UL Autotransformers
Reviewed by: Jon Lowy, consulting engineer
Description
UL Autotransformers are electrical devices designed to convert electrical power in an AC system from one voltage level to another using a single continuous winding. This winding serves both as the primary and secondary coil, allowing for a compact and efficient design. The autotransformer is typically smaller, lighter, and cheaper than other types of transformers, making it a cost-effective solution for voltage conversion.
Working Principle
The working principle of an autotransformer involves both conduction and induction. Unlike traditional transformers with separate primary and secondary windings, an autotransformer has a single winding that is tapped at various points to provide different voltage levels. The direct electrical connection between the windings allows part of the energy to be transferred by conduction, while the magnetic coupling ensures energy transfer by induction. This design makes autotransformers more efficient and capable of delivering more power than a two-winding transformer of similar size.
Applications
Autotransformers are commonly used in low power applications where electrical isolation is not required. They are often employed to connect circuits with different voltage classes. Specific examples include their use in audio equipment to remove ground noise, and in variable voltage applications where a variac or variable autotransformer is used to provide adjustable output voltage.
Advantages over other Autotransformers
Compared to two-winding transformers, autotransformers are generally more cost-effective due to their simpler construction. They are also more efficient, delivering more power for a given size and weight. Additionally, autotransformers can be more compact, making them suitable for applications where space is limited.
Limitations
One significant limitation of autotransformers is the lack of electrical isolation between the input and output circuits. This can be a disadvantage in applications where isolation is necessary for safety or noise reduction. Additionally, autotransformers are typically not suitable for high power applications due to their design constraints.
Considerations
When considering the use of an autotransformer, it is important to evaluate the initial costs, which are generally lower than those of two-winding transformers. Operating expenses are also reduced due to higher efficiency. However, the lack of electrical isolation may impact durability and safety, requiring careful consideration of the specific application requirements. Maintenance costs may be lower due to the simpler design, but accuracy in voltage conversion should be assessed to ensure it meets the application's needs.
from Toroid Corp. of Maryland
Optional enclosure with or without cord, plug and receptacle [See More]
- Agency: CSA; UL
- Core Type: Toroidal Core
- Winding Turns: Step-Up Transformer
- Output Type: AC
from Hubbell Incorporated
DISTRIBUTION, DRY TYPE. 7.37 INCH. 19.25 INCH. 15.21 INCH. 50/60 HZ FREQUENCY RATING. 3 PHASE(S). UL, CSA APPROVAL. INDUSTRIAL, COMMERCIAL APPLICATION. NEMA 2 ENCLOSURE. 15/12 KVA POWER RATING. 600/480 VAC PRIMARY VOLTAGE. 480/380 VAC SECONDARY VOLTAGE. APPLICABLE STANDARD ANSI, OSHA. MOUNTING TYPE... [See More]
- Agency: CSA; UL
- Input Voltage: 480 to 600
- Operating Frequency: 50 to 60
- Output Voltage: 380 to 480
from Powertronix Inc.
3-Phase Auto Transformers offer a significant size and weight reduction as well as lower cost. Auto Transformers are for voltage step up or step down when there is no requirement for electrical isolation. APPLICATIONS. Automation. Marine [See More]
- Agency: RoHS; UL
- Type: Three Phase Transformers
- Mounting: Flange, Potted in a Craddle
- Power Rating (VA): 2000 to 120000
from Acme Electric Corp. / Power Distribution Products
Acme's single phase transformers are design for use in industrial and commercial application. Transformers rated up to 25 kVA are enclosed within an encapsulated, NEMA 3R enclosures. Standard transformers rated from 37.5 to 250 kVA are enclosed in ventilated, NEMA 2 enclosures (optional... [See More]
- Agency: ANSI; CSA; UL; CE and IEEE
- Cooling Method: Air
- Winding Turns: Step-Down Transformer
- Output Type: AC
from Block USA, Inc.
Rated input voltage 3 x 200/208 - 3 x 690 Vac. Rated output voltage 3 x 400 Vac. Rated power 2000 - 250000 VA. Insulation class F. Maximum ambient temperature 40 °C. Efficiency up to 98 %. Degree of protection IP 00/23/54. Optionally adapted package for higher degrees of protection. [See More]
- Agency: UL
- Input Voltage: 200 to 208
- Operating Frequency: 50 to 60
- Output Voltage: 400
from Standex-Meder Electronics
TA-TAE-FPT Series Auto power transformers are line frequency magnetics designed in an open, enclosed package with an economical method of changing voltage levels. These auto transformers are widely used to operate electrical equipment outside of North America. Typically 50% smaller than similar... [See More]
- Agency: CSA; UL
- Input Voltage: 115 to 230
- Output Type: AC
- Output Voltage: 115 to 230
from Mirus International, Inc.
