Padmount Transformer Full Load Amps Chart: Complete FLA Reference

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Comprehensive full load amperage chart for dead-front padmount transformers. Find FLA values for all standard kVA
ratings at common voltages, plus wire sizing recommendations.

⚡ FLA Calculation Formulas

Single-Phase:
FLA = (kVA × 1000) ÷ Voltage		Three-Phase:
FLA = (kVA × 1000) ÷ (Voltage × √3)

Knowing the Full Load Amperage (FLA) of your padmount transformer is essential for proper
conductor sizing, circuit breaker selection, and protection coordination. This chart provides FLA
values at all common secondary voltages.

Single-Phase Padmount Transformer FLA Chart

Full load amperage for single-phase padmount transformers at common secondary voltages:

kVAFull Load Amps (FLA) by Secondary VoltageSpecs
120V208V240V277V480V
25 kVA208.3 A120.2 A104.2 A90.3 A52.1 AView
→
37.5 kVA312.5 A180.3 A156.3 A135.4 A78.1 AView
→
50 kVA416.7 A240.4 A208.3 A180.5 A104.2 AView
→
75 kVA625.0 A360.6 A312.5 A270.8 A156.3 AView
→
100 kVA833.3 A480.8 A416.7 A361.0 A208.3 AView
→
167 kVA1391.7 A803.0 A695.8 A602.9 A347.9 AView
→

Three-Phase Padmount Transformer FLA Chart

Full load amperage for three-phase padmount transformers. Note: Three-phase FLA is calculated using
the √3 (1.732) factor.

kVAFull Load Amps (FLA) by Secondary VoltageSpecs
208V240V277V480V
75 kVA208.2 A180.4 A156.4 A90.2 AView
→
112.5 kVA312.3 A270.6 A234.6 A135.3 AView
→
150 kVA416.4 A360.8 A312.8 A180.4 AView
→
225 kVA624.6 A541.3 A469.2 A270.6 AView
→
300 kVA832.8 A721.7 A625.6 A360.8 AView
→
500 kVA1388.0 A1202.8 A1042.6 A601.4 AView
→
750 kVA2082.0 A1804.2 A1564.0 A902.1 AView
→
1000 kVA2776.0 A2405.6 A2085.3 A1202.8 AView
→
1500 kVA4164.0 A3608.4 A3128.0 A1804.2 AView
→
2000 kVA5552.0 A4811.3 A4171.0 A2405.6 AView
→
2500 kVA6940.0 A6014.1 A5213.8 A3007.0 AView
→

Conductor Sizing Guide for Padmount Transformers

Proper conductor sizing is critical for safety and code compliance. Use this guide based on copper conductors with
75°C insulation per NEC Table 310.16.

Current RangeCopper ConductorTypical Application
0-20 A#12 AWGSmall branch circuits
21-30 A#10 AWGStandard branch circuits
31-50 A#8 – #6 AWGSub-panels, small equipment
51-100 A#4 – #1 AWGService entrance, panels
101-150 A1/0 – 2/0 AWGMain service, feeders
151-200 A3/0 – 4/0 AWGLarge feeders
201-300 A250-350 MCMCommercial service
301-500 A400-750 MCMIndustrial feeders
500+ AParallel conductorsLarge industrial loads
⚠️ Important: Always apply NEC derating factors for ambient temperature, conduit fill, and
continuous loads. Consult a licensed electrician for final sizing.

FLA Calculation Examples

Example 1: Single-Phase 50 kVA at 240V

FLA = (50 × 1000) ÷ 240 = 208.3 Amps
Recommended conductor: 4/0 AWG copper

Example 2: Three-Phase 300 kVA at 480V

FLA = (300 × 1000) ÷ (480 × 1.732) = 360.8 Amps
Recommended conductor: 500 MCM copper

Example 3: Three-Phase 1000 kVA at 208V

FLA = (1000 × 1000) ÷ (208 × 1.732) = 2776 Amps
Recommended: Multiple parallel 750 MCM conductors

Frequently Asked Questions

What is Full Load Amps (FLA)?

FLA is the current drawn by a transformer when it is delivering its rated kVA at its rated secondary voltage. It
represents the maximum continuous current the secondary conductors must carry.

How do I calculate FLA for a padmount transformer?

For single-phase: FLA = kVA × 1000 ÷ Voltage. For three-phase: FLA = kVA × 1000 ÷
(Voltage × 1.732).

What size breaker do I need?

The primary overcurrent protection is typically set at 125% of transformer FLA per NEC Article 450.
Secondary protection depends on impedance and load characteristics.

Related Resources

📊 More Reference Charts:

Standards & References

Disclaimer: FLA values are calculated at nameplate voltage. Actual current may vary based on voltage regulation
and load power factor. Wire sizing recommendations are guidelines only – always follow NEC requirements and
consult with a licensed electrical engineer. Last updated: January 2026

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