More info on app note 308

[jefnteri]

Posted on October 12, 2004 at 06:18

More info on app note 308

[jefnteri]

Posted on May 17, 2011 at 10:17

I've been looking for a speed control schematic for universal motors that I can use for an assortment of power tools. the current range is from 2 amps to near 15amps on120V./60hz.. I found what appears to be what I'm looking for in app. note 308 in the circuit that uses a sensitive gate triac to drive another one that actually controls the motor. Unfortuunately there are no component values or ST part numbers for the semi's or formulas to calculate them. Also, do I need a snubber across the triac or have you got a good snubberless one for me to use? Any help greatly appreciated.

[ This message was edited by: ETguy on 17-09-2004 13:06 ][ This message was edited by: ETguy on 21-09-2004 11:24 ]

[gaetano]

Posted on May 17, 2011 at 10:17

Hi,

I attached a doc that could help you in snubber(less) issues. Regards, Tanio

[gaetano]

Posted on May 17, 2011 at 10:17

ETguy,

please may you attach the AN308 so I can give a look to it. Thanks&Regards, Tanio

[jefnteri]

Posted on May 17, 2011 at 10:17

Here's AN308. The circuit I'm referring to is Fig.8. Thanks again,ETguy.

[ This message was edited by: ETguy on 21-09-2004 11:51 ] [ This message was edited by: ETguy on 21-09-2004 11:52 ] [ This message was edited by: ETguy on 23-09-2004 06:09 ][ This message was edited by: ETguy on 23-09-2004 06:36 ]

[gaetano]

Posted on May 17, 2011 at 10:17

Hi,

please, be patient a little bit. As this AN was made some years ago, the author is not more available. Neverthless, I am searching in the technical community for triac device to have the info you need. Keep in touch by forum. Regards, Tanio

[benjamincheron9]

Posted on May 17, 2011 at 10:17

Hi dear ETguy,

Let me introduce myself: I work in the ST's application lab in Tours, and I'm responsible on applications based on triacs (Appliances, Ligting, Industrial...). The application note AN308 is actually a general one, giving topologies... The diac selection is easy: you can consider the DB3 part number... Concerning the triac, the selection of the most suitable part number depends on several parameters: - nominal current, inrush current waveform, stalled rotor conditions => thermal management and current rating choice - possible overvoltage after the turn-off => voltage capability - possible stress induced during the turn-off => turn-off commutation capability - EMC requirement => IGT / dV/dt trade-off choice - ... According to the full characterization of the load(s), it is possible to identify the current rating (from 1A to 40A), the voltage rating (from 400V to 800V), the sensitivity (from 5mA to 50mA) and the technology needed... Attached you will find a document summarizing the key parameters of triacs... This document can help, for instance, to calculate the power dissipation, to manage the transient thermal behavior, to anticipate on any turn-off issue (especially with universal motor and its brushes)... The interest of this document is to give the method to select the best triac. I really hope that these few informations will help you... With my best regards, Benjamin Cheron