triac three-phase control

Rafil Nugamanov · ‎2017-11-19

Posted on November 19, 2017 at 11:24

Hi!

I collect a three-phase control circuit (6kW).

I want to use BTA16 (Snubberless and standard Triacs)

Whether correctly I understand, that for type Standard it is necessary to include in parallel TVS a diode. And for the Snubberless TVS type, the diode will be superfluous (because it is already built in)?

Thank you. Sorry for my english.

#triac #tvs #ac-motor-control

Benoit RENARD · ‎2017-11-21

Posted on November 21, 2017 at 11:04

Hello Rafil,

In both cases - Standard and Snubberless - no need of any TVS diode in parrallel.

Standard type is a four quadrants Triac (see application note AN4363 about 'How to select the Triac, ACS, or ACST that fits your application', section 3).

Snubberless Triac is a three quadrants Triac (No QIV operation), but with improved immunity to dV/dt and turn-off commutation.

Let me know if you need more details,

Benoit

Rafil Nugamanov · ‎2017-11-21

Posted on November 21, 2017 at 22:05

Hi

Benoit!

Thanks for answering.

I got acquainted with AN4363 (Figure 9. Triac overvoltage protection by MOV (a) or Transil (b)). I want to apply the protection scheme Figure 9 (c) for my application.

Also, I got acquainted with AN1966 (TRIAC overvoltage protection using a TransilTM), described for protection using a TVS diode, instead of the Snubberless circuit.

Do you propose, with the Snubberless type, to abandon the protective circuit? And with the Standard type, use protection.

Maybe I do not understand something correctly.

Benoit RENARD · ‎2017-11-24

Posted on November 24, 2017 at 09:30

Hi Rafil,

Regarding protection aginst voltage surges, no difference between Standard and Snuberless (only differences on quadrants, immunity and turn-off commutation as explained).

For the protective circuit against overvoltage surges, two ways:

- Implement a Transil between A2 and G to trigger the Triac when the surge voltage reaches the Transil breakover voltage (VBO). You are right, the AN1966 is a good start to design this circuit. Note that in this case the Triac must absorb the induced overcurrent.

- Use a MOV in parallel of the Triac (between A1 and A2), to clamp the voltage surge below the maximum voltage the Triac can sustain in non-repetitive (VDSM / VRSM parameter). For example, a 800 V Triac can sustain a maximum of VDSM = 900 V. Example of a MOV could be S14K420 (need to withstand your 3-phase voltage).

Let me know if you need more details on both solutions,

BR

Benoit