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Fix ZeroDivisionError in simple_efficiency when load_loss=0 #2646

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Fix ZeroDivisionError in simple_efficiency when load_loss=0 #2646

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c7c9151
Fix ZeroDivisionError in simple_efficiency when load_loss=0
aman-coder03 Dec 28, 2025
ba4b87b
Remove trailing whitespace in transformer
aman-coder03 Dec 28, 2025
b20e579
use numerically stable quadratic form in simple_efficiency
aman-coder03 Jan 2, 2026
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6 changes: 5 additions & 1 deletion pvlib/transformer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -105,13 +105,17 @@ def simple_efficiency(
pg. 101.
''' # noqa: E501

if load_loss == 0:
return input_power - no_load_loss * transformer_rating

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@cwhanse cwhanse Jan 2, 2026

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Suggested change
if load_loss == 0:
return input_power - no_load_loss * transformer_rating

I don't think this is necessary with the alternate form of the quadratic equation.

input_power_normalized = input_power / transformer_rating

a = load_loss
b = 1
c = no_load_loss - input_power_normalized

output_power_normalized = (-b + (b**2 - 4*a*c)**0.5) / (2 * a)
disc = (b*b - 4*a*c)**0.5
output_power_normalized = 2*c / (-b - disc)

output_power = output_power_normalized * transformer_rating
return output_power