Given a fluorescent lamp, switched on in the circuit of Figure 12.21, the frequency of the applied non-belt voltage is 50 Hz. The following quantities are measured: total (mains) voltage U = 228.5 V, current I = 0.60 A. Fluorescent lamp voltage U = 84 V, ohmic resistance of the ballast choke Rd = 26.3 Ohm. The fluorescent lamp should be considered as an ohmic resistance. Answer the following questions and complete the tasks: 1. What inductance L does the inductor have? 2. Determine the value of the phase shift φ between voltage and current. 3. What active power P is released in the circuit? 4. The choke, in addition to current limitation, has another important function. Name and explain it. Note. The starter S has a contact that closes shortly after switching on, then opens and remains open. 5. Draw a curve of the luminous flux emitted by the lamp versus time (with a quantitative scale along the time axis). 6. Why does the lamp burn all the time, although the applied alternating voltage passes through zero at certain intervals? 7. For fluorescent lamps of the type described, a capacitor with a capacity of approximately 4.7 μF can be connected in series to the choke. How does this affect the operation of the lamp and for what purpose is this feature provided?
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