Basics of Low Voltage Distribution Transformers-Chapter 1 · Transformers come in a variety of...

Basics of Low Voltage Distribution TransformersA quickSTEP Online Course

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© Siemens Industry, Inc. 2017

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Siemens is a trademark of Siemens AG. Product names mentioned may be trademarks or registered trademarks of their respective companies.

National Electrical Code® and NEC® and NFPA 70® are registered trademarks of the National Fire Protection Association.

NEMA® is a registered trademark and service mark of the National Electrical Manufacturers Association.

UL® is a registered trademark of UL, LLC.

Other trademarks are the property of their respective owners.

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Course Topics

Welcome to Panelboards. This course covers the following topics:Chapter 1 - Introduction

• Overview• Transformer Basics

Chapter 2 – Transformer Information• Specifications and Ratings

Chapter 3 – Siemens Transformers• Transformer Types

Final ExamIf you do not have an understanding of basic electrical concepts, you should complete Basics of Electricity before attempting this course.

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Course Objectives

Upon completion of this course you will be able to…

• Describe the role of low voltage distribution transformers in an electrical distribution system.

• Describe how transformers work and the theories and concepts behind their design.• Identify important standards for low voltage distribution transformers• Describe the typical data found on a low voltage distribution transformer nameplate.• Describe various types of Siemens low voltage distribution transformers and the

appropriate applications for each type.

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SITRAIN® Training for Industry

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Utility Power Distribution

Power, originating at a power generating plant, is distributed to residential, commercial, and industrial customers through various transmission lines and substations.

The most efficient way to do this is to increase the voltage while at the same time reducing the current. This is necessary to minimize the energy lost in heat on the transmission lines. These losses are referred to as I2R (I-squared-R) losses because they are equal to the square of the current times the resistance of the power lines. Once the electrical energy gets near the end user, the utility steps down the voltage to the level needed by the user.

The device that utilities use to step up the voltage at the generator end and step down the voltage at the user end is called a transformer. Transformers are also used inside facilities to further reduce or increase the voltage to the level required by systems and devices.

This course is intended to cover the low voltage distribution transformers used by commercial and industrial facilities as part of their power distribution systems. Siemens also sells equipment to electrical utilities; however, utility transformers are not covered in this course. Page 1-6


Residential Power Distribution

Power distribution systems are used in every residential, commercial, and industrial building to safely control the distribution of electrical power throughout the facility.

Most of us are familiar with the power distribution system found in the average home. Power purchased from a utility company enters the house through a metering device. The power is then distributed from a load center to various branch circuits for lighting, appliances, and electrical outlets.

Because the voltage applied to the utility meter in a typical residential application has already been stepped down to 120/240 VAC, a level usable by many electrical devices, the roll that transformers play in residential applications is not obvious. However, many devices have transformers built-in to further step down the voltage where necessary.

This course does not cover these small, embedded transformers, but the principles of operation are the same as those that are covered.

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Commercial and Industrial Distribution

Power distribution systems used in commercial and industrial locations are often complex. They include metering devices to measure power consumption, main and branch disconnects, protective devices, switching devices to start and stop power flow, conductors, and transformers. Power may be distributed through various switchboards, transformers, and panelboards.

The primary role that low voltage distribution transformers play in commercial and industrial applications is essentially the same as in other applications, to transform voltage and current to the levels needed by the equipment employed.

For example, in the accompanying simplified illustration, transformers are used to reduce the voltage from 480 VAC to 120 VAC for lighting and office equipment use.

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Low Voltage Distribution Transformers

Transformers come in a variety of sizes and ratings. Most of transformers covered in this course are referred to as low voltage distribution transformers. Most of the transformers covered in this course are also referred to as dry-type transformers because they are not filled with any fluid.

These transformers are rated for 600 VAC and below and intended for supplying appliance, lighting, and power loads. Common supply voltages include: 600, 480, 277, 240, and 208 VAC.

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Chapter 1 – Introduction

This chapter covers the following topics:

• Overview

• Transformer Basics

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What is a Transformer?

Transformers are electromagnetic devices that transfer electrical energy from one circuit to another by mutual induction. As previously mentioned, they are frequently used to step a voltage or current up to a higher level or down to a lower level. They can also be used to limit electrical noise transfer or to match circuit impedances.

A single-phase transformer has two coils, a primary coil and a secondary coil. Energy is transferred from the primary to the secondary via mutual induction.

The accompanying illustration shows an AC source connected to the primary coil. The magnetic field produced by the primary induces a voltage in the secondary coil, which supplies power to a load.

