Logic level and Snubberless TRIACs

AN439

14/16

Figure 14.

TRIAC turn-off behavior for universal motors

●

controlled by a diode bridge (see Figure 15). The current variation at turn-off is then

only limited by the parasitic inductance of the line and the diodes bridge circuit.

Figure 15.

Inductive load controlled by a diode bridge

Table 3.

TRIAC choice for universal motor control

Power

Mains voltage

and frequency

Load

current

1.

Standard

TRIAC

Snubberless

TRIAC

600 W

220 V / 50 Hz

3 A rms

6 A

3.5 A/ms

BTx10-600B

BTx06-600BW

110 V / 60 Hz

6 A rms

10 A

7 A/ms

BTx16-600B

(2)

BTx08-600BW

1200 W

220 V / 50 Hz

6 A rms

10 A

7 A/ms

BTx16-600B

(2)

2.

This type specified at 7 A/ms minimum can be too small. Certain applications could need 25 A standard

TRIAC.

BTx08-600BW

110 V / 60 Hz

12 A rms

16 A

15 A/ms

BTx40-600B

/ BTx41-600B

BTx24-600CW

Average slope

of the TRIAC

current

I

T

V

T

dI/dt

Average slope

of the TRIAC

current

I

T

V

T

dI/dt

V

Mains

-

+

Inductive load

(motor, valve …)

L

R

V

Mains

-

+

Inductive load

(motor, valve …)

L

R