by Steven Baker (bakersj) 11-30-2009 10:52 AM - edited 03-12-2010 08:54 AM
Proper sizing is important. A genset under-sized for the application can fail to start or run the site's electrical loads. Adding additional storage room for larger or additional gensets, where none was initially planned or none can be added, can be costly. Also, over-sizing your genset can lead to lightly loaded engine conditions, which can result in wet stacking.
How can you improve accuracy when sizing? Here are some things to think about:
1. Have you considered the differences when sizing motor loads versus static loads? Motor loads have higher starting requirements (inrush); if inrush is not accounted for properly, a genset can fail to start.
2. Has the sizing calculation provided a full accounting for transient response? For example does it calculate genset:
· frequency dip
· voltage dip
· recovery time
It's important that the sizing accounts for more than just the alternator-caused voltage dip, but for the engine-related, or frequency-induced, voltage dip as well. Otherwise, predicted voltage dips can be half as much as actual.
3. Can the sizing calculation account for the lower genset frequency dip that results from an increase to the genset's adjustable voltage regulator setting?
It's important to know if and when this volts/hertz optimization can help size a smaller genset.
What are your experiences with sizing... and are there any tools or tips that you would like to share? Please post below.
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