In systems where two or more sources operate in parallel with a primary source, the sources must have compatible frequency, voltage, and waveform.

In systems where two or more sources operate in parallel with a primary source, the sources must have compatible frequency, voltage, and waveform.

• A. They must have compatible frequency, voltage, and waveform
• B. Only frequency must match
• C. Only voltage must match
• D. No restrictions

Answer: (A)

When several sources operate in parallel with a primary source, their outputs must be synchronized in frequency, voltage magnitude, and waveform. If the frequencies don’t match, the bus voltage will continually chase different reference speeds, driving large circulating currents between sources that heat equipment and can trip protections. If the voltages aren’t the same, one source will push power into another, again creating unwanted currents and stress on the sources and wiring. If the waveforms aren’t identical, harmonics and distortions flow between sources, upsetting the bus voltage and potentially causing overheating or protection trips. Matching all three—frequency, voltage, and waveform—lets the sources share load safely and the system stay stable and predictable. In practice, paralleling requires precise synchronization so there is no circulating current and the power can be shared evenly.

When several sources operate in parallel with a primary source, their outputs must be synchronized in frequency, voltage magnitude, and waveform. If the frequencies don’t match, the bus voltage will continually chase different reference speeds, driving large circulating currents between sources that heat equipment and can trip protections. If the voltages aren’t the same, one source will push power into another, again creating unwanted currents and stress on the sources and wiring. If the waveforms aren’t identical, harmonics and distortions flow between sources, upsetting the bus voltage and potentially causing overheating or protection trips. Matching all three—frequency, voltage, and waveform—lets the sources share load safely and the system stay stable and predictable. In practice, paralleling requires precise synchronization so there is no circulating current and the power can be shared evenly.