The Math of Generators

Jim Siffring, Product Manager – Generators

Sales Meeting, January 2014

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The Math of Generators

ElectricalFormulas

Temperature

Zekes Reversible:

DegF – 32 / 9 * 5

DegC / 5 * 9 + 32

Distance

Temperature vs. Altitude Derate table

Self-excited

-180% overload capability

-Covers most applications

Generator Excitation

SELF-EXCITED

AREP

- 300% overload capability

- Motor starting

AREP

300A starting current 300 / 3 100A

Self excited

300A starting current 300 / 1,8 167A

Sizing Tricks

Look for electrical bill from utilityRead the demand rate.

Look at the KVA of transformer feeding site/service

Count up loads in amps, note working voltage

2-3x hp = KW

Motor loads

Motor StarterAcross The Line (ATL) or Direct On line (DOL) x 5-7 FLASoft Starters x 2.0 – 3.5 FLA

Wye DeltaReduced voltage electronic

Variable Frequency Drive (VFD) or Variable Speed Drive (VSD) x 2 – 3 FLA

Amps = Amperes = A = IFLA = Full Load Amps – off motor data tag

Voltage = V = E (normal folks) = U (Europe)

Motor starting problem

What generator will we use?

Voltage?Amperage?Starting method?

Site AltitudeAmbient TemperatureWhat kind of generator excitation?

What generator to use?

Committed to sustainable productivity.