Fire Pump Run Test Operator Certification Practice Test

Voltage tolerance for a motor during run testing is the allowed deviation from the nameplate voltage. The accepted range is 5% below to 10% above the rated value. This asymmetric tolerance reflects real-world conditions: under-voltage (drops) can occur due to load and supply sags, and if voltage falls more than about 5%, the motor may struggle to develop full torque or stall. Over-voltage, while less common, can happen briefly due to supply spikes and wiring characteristics, and up to about 10% is generally tolerated without immediate damage. For a motor rated at 480 V, that means an acceptable range from about 456 V to 528 V. When measuring, consider the voltage at the motor terminals under normal running conditions and account for any voltage drop along feeders. Tighter tolerances (like 2% or 1%) or a symmetric ±10% range are not typically used in this context because they don’t align with the practical voltage swings seen in service.