A 3-phase, low zero sequence impedance autotransformer, which when connected near to and in parallel with the harmonic generating non-linear loads (usually connected at the distribution panel), provides an alternate path for 3rd, 9th, & 15th current harmonics (triplens) which the loads create. [See More]
- Agency: CSA; UL; CE
- Power Rating (VA): 750000
- Input Voltage: 600
from Hubbell Incorporated
DISTRIBUTION, DRY TYPE. 5.13 INCH. 5.5 INCH. 11.62 INCH. 60 HZ FREQUENCY RATING. 1 PHASE(S). UL, CSA APPROVAL. INDUSTRIAL, COMMERCIAL APPLICATION. NEMA 3R ENCLOSURE. 3 KVA POWER RATING. 240 VAC PRIMARY VOLTAGE. 120/240 VAC SECONDARY VOLTAGE. APPLICABLE STANDARD ANSI, OSHA. MOUNTING TYPE WALL. DESIGN... [See More]
- Agency: CSA; UL
- Input Voltage: 240
- Operating Frequency: 60
- Output Voltage: 120 to 240
from Powertronix Inc.
Auto Transformers are single winding toroidal transformers for voltage step up or step down, when there is no requirement for electrical isolation. Auto Transformers offer a significant size and weight reduction as well as lower cost. APPLICATIONS. Industrial Automation. Electrical Equipment [See More]
- Agency: RoHS; CSA; UL
- Core Type: Toroidal Core
- Winding Turns: Step-Up Transformer; Step-Down Transformer
- Mounting: Center Potted with Thru Hole, Flange, Excapsulated, Custom Mounting Bracket
from Acme Electric Corp. / Power Distribution Products
Acme ’s low voltage distribution transformers are designed for industrial and commercial applications. All of Acme ’s general purpose transformers are rated for 600 volts and below. Encapsulated units are offered in ratings up to 15kVA. Ventilated units are available in ratings up to... [See More]
- Agency: ANSI; CSA; UL; CE and IEEE
- Cooling Method: Air
- Winding Turns: Step-Down Transformer
- Output Type: AC
from Block USA, Inc.
Input rated voltage 3 x 690 Vac. Output rated voltage 3 x 400 Vac. Rated power 650 - 1386 VA. Ambient temperature +60 ° C. Protection index IP 00. Autotransformer. to: VDE 0570 Part 2-13, DIN EN 61558-2-13, EN 61558-2-13,. IEC 61558-2-13. Matching transformers to adjust the supply voltage of... [See More]
- Agency: UL
- Input Voltage: 690
- Operating Frequency: 50 to 60
- Output Voltage: 400
from Hubbell Incorporated
DISTRIBUTION, DRY TYPE. 19.4 INCH. 24.4 INCH. 25.5 INCH. 50/60 HZ FREQUENCY RATING. 3 PHASE(S). UL, CSA APPROVAL. INDUSTRIAL, COMMERCIAL APPLICATION. NEMA 3R ENCLOSURE. 112.5/90 KVA POWER RATING. 600/480 VAC PRIMARY VOLTAGE. 480/380 VAC SECONDARY VOLTAGE. APPLICABLE STANDARD ANSI, OSHA. MOUNTING... [See More]
- Agency: CSA; UL
- Input Voltage: 480 to 600
- Operating Frequency: 50 to 60
- Output Voltage: 380 to 480
from Block USA, Inc.
Rated input voltage 110/125/230/240 Vac. Rated output voltage 110/125/230/240 Vac. Rated power 150 - 3000 VA. Insulation class B or E. Maximum ambient temperature 40 °C. Degree of protection IP 00. Autotransformer. to: VDE 0570 Teil 2-13, DIN EN 61558-2-13, EN 61558-2-13, IEC 61558-2-13, UL... [See More]
- Agency: UL
- Input Voltage: 110 to 240
- Operating Frequency: 50 to 60
- Output Voltage: 110 to 240
from Hubbell Incorporated
DISTRIBUTION, DRY TYPE. 9.03 INCH. 20.3 INCH. 18.86 INCH. 50/60 HZ FREQUENCY RATING. 3 PHASE(S). UL, CSA APPROVAL. INDUSTRIAL, COMMERCIAL APPLICATION. NEMA 2 ENCLOSURE. 75/60 KVA POWER RATING. 600/480 VAC PRIMARY VOLTAGE. 480/380 VAC SECONDARY VOLTAGE. APPLICABLE STANDARD ANSI, OSHA. MOUNTING TYPE... [See More]
- Agency: CSA; UL
- Input Voltage: 480 to 600
- Operating Frequency: 50 to 60
- Output Voltage: 380 to 480