Test equipment safety question: isolation transformer options?

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audiotubes

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Test equipment safety question: isolation transformer options?

« on: November 25, , 09:34:30 pm » I saw Dave's how not to blow up your scope video and other similar videos.

I started looking around for isolation transformers and the ones I saw are all two wire for the DUT. How can you test a device that has a 3 prong plug?

Also, isn't it possible to make an isolation transformer just by using a 1:1 transformer? I don't understand the high prices on the few units I saw.

Thank you. I have taken apart more gear than many people. But I have put less gear back together than most people. So there is still room for improvement.

Jwillis

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Re: Test equipment safety question: isolation transformer options?

« Reply #1 on: November 25, , 09:55:12 pm » The point of an Isolation transformer is to remove the earth ground so the test device or devices float separate from each other. There is no direct link between them. By adding earth ground connection they are no longer separate (isolated).
This is a very good video on the subject of isolation transformers with experimentation.Its a detailed explanation on the types and purpose.
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audiotubes

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Re: Test equipment safety question: isolation transformer options?

« Reply #2 on: November 25, , 10:17:18 pm » Thanks, I'll look at that video tomorrow.

Can devices designed for three wire power run normally without the ground connected? I have taken apart more gear than many people. But I have put less gear back together than most people. So there is still room for improvement.

coppercone2

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Re: Test equipment safety question: isolation transformer options?

« Reply #3 on: November 25, , 10:21:56 pm » you should make sure you have a device that needs it before you use it. With alot of test equipment you can just probe to the chassis for repairs. It usually is good enough to figure out what is wrong. at least that is my experience I have yet to use one. The following users thanked this post: audiotubes

theHWcave

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Re: Test equipment safety question: isolation transformer options?

« Reply #4 on: November 26, , 12:14:48 am » I put an isolation transformer in my lab https://youtu.be/HdTagUVHR8s. I technically didn't "built" the transformer, instead I bought it, I just put it into an enclosure and wired it up. Yes, they are expensive but sometimes you can find a bargain as I did. Also look on eBay for used ones, especially those yellow boxes with isolation transformers mainly  for building sites but make sure its really an isolation transformer with separated primary and secondary windings. Sometimes they sell transformers with just a single winding to get 2x115V out of 230V. You can't used those.  Next, you need to be clear how many watts you need, the price climbs steeply the more power is needed.  Normally I hang the DUT on the isolation transformer and leave the scope on normal mains (and grounded). This is safer because you usually touch the scope buttons and sockets way more than those of the DUT. Also it allows connecting USB cables/network cables to your scope which you can't if you hang it on an isolation transformer. However, if your DUT draws kilowatts, you may have no viable alternative and run it directly from mains and isolate the scope with its <100W instead.

BTW, in a crunch and not as a permanent solution, you can use two normal isolation transformers back to back, say 230Vin 12V out, connect the 12V to another transformer's 12V and you get 230V out on its primary, doubly isolated but there are some losses and of course the 12V need to be beefy, for 100W output the 12V better be able to support 10A on both transformers.

Lastly, even with isolation transformer, there are still plenty of ways to blow up the scope. My favourite one is forgetting that the 2nd, 3rd ... channel all use the same common as the 1st channel. Makes for some spectacular shorts.

To be honest, these days I am using my isolation transformer a lot less since having a 2nd battery powered scope is nowadays quite affordable and a true alternative for an isolation transformer (I am using an OWON HDS272 but there are plenty of similar ones. Something you may want to consider. Just make sure the USB cable to the charger/PC is NOT connected to the scope while measuring...
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themadhippy

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Re: Test equipment safety question: isolation transformer options?

« Reply #5 on: November 26, , 12:45:02 am » Quote

Also look on eBay for used ones, especially those yellow boxes with isolation transformers mainly  for building sites but make sure its really an isolation transformer with separated primary and secondary windings

yellow ones tend to be 240v in 110v output so not much use for a 1:1 isolation transformer unless you use 2 back to back The following users thanked this post: audiotubes

audiotubes

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Re: Test equipment safety question: isolation transformer options?

