Saturday, July 04, 2020

Triac Operates Dimmer, Electronic Dimmer

Dimmers
  • Different lamps/luminaires produce light with constant brightness once they are switched on.
  • For the following spots, the variation of brightness of the lamps is required.
For (i) Photo studios (ii) Stage (iii) Drama theatres (iv) Decorations (v) Various functions.
  • The device for controlling the brightness is a "Dimmer".
  • Dimmer is an electrical and or electronics device. It basically changes the current or voltage which is the cause of varying brightness of luminaries.
  Let us study the circuit arrangements and operation of these dimmers.
1. Variable Resistance Type Dimmer
1.1 Resistance Type Dimmer
1.2 Salt Water Dimmer


2. Dimmer Transformer
2.1 Autotransformer Dimmer
2.2 Two Winding Transformer Dimmer

3. Electronic Dimmer

  • Electronic dimmers are very compact and handy.
  • These circuits make use of solid state devices like SCRs, TRIAC, DIAC.
  • These are used to control the intensity of lamps.
  • In comparison to resistance control dimmer, the power loss in this system is negligible,
These are two types of circuits possible hence two types are possible
  1. Thyristor operated dimmer
  2. Triac operated dimmer
3.1 Thyristor operated dimmer
3.2 Triac Operates Dimmer

Circuit Diagram of Triac Operates Dimmer

Triac and Diac are used to change the intensity (brightness) of the lamp.
Operation of Triac Operates Dimmer
  • The resistance R1, and capacitor C1 are connected in series.
  • The capacitor is made to charge through the Ri resistance.
  • When the voltage across reaches above the breakover voltage of DIAC, it starts conducting.
  • The voltage across the capacitor now gets applied to TRIAC gate and the TRIAC is turned ON. The charging of the capacitor can be controlled by the variable resistor R1, which indirectly controls the firing delay of TRIAC.
  • Thus the intensity i.e. brightness of the lamp can be controlled.
Application of Triac Operates Dimmer

  1. Stage
  2. Theater.

Friday, July 03, 2020

Thyristor Operated Dimmer, Electronic Dimmer

Dimmers
  • Different lamps/luminaires produce light with constant brightness once they are switched on.
  • For the following spots, the variation of brightness of the lamps is required.
For (i) Photo studios (ii) Stage (iii) Drama theatres (iv) Decorations (v) Various functions.
  • The device for controlling the brightness is a "Dimmer".
  • Dimmer is an electrical and or electronics device. It basically changes the current or voltage which is the cause of varying brightness of luminaries.
  Let us study the circuit arrangements and operation of these dimmers.
1. Variable Resistance Type Dimmer
1.1 Resistance Type Dimmer
1.2 Salt Water Dimmer


2. Dimmer Transformer
2.1 Autotransformer Dimmer
2.2 Two Winding Transformer Dimmer

3. Electronic Dimmer

  • Electronic dimmers are very compact and handy.
  • These circuits make use of solid state devices like SCRs, TRIAC, DIAC.
  • These are used to control the intensity of lamps.
  • In comparison to resistance control dimmer, the power loss in this system is negligible,
These are two types of circuits possible hence two types are possible
  1. Thyristor operated dimmer
  2. Triac operated dimmer
3.1 Thyristor Operated Dimmer
  • If we compare the power loss in such type dimmer with resistance type dimmer it is negligible.
  • SCR (or thyristor) is used to control the phase angle i.e. voltage applied to the lamp which controls brightness of the lamp.
  • The circuit consists of diodes D1, D2, D3, D4, forming bridge rectifier. When rectified output voltage of bridge rectifier increases, capacitor C1 is charged.
  • The voltage across the capacitor increases till it causes zener diode D5 to conduct. When zener diode conducts, the SCR is turned ON.
  • The capacitor C1 now discharges through SCR. The SCR is turned OFF when this current comes to zero. The combination of R1 and C1 decides the conduction current of SCR.
  • Thus voltage applied to the lamp is varied, hence the lamp intensity can be controlled.
Following are waveforms of voltage applied to the lamp.
1st case : Brightness is maximum.
2nd case : Brightness is moderate.
3rd case : Brightness is minimum.
  • Thus by this dimmer the brightness is controlled from maximum to dimming gradually to minimum
Application of Thyristor Operated Dimmer
  1. Used in stage
  2. Drama theatres
  3. and for programs.
3.2 Triac Operates Dimmer

Wednesday, July 01, 2020

Two Winding Transformer Dimmer, Light Dimmers

Dimmers
  • Different lamps/luminaires produce light with constant brightness once they are switched on.
  • For the following spots, the variation of brightness of the lamps is required.
For (i) Photo studios (ii) Stage (iii) Drama theatres (iv) Decorations (v) Various functions.
  • The device for controlling the brightness is a "Dimmer".
  • Dimmer is an electrical and or electronics device. It basically changes the current or voltage which is the cause of varying brightness of luminaries.
  Let us study the circuit arrangements and operation of these dimmers.
1. Variable Resistance Type Dimmer
1.1 Resistance Type Dimmer
1.2 Salt Water Dimmer


2. Dimmer Transformer
In this category there are two transformers
  1. Auto transformer dimmer
  2. Two winding transformer dimmer
  • The dimming can be obtained by varing the voltage applied to the luminary. The variable voltage can be obtained from transformers which are known as dimmer transformers. These are used in theater lighting.
  • Explanation of these two types is given below :
2.1 Autotransformer Dimmer
2.2 Two Winding Transformer Dimmer
Types of Two Winding Transformer Dimmer
  1. Normal two winding transformer dimmer
  2. Coil rotation transformer dimmer
  • Let us study the construction and operation of these two types.
2.2 (a) Normal two winding Transformer Dimmer
It is a normal we winding transformer having tappings on the secondary winding.

