Solutions summary for inductive load control

AN308

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A.3

New triggering circuit

See Figure 12 part C for the schematic diagram.

A.3.1

Resistive load

No problem over the whole adjustment range.

A.3.2

Inductive load

Operation in the two possible cases:

●

Delay angle

θ > ϕ

Balanced conduction due to good synchronization of the triggering pulses

●

Delay angle

θ < ϕ

For a conduction angle higher than 180°, the TRIAC turns off after the 1st pulse of the

following half-cycle. It is immediately retriggered by the next repetitive pulse. The two

currents are modified until a balance is reached.

A.3.3

Circuit characteristics

Disadvantages of the circuit:

●

Connection by 3 wires - it is necessary to have access to the mains terminals.

●

Power is dissipated permanently by the passive components.

Advantages:

●

Accuracy of the triggering pulses

●

Correct operation for resistive loads

●

No bad operation with inductive loads

●

Power variation over the whole range

●

Good balance between positive and negative current cycles