« Reply #6 on: November 26, , 06:43:47 am »

This is safer because you usually touch the scope buttons and sockets way more than those of the DUT. Also it allows connecting USB cables/network cables to your scope which you can't if you hang it on an isolation transformer. However, if your DUT draws kilowatts, you may have no viable alternative and run it directly from mains and isolate the scope with its <100W instead.

Great point, thanks

To be honest, these days I am using my isolation transformer a lot less since having a 2nd battery powered scope is nowadays quite affordable and a true alternative for an isolation transformer (I am using an OWON HDS272 but there are plenty of similar ones. Something you may want to consider. Just make sure the USB cable to the charger/PC is NOT connected to the scope while measuring...

I didn't even think about that. It's a good suggestion since I don't do much general A/C device repair. I'll look into that.

I want to look into fixing an air fryer that failed. It now shorts the mains after working ok a small number of times. It's a good excuse to buy a new gadget or two  I have taken apart more gear than many people. But I have put less gear back together than most people. So there is still room for improvement.

coppercone2

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Re: Test equipment safety question: isolation transformer options?

« Reply #7 on: November 26, , 08:15:07 am » just FYI if you are SURE chassis is earth and the frequency and precision is not high, you really should just use chassis.

and you can make a good ground point for the probe with this
https://www.pomonaelectronics.com/products/hardware/banana-jack-6-spade-lug. Just screw it under something and keep the ground hooked up into it. or a big ass alligator clip

Like so long you are sure you got ground I don't see the damn point. I almost consider my isolation transformer a waste of money. I like building the wooden boxes for it out of scrap cabinets though.

get a GFCI outlet instead. « Last Edit: November 26, , 08:23:45 am by coppercone2 »

The Residential Transformer is essential for safely delivering electricity to homes and businesses. They convert high-voltage power from the grid into usable low-voltage electricity. Understanding transformer types, costs, and installation requirements is crucial for making informed decisions in residential and industrial applications.

Figure 1-1 residential transformer diagram

The Basics About Residentialgreen boxTransformer

Figure 1-2 green box transformer

Have you discovered what the little green electrical box in yard your home is?

Figure 1-3 green transformer box/transformer box

what is the small green box outside my house? The residential transformer box outside your home transformer is usually a green residential Pad-Mounted Transformer for house, which is responsible for converting high-voltage electricity into low-voltage electricity for home use, providing power to a residential neighborhood or small commercial building. The electrical transformer residential’s green enclosure is designed to blend in with the environment while protecting the equipment inside from weather and external damage. Mostly found in green neighborhoods powered by underground cables, these residential electrical transformers types offer high safety, low noise levels, and easy maintenance.The electric transformer box making them an important part of modern residential power systems.

Do you know what’s at stake in thepower transformer box?

Figure 1-4 are green electrical boxes dangerous/electrical transformer box

Are green electric boxes dangerous ?The electrical transformer box is a common electrical equipment in our daily life, but electricity box outside also has certain safety hazards. If green electrical transformer box is not operated properly or if there is equipment failure, the big green electrical box may cause problems such as high-voltage electric shock, short circuit or fire. In addition, children or small animals accidentally touching an green electrical box can also pose a danger. Although the electromagnetic radiation generated by electric boxes outside is usually within the safe range, the transformers box should keep a proper distance from them. To ensure safety, transformer tone box should not be approached or opened at will during normal times.The small green electrical box in yard should be inspected and maintained regularly by professionals.

Did you know that green electrical boxes outside can just be moved around?

Figure1-5 Transformergreen electric box

The green electrical box is an important part of the electrical housing system and is usually responsible for converting high voltage electricity into household transformer electricity. transformer electrical box’s location is carefully designed to meet power distribution needs, as well as safety and ease of maintenance. Therefore, these electrical transformer power box outside house cannot normally be moved at will. If they do need to be repositioned, they must be assessed and operated by a professional power company to ensure the safety and proper operation of the power system.

