Have you ever thought about the system that keeps control panels, lighting systems, and instrumentation working well in huge electrical environments? The solution is auxiliary transformers. Even though they are small, they play a huge role in running important support systems. They make sure that the work behind the scenes at substations and industrial plants is done effectively and safely. However, an incorrect size or selection can result in your HVAC system losing energy, failing, or having to shut down, which might be expensive.
In this blog, we’ll explore the selection and sizing of auxiliary transformers from an electrical engineer’s point of view.
Auxiliary Transformers: The Backbone of Modern Electrical Systems
Why Auxiliary Transformers Are Indispensable in Power Distribution Networks
Using auxiliary transformers, the main voltages can be decreased to the right voltages needed by the loads. Mainly, power transformers carry large amounts of electricity, whereas auxiliary transformers supply the power needed for all the auxiliary units in the plant.
Auto transformer starters are used with them to better handle the load surge that occurs during a motor start. Line chokes help to limit harmonic distortion and make the system more stable.
Where Auxiliary Transformers Are Used Across Industries
Auxiliary transformers can be found in all sorts of industries, whether in power stations, production plants, oil & gas areas, or solar farms. They are commonly put to use with main transformers to get proper energy metering and protection. Because they are flexible, they are well suited to holding things like lighting, HVAC equipment, control panels, and relay protection circuits.
Sizing Matters: How to Calculate Auxiliary Transformer kVA Rating
A Practical Approach to Transformer Sizing
Getting the size right is the first important process in choosing the proper transformer. Formula for kVA rating.
- For 3-phase:
kVA = (Voltage × Current to evaluate× √3) / 1000 - For 1-phase:
kVA = (Voltage × Current) / 1000
For example, if your control panel load is 20 A at 415 V, the kVA required is
143.7 kVA is equal to (415 × 20 × √3)/1000.
Understanding Load Groups: Essential vs. Non-Essential
In evaluating the load that needs to be supported, you must distinguish critical devices from non-critical ones. Since control room equipment is used all the time, it calls for stronger protection. In this step, engineers certainly get the proper size and enhance the design by focusing on the auxiliary transformer voltage levels and current ratings.
Critical Factors to Consider When Selecting Auxiliary Transformers
Matching Input and Output Voltages
An auxiliary transformer has to be connected to the main voltage (for example, 11 kV or 6.6 kV) and give the right secondary voltage (often 400 V or 415 V). It means all the devices operating together remain functional.
Efficiency and Load Regulation Under Varying Conditions
It is necessary for transformers to perform well at their specified and reduced capacity loads. Make sure to notice any issues with copper and iron, as they influence both expenses and how much energy the plant uses. A system with lower voltage drops is well regulated.
Installation Environment and Cooling Types
The room’s temperature, the level of humidity, dust, and available air space are all very important. Dry-type transformers are commonly installed wherever it is unsafe to use oil or in indoor areas. Some types have oil in them and could be preferred for bigger, outdoor power setups.
Integrated Operation with Auto Transformer Starter and Line Chokes
Auxiliary transformers provide the power needed for the auto transformer starter that starts motors at safe voltages. Also, using line chokes on the input of a transformer cuts electrical noise and boosts its power factor, improving both the equipment’s steady performance and life expectancy.
Auxiliary Transformer Ratings Explained
Primary and Secondary Ratings
Being aware of each auxiliary transformer’s voltage levels and current ratings is very important. The most common configurations are 6.6 kV/400 V or 11 kV/433 V. The current capacity must be high enough to carry all the needed load and also be safe. If the air conditioner is too small, the equipment can overheat, but if it is too large, you must pay more for the system without any gain.
Why Current Transformers Are a Must-Have in Modern Systems
Protection and proper monitoring of energy are made possible by using Current Transformers (CTs). Thanks to the auxiliary transformers, CTs detect problems and help interrupt the electricity supply, as well as keep track of how electricity is being used in the system. Pick the right levels of accuracy and burden-carrying capacity for the protective relays and metering systems.
Control and Protection: Keeping Auxiliary Transformers Safe and Smart
Protection Devices That Keep Your System Secure
Usually, fuse disconnects, overload relays, Buchholz relays (for oil-filled designs), and thermal cutoffs are included in protective schemes. They make sure that defects or overloads on either the primary or secondary side are stopped from reaching the transformer.
Smarter Control and Remote Monitoring Capabilities
Some advanced control features are manual and automatic modes, connecting to PLCs, and watching the system remotely with SCADA. Because of these systems, there are more accurate fault detections, less downtime experienced, and the auxiliary transformer protection and control schemes work smoothly.
Best Practices for Auxiliary Transformer Installation:
Pre-Installation Checks and Environmental Readiness
Put the transformer on a flat and stable base, allow enough clearance between it and obstacles, and provide enough ventilation, which is very important in dry-type transformers. Ensure your critical hardware meets national standards such as IS/IEC codes to avoid risk and make it safe.
Mechanical and Electrical Installation Guidelines
It is extremely important to do proper earthing, cable lugging, and phase sequencing. When using auto transformer starters, line chokes, and current transformers, protection coordination needs extra attention.
Commissioning with a Detailed Testing Checklist
Before starting up, make sure to do insulation resistance tests, check the polarity and phase, and look at the vector groups of the transformer. These steps guarantee that the system can work properly and safely after being started up.
Choose Wisely, Operate Safely, and Plan Ahead
Matching voltage levels isn’t the only aspect to consider; you should understand the demands and safety needs of the circuit and how the transformer will be integrated. When everything is sized properly with your starters, line chokes, and current transformers, your system will be dependable and efficient for longer.
If you want reliable auxiliary transformers for your industry, you should partner with Trio Transformers. We’re the best provider of world-class transformers tailored to your specific requirements.
