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Lead Contents

Difference between Triacs and Thyristors

FAQ No. FAQ02153

Primary Contents

Question

What is the difference between triacs and thyristors?

Answer

They are essentially the same in terms of resistive loads. For inductive loads, however, back-to-back thyristors are effective.
Thyristors connected back-to-back or a triac can be used for Solid-state Relay switching elements.

Thyristors and the triacs differ in their characteristics to enable the elements to adjust to a rapid rise or fall.

These characteristics are expressed as dv/dt (unit: V/ μs). The dv/dt value for thyristors is greater than the value for triacs.

Triacs help downsize Solid-state Relays because they can sufficiently perform switching for motors of up to the 3.7-kW class with inductive loads, and one triac element provides functionality equivalent to two thyristors connected back-to-back.

Note:dv/dt is the rate of voltage rise.

Resistive loadInductive load
40 A max.Over 40 A3.7 kW max.Over 3.7 kW
TriacOKOKOKNot as good
Two thyristorsOKOKOKOK