Types and characteristics of residential transformers for electricity

Do you know what types of residential electrical transformers are available?

PadMounted Transformer/Residential Pad Mounted Transformer

What is a pad mounted transformer? A pad mounted transformer for tv is a ground-mounted electrical transformer, pad mounted transformers for electricity are primarily used to convert high voltage power (typically 7.2 kV to 35 kV) to low voltage power (e.g., 240/120 V) suitable for use in residential or small commercial installations. Pad mounted transformers are typically designed as a rugged metal pad mounted transformer boxes with anti-theft locks and high voltage warning signs to protect the pad-mounted transformer’s internal equipment from the environmental elements and outside damage. The 3 phase pad mountedtransformer box in yard is widely used.

3 phase pad mounted transformers are widely used for power distribution in underground transformer cable systems because pad-mounted transformers do not need to be supported by utility poles, three phase pad mounted transformers are clean looking and easy to maintain, and pad-mounted transformers are well suited for urban areas. Small transformers are ideal for urban neighborhoods and public areas that require an aesthetically pleasing design.

Pad mounted transformer building concrete pad first energy installations must adhere to strict guidelines to ensure safety and durability.A properly designed transformer mounting pad is crucial to ensure the stability and safety of the live front transformer installation.

Figure2-1 pad mounted transformer diagram/pad-mounted transformer diagram

Pad Mounted Transformer Dimensions

25 kva pad mounted transformer50 kva pad mount transformer75 kva pad mount transformer100 kva pad mount transformer150 kva pad mount transformer167 kva pad mount transformer300 kva pad mount transformer500 kva pad mount transformer750 kva pad mounted transformer kva pad mount transformer kva pad mounted transformer kva pad mount transformer

pad mounted transformer sizes

Figure 2-2 green electric box in yard

Pole Mounted Transformer/Pole Mount Transformer

A pole mounted transformer is an electrical transformer mounted on a utility pole. pole mounted transformers are typically used to convert high voltage (e.g., 7.2 kV or 12.47 kV) to low voltage (e.g., 240/120 V), 3 phase pole mounted transformers electronic and single phase pole mounted transformers are used to power homes, farms, and small commercial facilities. transformers and single phase pole mounted transformers are used to green electrical supply power to homes, farms and small commercial facilities. pole mounted distribution transformers have a compact design that saves space on the ground, making them suitable for use in rural, remote or space-constrained locations. Pole Mounted Distribution Transformers

Pole mounted transformers are directly connected to the overhead cables of the power grid by hanging them from poles. This type of installation facilitates easy access while avoiding the risk of flooding or physical damage to which ground-based transformers may be exposed. They typically provide power in single-phase or three-phase configurations, with flexible options depending on regional needs and load capacity.

Figure 2-3 pole mounted transformer diagram

Common pole mounted transformer specifications

10 kva pole mounted transformer15 kva pole mounted transformer25 kva pole mounted transformer37.5 kva pole mounted transformer50 kva pole mounted transformer75 kva pole mounted transformer100 kva pole mounted transformer150 kva pole mounted transformer167 kva pole mounted transformer200 kva pole mounted transformer250 kva pole mounted transformer500 kva pole mounted transformer

Figure 2-4 residential transformer box

Do you know what the characteristics of residential transformers are?

Figure2-5 what’s a transformer

The main feature of residential transformers is to convert high voltage electricity into low voltage electricity for household use, ensuring stable and reliable power supply. Depending on the installation environment, it can be a ground-mounted pad-type transformer suitable for urban residential areas, or a pole-type transformer, which is common in rural and remote areas. They are compact in design, energy-efficient, and meet international energy-saving standards. They are also equipped with sturdy casing and safety devices, and are durable and can usually be used for more than 20 years. These transformers not only ensure the safety of household electricity use, but also have the advantages of environmental protection and energy saving.

The transformer combo includes a power transformer and a circuit breaker in a compact unit for industrial applications.

What are the common voltage specifications for residential transformer?

