3000 watts Dimmer for Inductive Load

This is the 3,000 watts Dimmer for inductor load example: the Electric Fan, AC motor, Electric drill, etc. But most general dimmers are used for resistors load only such as a lamp, soldering iron, heating coil, etc. Why our project can do?

The normal dimmer cannot use for inductor load, because of the phase of current and voltage drop across load not same, the current will slow than the voltage by 90 degrees. (Theoretical maximum). If we trig the triac’s gate lead at an angle of normal voltage, but current will lower than the holding current.

How inductive load dimmer works

Figure 1 is a Schematic Diagram of the 3000 watts inductive load dimmer. The Triac-Q2 is the high sensitivity gate types. The C1, R5, and VR2 determined the trigger angle. The VR1 is set at the lowest angle that the Triac Q1 start conducts current.

3000 watts inductive load dimmer

Figure 1 the schematic diagram of this project.

Thus we must sure that adjust VR1 at load fewest works. The capacitor C1 is charged from 0 volts continuously rise.

The Diac-D5 will conduct current when C1 charge to the breakdown voltage of D5.

The first pulse is sent to the gate lead of the Triac Q1 and the sparking voltage in R8 will be the trigger to Q1 and Q2 conduct current.

The one resistance level is made of R4 + VR2/ /R3 + VR1 will charge briefly the current from C1 ( the time is determined by (R5 + R6) C1).

When through this delay range, the Q2 will begin conducting current in the news cycle. Then, the pulse from Q2 will trigger to Q1 until a current of Q1 lower to zero.

The Triac Q2 will stop conducting current. Then, C1 will be charged by these devices (R4 + VR2/ /R3 + VR1).
See Figure 1 again to clearly understanding.

The Zener diode ZD1-ZD4 are used to the overvoltage protection and makes the steady trigger voltage at all time (positive-negative).

The diodes D1-D4 and R1, R2 will discharge the capacitors – C1, in While the time period is zero or the load current is zero.

The R7 and C2 are the damping network to protect sparking current into this circuit.

How to builds

This project have many parts so should make the PCB as Figure 2 shows an actual-size of Single-sided Copper PCB layout.

the PCB layout of this projects
Figure 2 the PCB layout

the components layout
Figure 3 the components layout

It’s like other projects we need completely assemble as Figure 3 show the components layout.


– This project is only ideal, I never tested it. thus if you need to build them please be careful! and not for the beginner!

– They are used with AC220V so safety first.

– When a Triac Q2 works, it will get very hot, so we always use a heat sink on it.

– The inductor L1, we can use the transformer toroidal core, No. TRB 24 x 15 x 10mm, and use the copper wires No. 19 to slowly wind up around core in the same way about 30 times.

The parts you need
C1: 0.1uF 100V, Mylar
C2: 0.1uF 250V, Mylar
D1-D4: 1N4004, 600V,1A Diode
F1: Fuse 6.3A
L1: 100uH___inductor
Q1: 4025Z5__transistor
Q2: 4006L4 or Triac;400V, 3A
R1, R2: 47K, 1W_ Resistors tolerance: 5%

0.25W Resistors, tolerance: 5%
R3: 150K
R4: 27K
R5: 10K
R6: 4.7K
R7: 220 ohms 1W Resistors tolerance: 5%
R8: 1K
ZD1-ZD4: 33V,1W__Zener diode
Other parts_____Heat sink,box,PCB, Fuse, Wires and more.

3 thoughts on “3000 watts Dimmer for Inductive Load”

  1. Схема корявая, содержит множество ошибок работать не будет даже теоретически. Не ведитесь


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