: At about 15V the voltage drop is:
BTA16: 1.4V
BTA26800B: 1.25V
BTA40-800B: 1.20V

so the power dissipation is just reduced by 14%
Paralleling will spread the power dissipation to the triacs only if silicon is at equal temperature.
In reality I expect that one triac carries most of the current and the others almost nothing.

But don´t go close to the limit. I´d use at least a 20A rated one.
Mind to keep temperature within specified range.

***
If you want clean regulation, then use several loads: 1A / 2A / 4A / 8A and switch them individually. Binary style.

Klaus
 

Thank you for the information. I will use BTA40, the case comes best for my cooling and allows direct power supply without PCB.
It is a muffle furnace, so I can only switch on the side and especially the rear heating.
Each winding approx. 15A.
Control to the required temperature and especially dT / dt (rate of temperature rise over time).
 

Hi,

One maybe useful point:
There are triacs with isolated package, so isolated mounting in a heatsink is easy.

Klaus
 

If I'm not mistaken and the documentation is not lying, then BTA are always isolated A means isolated non-isolated means B BTB
See page 10 datesheet BTA40 800B
 

Hi,

You are right.
I had the black plastics coated tab in mind. But these triacs have the isolation internally.

Klaus
 

any scr or triac has an on drop, 0.8 - 1.0v for an scr, higher for a triac, 15A rms x 1.25v for a triac = 19 watts, you need a decent heatsink for this.
--- Updated ---

ideally control with full 20mS cycles if you can, failing that symmetric half cycle control.
 

OK thank you all.
I have ordered BTA40-800b in RD-91 case

I'll ask about Snubber again
So .
Load is 3,4kW heater (helix Kanthar wire ) max temp 1300C ,
Triac BTA40
Driver: optotriac MOC3083 with zerro cross detector.
Do you recommend using Snubber?
If Yes. What parameters?

For smal Triac BTA16 and general Load I use 10nF 630V PP + 33 Ohm resistor, but I'm not sure here?
Plus case RDS-91 The RC should probably come directly to the BTA terminals.
Does it possibly make sense to add RC Snubber to the MOV?
 

depends on inductance of load, 100nF & 33 ohm a good starting point, right across triac, mov needs none.
 

If I apply to kanthal heating as an air coil parasitic induction can be expected 6,7 uH and parasitic capacitance 12pF.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top