Dimming

Question 1

Three types of electronic dimmer circuit designs

Answer 1

SCR/forward phase control
Reverse phase control
Sinewave dimmers

Question 2

SSR

Answer 2

Solid state relay, made of pair of SCRs to regulate power
Two SCRs connected I parallel but opposite directions in a circuit
Solid state device that regulates ac current in both directions

Question 3

SCR

Answer 3

Silicon controlled rectifiers
Type of thyristor(solid state latching relay) that conducts electricity in one direction only
Pair make up a solid state relay

Question 4

Forward phase control dimming- how it works

Answer 4

Rather than increasing or decreasing voltage, scr dimmer increases and decreases power by regulating the duty cycle(on/off time), chopping up the sinewave.
Controller card detects incoming signal(DmX512/Ethernet) decodes it, and produces pulse-width modulated signals in sync with the dimmers power phase to tell each SSR when to activate.
During each half cycle of the AC sinewave, the dimmer controls output by varying how long the dimmer waits before it activates.
Circuit automatically deactivates each time the wave passes through zero
Forward-phase control dimming

Question 5

Advantages of forward phase control dimming-

Answer 5

Fairly simple and very reliable
Effective way to do incandescents
Capacities of 1.2k-12kw at 120V, and 24k at 240V

Question 6

Disadvantages of phase control dimmers

Answer 6

1. Nonlinear loads, current not in proportion to the voltage, when dinner they draw current during only part of each line cycle. This Creates harmonic distortion of the mains current. Harmonic currents add up on the neutral
2. On/off switching off the SCRs creates vibrations in the lamp which produces buzz, especially at 66% abd33%.
   - -dimmers use toroidal filters commonly called chokes, which round of the abrupt rise of voltage and inrush current with each half cycle
   - - the bigger the choke, the longer the rise-time and less buzz
   - - dimmers with 800us riser time much quieter than 350us, lamp noise not eliminated
3. Vibration reduces lamp life
4. Chokes cause hear loses that result in typical scr recurrence of 95%
5. Chokes weigh a lot
6. With very small filament lamps phase control dimming-at 60 hz can cause flicker at certain frame rate and dimmer settings

Question 7

Reverse phase control dimming

Answer 7

Commonly igbt dimming
Igbt- insulated gate bipolar transistor, high speed switch device used in power electronics
Instead of chopping front of sinewave, chips back.
Current rides smoothly up to the cut off point
Elongates the need for chokes, dinner smaller and lighter
3V less voltage drop
Reduces lamp noise
Rise time or fall time used by igbt can be varied by electronics, often automatically reduced to counteract a ride in dinner temperature

Question 8

Disadvantages if reverse phase control

Answer 8

Lamp noise may increase if dinner temperature increases
Igbt dinner harmonics and excessive neutral current are about the same as forward phase control dimmers
Likelihood of receiving flicker is the same
Strand lighting and entertainment technologies make igbt dinner packs and strips in 1.2k and 2.4k and small stand alone
Cost about the same

Question 9

Bak Pak dimmer/ strand light pack

Answer 9

Intelligent power systems
Small stand alone 750w or 1200w igbt dimmer
Can be set to either forward it reverse phase dimming
Completely silent
Dmx or no dmx flicker effects
Use intelligent effects network coupler to coordinate effect between multiple Bak Paks by using one as a dnx512 transmitter

Question 10

Sinewave dimmer availabikiy

Answer 10

Available for permanent installation, not portable racks or packs
Trans sst series in 1.2 2.4
Etc sensit sinewave in 2.4
Larger sizes in Europe
Cost three times SCRs
Not yet used in film

Question 11

Sinewave dimming

Answer 11

Produce a full sinewave
Electronic version of old autotransformer or variac
Varies the rms voltage by using igbt circuit that operates at a very high speed 47-50khz
Amplitude of RNs vrage controlled by pulls wave modulation within this very narrow time frame
Igbt on and off at full voltage, because period is so short, and circuitry included to smooth the wavegorm, load sees a continuous waveform
Elim I Nate’s lamp noise
Because current is drawn during entire cycle, does not create current harmonics
Les that 1% harmonic distortion
Have unity powr factor 100%
Transparent to the load
Can deliver power to the load almost as if direct connection to or line
Allows control of neon, LEDs, fans small motors

Question 12

ETC sensor dimming system

Answer 12

modular dimmer system, dimmer modules slide in and out of the rack

Question 13

CEM

Answer 13

Control electronics module