Lighting SystemsPower System

Basics of the ballast

Unlike incandescent lamps, discharge lamps can not be directly connected to the grid. Before the current was stabilized in some way, they increased and intensified, causing the lamp to overheat and destroy. The length and diameter of the filament in the main incandescent bulb restricts the flow that runs through it and adjusts the light emitted. Instead of a filament, the discharge light uses an electric arc effect, so it needs something called a “ballast” to aid in lighting. Ballasts have three main uses:
     • Provides the correct start-up position because the lamp needs a startup voltage greater than the working voltage
     • Make a combination of the source voltage and the working voltage of the lamp

    • Limit the current to avoid the lamp failure because when the arc appears, the total resistance of the lamp will decrease (negative differential resistance)
    First, the lamp is treated as a non-conducting gas between the two electrodes. The ballast needs to provide a voltage to generate the arc between the two electrodes. This voltage is supplied by the transformer located in the ballast and sometimes it is assisted by a starter to generate high pulse. When the gas in the lamp has been ionized, the resistance of the lamp will drop very quickly, so that the electrode is not overheated. When the current has passed through the gas flow, it will heat up and pressurize the discharge tube. This pressure increases the resonance of the arc current which leads to continued gas heating and pressure boosting. Ballasts need to control the current and voltage so that the lamp is stable at nominal power. Lack of control of the current of the ballast will increase until pressure on the two electrodes will decrease, ionization will switch off and the light will stop working. If the ballast is not suitable they will cause the lamp to work in a non-optimal state. As a result, the lights do not work at the right capacity and will not deliver the right light, and their lifespan will decrease. The ballast must provide the correct rated voltage to start and maintain the arc and the current must be controlled so that the lamp operates at full power.

   Basics of the ballast: In order to choose the ballast for practical applications, it is necessary to pay attention to three types of lamps: the number of lamps in which the ballasts must work simultaneously and the input voltage of the ballasts. Lighting systems. Once the three parameters have been identified, the ballast will be selected based on the following characteristics.
   Input power: That is the total capacity required for both the ballast and the lamp to work as a unit. It is not possible to calculate the input power as the arithmetic of the ballast capacity plus the lamp power as most ballasts do not control the lamp at full rated power. Therefore, the input power is a measure that needs to be measured accurately after determining the correct capacity of the working lamp.
   Ballast capacity loss is the specific loss of ballast power. If this loss is determined then the input power is the sum of this loss plus the lamp power. However, this calculation can lead to errors if we are not sure that the lamp is running at full capacity.

   Input current: It is the nominal current consumption of ballasts and lamps. For most ballasts there is only one input current value specified. For some other ballasts, for example, electromagnetic ballasts for compact fluorescent lamps have work currents, start currents, open currents. It is likely that the start current and open circuit are larger than the current. The largest line must be noted to properly design the circuit of the lighting system, the startup circuit, the protection fuse … otherwise it can cause damage to the system.
   Power Factor PF: The power factor determines the correlation between the two types of power: Ownership measured in kilowatts (KW). It is the work that the system performs in motion, heat production or the like. Incorrect measure in kilovolt-amperes (KVAR). These two types of generators generally produce measured values ​​in kilovolt-amperes (KVA) units. Lastly, the power factor is the ratio between good and fair, KW / KVA.
   The power factor of the ballast determines the conversion efficiency of the current and the current of the power source to that of the ballast and the lamp. The efficient utilization of the current causes the power factor to reach 100%. The power factor is not an indicator of the ability of the ballast to produce light.
Ballasts are designed with high or low PF (or low) or adaptive PF. The high PF type used in commercial lighting has a value greater than 90%. High-PF type ballasts use lower starting currents than low-PF type ones, so the same lighting fixture can be installed in the same place. Low-PF ballasts typically have twice as high starting currents with high PF. They require more wiring because they are less installed in the same branch of the light fixture, which can cause overloading of the network and could be punished by power suppliers.
    Ballast Factors: Because ballasts are an integrated element of the lighting system, they have a direct effect on the flux of light emitted. BF ballast coefficient is the quantity

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