Figure 2-6  transformer electrical box

In Western countries, the voltage specifications of house transformer is designed to meet the power needs of households and small communities. The input voltage typically ranges from 7.2 kV, 12.47 kV, 14.4 kV, to 24.94 kV. The transformer house seamlessly integrating with the power distribution system. The output voltage is standardized at 240/120 V, which is the widely adopted dual-phase power supply system. This voltage configuration ensures efficient operation of high-power devices such as heat pumps and air conditioners while providing stable power for low-power equipment like lighting and transformer on house appliances. This design not only optimizes power supply efficiency but also aligns perfectly with the power standards used across Western regions.

What is a residential transformer diagram?

Figure2-7 what is a transformers？-house transformer

What does a transformer look like？ A residential transformer diagram is a simplified illustration. The pad mounted residential transformer visually represents the internal structure, key components, and wiring connections of a residential transformer for electricity. It typically includes details such as the primary winding (connected to the high-voltage input), the secondary winding (providing low-voltage output like 240/120 V), the core (for electromagnetic conversion), and the grounding system (for safety). These diagrams are commonly used to explain the transformer’s working principle, guide installation, or assist in troubleshooting. They are valuable for both professionals and users to understand how the transformer functions and interacts with the electrical distribution system.

Technical Specifications of Residential Transformers

What is the typical size of a residential transformer?

Figure 3-1 residential transformer box/ transformer box electrical

The size of a residential transformer depends largely on its capacity and installation type. The capacity typically ranges from 15 kVA to 167 kVA, and the dimensions vary by installation type. Pad-mounted transformers are larger, generally measuring 1.2 m × 0.9 m × 1 m, and are suitable for ground installation in urban communities. Pole-mounted transformers are more compact, with a diameter of 60-80 cm and a height of around 1 m, making them ideal for mounting on poles in rural or remote areas.

How is a residential transformer wired?

Figure 3-2 green truck transformer

The wiring of a residential transformer must strictly follow electrical regulations. The high-voltage side typically receives an input voltage of 7.2 kV or 12.47 kV, connected to the power distribution grid. The low-voltage side provides a standard output voltage of 240/120 V, utilizing a dual-phase power supply system to meet household equipment needs. Additionally, a grounding system is essential, connecting the transformer casing to the distribution system’s ground network to ensure safety and prevent electrical leakage. All wiring must be performed by licensed electricians and comply with local electrical standards.

How much does a residential transformer cost?

Figure 3-3 how much does a residential transformer cost

How much do transformers cost? The cost of a residential electrical box transformer includes both equipment and installation expenses. Pad-mounted transformers typically cost between $2,000 and $8,000, with installation costs ranging from $1,500 to $3,000. Pole-mounted transformers are more economical, with equipment costs ranging from $1,000 to $4,000, and installation costs typically between $500 and $1,500. Additionally, annual maintenance costs are approximately $200 to $500, depending on the operating environment.

What is the lifespan of a residential transformer?

Figure 3-4 what is transformer electrical

The designed lifespan of a residential transformer is typically 20 to 30 years, though its actual service life can be influenced by several factors. Proper load usage, favorable environmental conditions, and regular maintenance can significantly extend its life. High-quality modern transformers, when well-maintained, can even last over 40 years. Regular inspections of wiring, cleaning of the casing, and replacement of aging components are critical to ensuring longevity.

Safety of Residential Transformers

How to read a residential transformer nameplate?

Figure 4-1 types of utility boxes in yard

The nameplate of a residential transformer is a metal or plastic label usually mounted on the transformer’s casing, providing key information about the equipment. Common details include the transformer capacity (kVA), input voltage, output voltage, frequency (Hz), phase type (single-phase or three-phase), efficiency rating, and manufacturer information. When reading the nameplate, special attention should be given to the voltage and capacity to ensure the transformer matches the electrical requirements. Additionally, the nameplate may include safety warnings and installation specifications, making it an essential reference for understanding the transformer’s performance and usage guidelines.

pole mounted transformer nameplate

Are residential transformers safe?