Circuit Diagram of Normal two winding transformer dimmer
  • A tap-changer rotary sector is used to select the tappings.
  • So a variable voltage is obtained on secondary to which (L1) (L2)... etc. luminaires are connected.
  • Hence tap changer changes the brightness of the lamps.
Application of Normal two winding transformer dimmer
  1. Drama stage
  2. Theatres
2.2 (b) Coil-rotation Transformer Dimmer

Circuit Diagram of Coil-rotation transformer dimmer
Operation for the system of Coil-rotation Transformer Dimmer
  • A motor is used to rotate the winding relative to the fixed secondary winding.
  • Due to rotation, the flux linkage between primary and secondary changes.
  • When the coil axis are parallel to each other, the flux linkage is maximum. Thus maximum e.m.f. is induced in the secondary coil.
  • The luminaries receive maximum voltage and glow bright.
  • If the primary coil is rotated such that its axis is 90° to the secondary coil, the flux linkage is minimum.
  • Thus minimum e.m.f. is induced in the secondary coil.
  • The luminaries receive minimum voltage and glow dim. For the angular positions between 0° to 90°, the brightness increases gradually.
  • The motorized set can be operated through remote control. Since primary is a rotating member, the current is fed through flexible connections as shown.
Application of Coil-rotation Transformer Dimmer
  1. Stage
  2. Theatres.
3. Electronic Dimmer
3.1 Thyristor operated dimmer
3.2 Triac Operates Dimmer

Tuesday, June 30, 2020

DOL Stater Wiring Connection Step by Step, DOL Stater Wiring

DOL Stater
  • A DOL starter (or Direct On Line starter or across the line starter) is a method of starting of a three phase induction motor. In DOL Starter an induction motor is connected directly across its three phase supply, and the DOL starter applies the full line voltage to the motor terminals. Despite this direct connection, no harm is done to the motor. A DOL motor starter contains protection devices, and in some cases, condition monitoring.
3 Phase Motor Starter with Overload Protection
  • When a motor draws excessive current to meet the load requirements such that this load requirement goes beyond the rated limit, this is known as overload.
  • Thermal overload protection is a type of security when the motor draws over current or excessive current and causes overheating of the equipment. Overload is also the type of over current.
  • So overload relays are employed to limit the amount of current drawn. But that does not mean that protects the short circuit.
  • Fuse or MCB used in the system protects the over current. Overload protection opens a circuit at relatively low currents that are a little higher than the rating of the motor.Overload currents are likely to damage if they persist for a long time, i.e. it will not trip if a high value of current flows for a short period such as starting of the motor.
  • We often provide overload protection via an overload relay. Overload relays may be solid-state devices with adjustable trip setting also called as the electronic relay or by interacting with related temperature sensors called as a thermal relay or if only operates for excess current flow then called as a magnetic relay.
  • For most motors, the maximum rating of the overload protection device is 125% of the full load ampere rating.
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Auto Transformer Dimmer, Dimmer Transformer

Dimmers
  • Different lamps/luminaires produce light with constant brightness once they are switched on.
  • For the following spots, the variation of brightness of the lamps is required.
For (i) Photo studios (ii) Stage (iii) Drama theatres (iv) Decorations (v) Various functions.
  • The device for controlling the brightness is a "Dimmer".
  • Dimmer is an electrical and or electronics device. It basically changes the current or voltage which is the cause of varying brightness of luminaries.
  Let us study the circuit arrangements and operation of these dimmers.
1. Variable Resistance Type Dimmer
1.1 Resistance Type Dimmer
1.2 Salt Water Dimmer


2. Dimmer Transformer
In this category there are two transformers
  1. Auto transformer dimmer
  2. Two winding transformer dimmer
  • The dimming can be obtained by varing the voltage applied to the luminary. The variable voltage can be obtained from transformers which are known as dimmer transformers. These are used in theater lighting.
  • Explanation of these two types is given below :
2.1 Autotransformer Dimmer

Circuit Diagram Of Autotransformer Dimmer


Operation of Auto transformer dimmer
  • A.C. supply connected to the single winding of a transformer. Varying the knob a variable voltage is obtained from the other side to which lamps L1, L2 , L3 , L4 etc. are connected. The lamps get the variable voltage for changing the brightness of lamps.
Advantages of Auto transformer dimmer
  1. Simple operation
  2. Reliable operation
  3. Equipment cost low (single device)
  4. No maintenance
  5. Many lamps can be controlled simultaneously.
Disadvantages of Auto transformer dimmer
  • Due to manual operation the electrician is engaged all the while.
Application of Auto transformer dimmer
  1. Stage lighting
  2. Drama theaters
  3. Recreation halls
  4. Exhibition-to attract visitors.
2.2 Two Winding Transformer Dimmer

3. Electronic Dimmer
3.1 Thyristor operated dimmer
3.2 Triac Operates Dimmer