Electrical fundamentals
Generator electrical specifications describe different parts of performance. Watts measure real power, volts measure electrical potential difference, and amperes measure current. Reading these together helps explain what a generator can supply and what connected equipment requires.
In this topic
Watts, volts, and amps
The difference between power, voltage and current, with correct DC and single-phase AC formulas.
ElectricalRunning watts vs. starting watts
How steady demand differs from startup demand, and how to avoid double counting motor starting watts.
ElectricalKilowatts vs. kilovolt-amps
Real power, apparent power and power factor, including single-phase and balanced three-phase formulas.
ElectricalGenerator total harmonic distortion
What generator THD measures, how nonlinear loads affect it, and why voltage regulation is a different specification.
Units and relationships
In DC circuits, power is voltage multiplied by current. For single-phase AC, RMS volts multiplied by RMS amps gives apparent power; real power also depends on power factor. Confusing watts with volt-amperes can understate current demand. [1]
| Topic | Question it answers |
|---|---|
| Watts, volts and amps | How do the basic electrical quantities relate? |
| Running and starting watts | Why can an operating load be harder to start? |
| Kilowatts and kilovolt-amperes | How do real and apparent power differ? |
| Total harmonic distortion | How closely does the waveform resemble a sine wave? |
Steady operation and changing loads
A running-power total describes demand once equipment is operating. Motor starts and other sudden changes add a transient requirement. Generator sizing must consider both the sustained load and the response to the starting sequence. Acceptable voltage and frequency changes are part of that evaluation. [2]
Power quality
Voltage regulation, frequency behavior and harmonic distortion describe different properties. One favorable specification does not establish the others. The articles in this section define these terms and connect them to generator ratings, load calculations and alternator behavior.
Sources and further reading
- Keysight — Power-quality measurement definitions ↗www.keysight.com
- Generac — Essential guide to power-system sizing ↗www.generac.com
Use the manual and nameplate for the exact model. Local requirements and site conditions take precedence over general examples.