Figure 4-2 power box green

Residential transformers are designed and tested to meet stringent safety standards, making them very safe under normal operating conditions. Their casing is made of durable metal, offering waterproof, fireproof, and corrosion-resistant properties. Additionally, they are equipped with anti-theft locks and high-voltage warning signs to prevent unauthorized access. Grounding systems are also in place to effectively protect against electrical leaks and shocks. However, for safety reasons, it is advised not to approach or attempt to open a transformer. All maintenance and servicing should be carried out by licensed professionals.

How far should a transformer be from a house?

Figure 4-3 small transformers electrical

Does transformer need working space clearance in front? The distance between a transformer and a house is typically determined based on safety and maintenance requirements. Generally, a residential transformer should be placed at least 3 meters (approximately 10 feet) away from buildings. This ensures safety by reducing risks of electrical shock or fire and allows for proper heat dissipation and maintenance access. Depending on local regulations or utility company guidelines, this distance may vary, so it is essential to follow specific requirements during installation to comply with safety standards.

Weight and Selection Guide for Residential Transformers

Typical Weight Specifications of Residential Transformers

Figure 5-1 residential transformer box

The weight of a residential transformer green power box varies by type and capacity. Pad-mounted transformers home typically weigh between 200 kg and kg, with larger models exceeding 2 tons, making them suitable for ground installation. Pole-mounted transformers are more compact, weighing between 50 kg and 400 kg, ideal for pole installations. The exact weight depends on the transformer’s design, materials, and manufacturer, and professional equipment and personnel are required for transportation and installation.

How to Choose a Residential Transformer Supplier

Figure 5-2 green electric transformer box

When selecting a residential transformer supplier, consider factors like product quality, technical support, brand reputation, and after-sales service. Reliable electrical transformer suppliers should offer high-quality transformers that meet international standards (e.g., IEC, ANSI, DOE) and provide customization options to suit specific requirements. Comprehensive technical support and robust green box electrical transformers for sale services ensure smooth installation and operation. Additionally, assess the supplier’s market reputation and value for money to avoid potential issues and achieve long-term cost efficiency. The company transported the industrial electrical transformer on RGN trailers to ensure safe and efficient delivery to the power station construction site.

Shinenergy Can Provide Customized Residential Transformer Specifications

Single phase pole mounted transformer

Figure 6-1 power box green

The single-phase pole-mounted transformer serves as a distribution transformer in decentralized power electrical transformer supply networks, offering several advantages:

High Efficiency and Energy Saving:

• Designed with a high-efficiency, energy-saving wound core structure.
• Reduces low-voltage distribution line losses by over 99%.

Convenient Installation:

• Pole-type suspension installation, small volume, and low capital investment.
• Short low-voltage power supply radius.

High Reliability:

• Fully sealed structure with strong overload capability.
• High reliability in continuous operation.

Technical Data For Single-Phase Pole Mounted Distribution Transformer

Technical Data For Single-Phase Pole Mounted Distribution Transformer

Capacity(KVA)HighVoltage(V)TappingRangesLowVoltage(v)Loss (W)Dimension(mm)DOE EfficiencyNo-load Loss      （W）On-oad Loss           (W)WDH

±2*2.5%

110

120

208

240

277

347

415

416

480

600

690

60

80

100

120

130

150

330

370

450

620

850

520

560

610

635

754

770

795

Goto Haoshuo to know more.

565

590

625

975

840

965

890

905

935

935

98...599........49

Single Phase Pad Mounted Transformer

Figure 6-2 electrical transformer residential

Our single-phase pad-mounted transformer features an easy-to-open clamshell cabinet for quick and unobstructed access. This versatile design supports various protection and switching configurations.

Easy Maintenance:

• Clamshell cabinet for fast and easy maintenance.
• Unrestricted access to all connections.

Versatile Design:

• Supports multiple protection and switching configurations.
• Offers various service options.

High Reliability and Safety:

• Meets all reliability and safety standards.
• Ensures stable long-term operation.

