When paralleling an incoming alternator with the bus manually, the synchronizing lamps grow dim and become totally darkened as the synchroscope pointer slowly approaches the 12:00 position while rotating in the fast direction. What does this indicate?
• Synchronizing lamps behavior (bright vs dim vs dark) and what it tells you about phase angle • Synchroscope pointer position (12 o’clock) and direction of rotation (fast or slow) • Required conditions for safely closing the circuit breaker when paralleling alternators (frequency, voltage, phase)
• When synchronizing manually, what combination of lamp condition and synchroscope indication shows that the incoming alternator is almost exactly in phase with the bus? • What does a fast-moving pointer near 12 o’clock tell you about the frequency difference and phase relationship between the incoming alternator and the bus? • Under which condition would closing the breaker cause the least shock or disturbance to the system: lamps bright, lamps dark, or lamps flickering slowly?
• Verify what all lamps dark (or very dim) simultaneously signifies about the phase angle (nearly zero° or nearly 180°?) • Confirm what a fast rotation of the synchroscope pointer indicates about the incoming alternator’s frequency relative to the bus (higher or lower?). • Review the standard practice: the breaker is closed when the pointer is approaching 12 o’clock in the slow direction and lamps show the system is nearly in phase—compare that to what is described in the question.
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