BDS Power Systems and Standby Powering 2 — Questions and Answers
Question 1: What is the standard frequency of AC power delivered by HFC cable plant power supplies in the United States?
- 50 Hz
- 400 Hz
- 60 Hz (Correct answer)
- 1 kHz
Correct answer: 60 Hz
HFC cable plant power supplies in the U.S. operate at 60 Hz, matching the standard North American utility grid frequency.
Question 2: What is the purpose of output fusing in a cable plant power supply?
- To regulate the output voltage to the correct level
- To amplify the RF signal passing through the supply
- To prevent lightning surges from entering the headend
- To protect the coaxial plant from damage due to overcurrent conditions (Correct answer)
Correct answer: To protect the coaxial plant from damage due to overcurrent conditions
Output fuses open when current exceeds a safe level, protecting the coaxial cable and connected equipment from damage caused by shorts or excessive current draw.
Question 3: When measuring AC voltage on an energized coaxial cable in an HFC outside plant, which instrument should be used?
- Standard household voltage tester
- True RMS AC voltmeter rated for use on RF-carrying conductors (Correct answer)
- DC clamp meter
- Ohmmeter connected to the outer shield
Correct answer: True RMS AC voltmeter rated for use on RF-carrying conductors
A true RMS voltmeter designed for RF-carrying coaxial cables accurately measures AC plant voltage while safely handling the simultaneous presence of RF and power signals.
Question 4: What is the typical maximum output current rating for a standard HFC outside plant power supply?
- 1-2 amperes
- 5-10 amperes
- 15-20 amperes (Correct answer)
- 50-100 amperes
Correct answer: 15-20 amperes
Standard HFC cable plant power supplies are typically rated at 15-20 amperes at 60-90V AC, providing enough current to power multiple active devices on a cable segment.
Question 5: What is a 'power hog' in the context of HFC cable plant powering?
- An active device that draws significantly more current than its specification (Correct answer)
- A power supply that dissipates excessive energy as heat
- A device that causes elevated RF interference levels
- A battery string that cannot hold a full charge
Correct answer: An active device that draws significantly more current than its specification
A 'power hog' is an active field device such as an amplifier that draws more current than its rated specification, potentially overloading the power supply serving that segment.
Question 6: What does 'power budget' refer to in HFC outside plant design?
- The financial cost of operating the cable plant power system
- The RF signal power level available at the end of a cable run
- The total current capacity of a power supply allocated across all powered devices on a segment (Correct answer)
- The generator fuel consumption rate during a utility outage
Correct answer: The total current capacity of a power supply allocated across all powered devices on a segment
Power budget involves calculating the combined current draw of all active devices on a power supply segment to ensure the total does not exceed the supply's rated output capacity.
Question 7: What is the primary role of a voltage regulator in an HFC cable plant power supply?
- To amplify RF signals passing through the supply housing
- To maintain a stable output voltage despite variations in utility input or connected load (Correct answer)
- To convert single-phase utility power to three-phase output
- To limit battery charge rate and extend battery service life
Correct answer: To maintain a stable output voltage despite variations in utility input or connected load
A voltage regulator keeps the plant output voltage constant even when utility input voltage fluctuates or load conditions change, ensuring reliable powering of active equipment.
BDS Power Systems and Standby Powering 2
What is the standard frequency of AC power delivered by HFC cable plant power supplies in the United States?