Customizable Options:

• Available in various ratings.
• Advanced configurations to meet specific needs.

SPECIFICATION OF 10KVA TO 167KVA

SPECIFICATION OF 10KVA TO 167KVACapacity(KVA)HighVoltage(V)TappingRangesLowVoltage(v)Loss (W)Dimension(mm)DOE EfficiencyNo-load Loss      （W）On-oad Loss           (W)WDH

110

120

208

240

277

347

415

416

480

600

690

60

80

100

120

130

150

330

370

450

620

850

610

740

740

760

810

960

940

...599........49

Three phase pad mounted transformer

Figure 6-3 how long does it take to replace a residential transformer

Standard Compliance:

• Meets ANSI and DOE standards.
• Designed for usual service conditions per IEEE C57.12.00.

High Performance Design:

• Ratings available from 30 kVA to kVA.
• Primary voltages range from 2.4 kV to 35 kV (150 kV BIL).
• Secondary voltages up to 600 volts.

Versatile Configurations:

• All standard tap configurations available.
• Dual voltage available in most combinations.
• Dual voltage with taps only (series connection only).
• Impedance and loss options available in most designs.

TECHNICAL SPECIFICATION

TECHNICAL SPECIFICATIONRated capacity(KVA)VOLTAGE COMBINEDVector-groupNo-load Loss(W)Load Loss at 85°C(W)Impedance(%)Effiency(%)High Voltage(V)Tapping RangesLow Voltage(V)

±2*2.5%110

120

208

240

277

347

415

416

480

600

690

YNyn0Dyn.0-6.399..........

FQA

How long does it take to replace a residential transformer?

It typically takes 4 to 8 hours to replace a residential transformer green box in yard, depending on factors like location, accessibility, and weather conditions.

How does a residential transformer work?

A residential transformer works by stepping down high-voltage electricity from the power grid (e.g., 7.2 kV or 12.47 kV) to low-voltage electricity (240/120 V) suitable for household use. It uses electromagnetic induction, where the primary winding receives high voltage, and the secondary winding outputs low voltage. This ensures safe and efficient power delivery to homes.

What are clearances for 75 kVA transformer?

the minimum safety and operational distances required when installing a 75 kVA transformer. These clearances ensure safe operation, proper ventilation, and accessibility for maintenance. Safety clearances are typically defined by standards such as the NEC (National Electrical Code) or IEC, and they include space for electrical safety to prevent arcing or overheating, adequate airflow for cooling, and enough room for technicians to perform inspections and repairs. Following these requirements minimizes risks and ensures compliance with regulatory standards.

Where can I find a 24vdc transformer no e j0 near me?

You can search for the 24vdc transformer no e j0 at local electrical supply stores, online retailers, or nearby industrial equipment distributors. Ensure to verify the product specifications and availability with the supplier to match your requirements.House transformers I installed last month have significantly improved the power stability in the neighborhood. The Siemens 3 phase power transformer price is competitive.There are 5 green boxes placed neatly along the side of the road.

Where can I find a kVA transformer with 208/120 V output and reliable service in Downers Grove, IL?

If you’re looking for a kVA transformer Downers Grove IL, options are available to meet your industrial or commercial needs. For applications requiring kva transformer downers grove il 208/120 V output, electricity transformer can be sourced to match your electrical requirements. Additionally, reliable transformer electric service downers grove ensures professional installation, maintenance, and repair for all your name of green transformer truck systems.

what is a transformer electricity

Who is responsible for green cable boxes？

Green cable boxes are typically the responsibility of the local utility or telecommunication company that owns them. They manage installation, maintenance, and repairs. For issues, contact the company listed on the box or your local service provider.

green cable box outside

How much does a transformer cost?

The cost of a transformer varies by type and capacity.Residential pad-mounted transformers cost $2,000 to $8,000.Pole-mounted transformers range from $1,000 to $4,000.Industrial transformers can cost $10,000 to over $100,000.Small specialty transformers cost $50 to $500.Installation and maintenance add to the total cost.

For more information, please visit transformer testing equipment.