Mutual inductance between two coils depends on their flux linkage. Maximum coupling occurs when all the lines of flux from the primary coil cut through the secondary coil. To maximize the amount of coupling, both coils are often wound on the same iron core, which provides a good path for the lines of flux. Keep in mind that the coils of wire are insulated from each other and from the core. The following discussions of transformers apply to transformers with a core made from iron or steel. Page 1-12


Basic Principles

Transformers operate on alternating current, rather than direct current. This is because it takes constantly varying current to allow the transformer to operate.

The alternating current applied to the transformer’s primary coil causes magnetic flux to flow in the core. This flux, in turn, induces an alternating current in the secondary coil.

Because this type of transformer has a core of iron, steel, or similar material, the magnetic flux is concentrated in the core. This allows virtually all the energy from the primary to be transferred to the secondary. Some energy is lost in heat in the conductors or core, but transformers are designed to minimize these losses.

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Transformer Turns Ratio

There is a relationship between primary and secondary voltage, current, and impedance and the ratio of transformer primary turns to secondary turns.

When the primary has fewer turns than the secondary, voltage is stepped up from primary to secondary. For the circuit on the left, the transformer secondary has twice as many turns as the primary, and voltage is stepped up from 120 VAC to 240 VAC. Because the impedance of the load is also higher than the impedance of the primary, current is stepped down from 10 amps to 5 amps.

When the primary has more turns than the secondary, voltage is stepped down from primary to secondary. For the circuit on the right, the primary coil has twice as many turns as the secondary coil, and voltage is stepped down from 240 VAC to 120 VAC. Because the impedance of the load is lower than the impedance of the primary, the secondary current is stepped up from 5 amps to 10 amps.

Transformers are rated for the amount of apparent power they can provide. Because values of apparent power are often large, the transformer rating is frequently given in kVA (kilovolt-amps).

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Step-up/Step-down Considerations

While it is technically true that a step-up or step-down transformer can be installed in reverse to provide the opposite functionality, before reversing a transformer, it is important to check the transformer’s ratings and make sure that they are not exceeded.

For example, if a transformer designed to operate with a 240 volt primary and a 120 volt secondary is reversed, it may not be able to handle the inrush current that occurs when power is applied to the primary.

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Autotransformers

Most transformers have primary coils and secondary coils that are electrically isolated from each other. This is often desirable to reduce the electrical noise transferred from primary to secondary and to block the flow of direct current.

Having primary and secondary coils that are electrically isolated from each other is not always necessary, however. Autotransformers are constructed with a single, continuous winding for each phase with both the input and output circuits connected to this winding. This design reduces cost.

Autotransformers typically have multiple taps so that the amount by which the voltage is stepped up or down can be adjusted.

Because autotransformers do not isolate the primary and secondary windings, they may not meet some local electrical codes.

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Three-Phase Power

Up till now, we have been talking only about single-phase AC power. Single-phase power is used where power demands are relatively small, such as for a typical home.

However, power companies generate and distribute three-phase power. Three-phase power is used in commercial and industrial applications.

Three-phase power, as shown in the accompanying illustration, is a continuous series of three overlapping AC cycles. Each wave represents a phase and is offset by 120 electrical degrees from each of the two other phases.

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Three-Phase Transformers

Transformers used with three-phase power have three interconnected coils in both the primary and the secondary. These transformers can be connected in either a wye or a delta configuration. The type of transformer and the actual voltage depend on the requirements of the power company and the needs of the customer.

The accompanying illustration shows the secondary of a wye-connected transformer and the secondary of a delta-connected transformer. These are only examples of possible distribution configurations, the specific voltages and configurations vary widely depending upon the application requirements.

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Buck-Boost Transformers

Buck-boost transformers are flexible single-phase or three-phase transformers designed for use in multiple configurations. Buck-boost transformers are manufactured and shipped as standard transformers with isolated primary and secondary windings, fixed input and output voltages, and a stated kVA rating.

Although their low-voltage and high-voltage windings are isolated before field connections are made, where local codes permit, these transformers can be connected as autotransformers, which do not provide primary to secondary isolation. Buck-boost transformers can be configured to buck (reduce) or boost (increase) voltage by a small amount (typically 5 to 20 percent). For example, a common application for a boost configuration is for use in a facility with a 208 VAC service that has motors or other equipment that operates on 240 VAC.

The accompanying illustration shows a few of the possible buck-boost transformer configurations. Keep in mind that autotransformers are not used in closed delta configurations because of their impact on power factor.

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Isolation Transformers

Standard transformers provide a degree of isolation by blocking the flow of direct current from the primary circuit to the secondary circuit.

