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Class 2 transformers are small line-frequency transformers that are widely used for control systems that require 24 VAC signaling, including residential and commercial HVAC systems, industrial control systems, doorbells, and much more. In this work, we sampled and tested seven Class 2 transformers, each across different operating conditions, in order to characterize their efficiencies and note their shortcomings. We also provide possible improvements and solutions. We see on average a peak efficiency of 84.43% with 5.37 W of power loss when operated at 75% (30 VA output power) of their rated power, a 1.84% efficiency drop from the temperature rise that occurs at steady state when operated with full load, 2.8 W of no-load loss at 120 VAC input, and a no-load loss contribution of over 50% when operating at less than 75% load power. With these values, there is a clear goal to strive for in order to improve or create an alternative to these Class 2 transformers.
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Low-Power Solid-State Transformers to Replace Line-Frequency Class 2 Transformers
Class 2 transformers are small line-frequency transformers widely used for control systems requiring 24 VAC signaling, including residential and commercial HVAC systems, industrial controls, and much more. These transformers have large standby losses, low efficiencies, large weights, and high costs. In this work, we propose a power electronic alternative in the form of a low-power solid-state transformer. We design and test two 40 VA 120 VAC to 24 VAC solid state transformers, including a two-stage and a single-stage topology. Both converters provide higher efficiencies across all load ranges compared to the Class 2 line-frequency transformers, especially at light load (5 VA) with improvements of 19.6% and 29.9%, respectively. Standby losses for the two are 417 mW and 196 mW, compared to an average of 2.8 W standby loss for 40 VA Class 2 line-frequency transformers.
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- PAR ID:
- 10531573
- Publisher / Repository:
- IEEE
- Date Published:
- ISSN:
- 2470-6647
- ISBN:
- 979-8-3503-1664-3
- Page Range / eLocation ID:
- 3163 to 3170
- Subject(s) / Keyword(s):
- Solid-state Transformer standby power class 2 transformer
- Format(s):
- Medium: X
- Location:
- Long Beach, CA, USA
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/APEC48139.2024.10509077