For some applications, additional isolation is required. For example, a motor drive isolation transformer is often used to supply power to a variable speed drive. These transformers differ from standard transformers by the additional bracing placed on windings to withstand mechanical stress and overload conditions.

Some isolation transformers incorporate an internal electrostatic shield to reduce the flow of electrical noise and high-frequency disturbances between the primary and secondary circuits. An electrostatic shield is a copper foil between the primary and secondary windings that is grounded at installation. Siemens motor drive isolation transformers have an electrostatic shield option.

Siemens isolation and filtering transformers are designed to protect sensitive equipment from surges, spikes, and line noise. These transformers incorporate an internal electrostatic shield, surge protection on the primary side, and a low-pass filter on the secondary side.

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For the full course duration, you can complete assignments and reinforce classroom instruction using a virtual cloud-based application providing 24/7 access to fully functional Siemens software such as SIMATIC STEP 7 and PLCSIM.


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Chapter 2 – Transformer Information


• Specifications and Ratings

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Transformer Standards

Several organizations issue standards for transformer design, construction, installation, and performance. The following list includes some of these organizations.

Underwriters Laboratories, Inc. (UL) - Transformers bearing the Underwriters Laboratories listing mark must pass a series of performance tests. These tests and standards relate to the strength and integrity of a transformer when subjected to specific operating and environmental conditions. UL 1561 is a standard that covers general purpose and power transformers.

The National Electrical Manufacturers Association (NEMA) - NEMA standards for transformers are described in NEMA publication ST 20. All Siemens transformers are designed to meet or exceed these standards.

IEEE (formerly called the Institute of Electrical and Electronic Engineers) and the American National Standards Institute (ANSI) -These organizations provide standards for dry-type distribution and power transformers and autotransformers. These standards are described in ANSI/IEEE C57.12.01 and C57.12.91.

The National Fire Protection Association issues the National Electrical Code® , also referred to as the NEC ® or NFPA 70, which covers many aspects electrical systems. Page 2-2


Transformer Nameplate

Transformer ratings can be found on a nameplate that is typically attached to the transformer’s enclosure.

As shown in the accompanying illustration, the nameplate indicates whether the transformer is wound for one or three phases, the intended power source frequency, the type of material used in the windings (CU stands for copper), the enclosure type, any listings that apply, such as UL or CSA, and a variety of other information essential to the proper installation and operation of the transformer.

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Apparent Power Rating

The actual power used by a transformer load is called true power and is measured in watts. However, transformers are rated for the amount of apparent power they can provide, rather than the amount of power used by any given load.

For a single-phase transformer, the apparent power rating is calculated by multiplying secondary voltage by the maximum load current. For a three-phase transformer, this value must be multiplied by the square root of 3, which is approximately 1.73.

The unit for apparent power is the volt-ampere, also called the volt-amp or abbreviated VA. However, because values of apparent power are often large, a transformer rating is often given in kVA (kilovolt-amperes). The kVA rating determines the current and voltage a transformer can deliver to its load under rated conditions without overheating.

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Percentage Impedance (% IMP)

The percentage impedance, % IMP, is used to determine the available fault current at the secondary terminals of the transformer. It is a ratio, not an impedance, that is determined during testing of the transformer. Because measuring the actual available secondary fault current would stress (and possibly damage) the transformer, the voltage on the primary is slowly increased from zero with the secondary shorted until the rated secondary current is reached. The percentage of the rated primary voltage that results in the rated secondary current flowing is the % IMP.

We can use the % IMP to determine the fault current that would flow if the full primary voltage were applied. For example, consider the transformer nameplate on the left. This 45 kVA, 480:240V, three phase transformer has a rated secondary current of 45,000 VA/(240*1.732) or approx. 108 A. When tested, the secondary terminals were shorted and the primary voltage was increased until 108 A flowed in the secondary. The primary voltage used to produce this current was 15.84 V, or 3.3% of the rated primary voltage. Because of the transformer winding ratio, if we applied 480 V to the primary, an available fault current of 108 A/0.033, or 3,272 A, would flow in the secondary. Page 2-5


Insulation Temperature Classes

As the accompanying illustration shows, there are four classes of insulation commonly used in low voltage distribution transformers as specified by ANSI and NEMA. Each class is designated by a temperature rating that is determined by adding an ambient temperature of 40°C, the allowed temperature rise, and the allowed winding hot spot value. An allowed hot spot is included because the interior of the winding is hotter than its exterior.

The transformer’s insulation class rating identifies the temperature that the insulation can withstand without damaging the transformer or shortening its service life.

Keep in mind that the 40°C ambient temperature shown in the chart is the maximum ambient temperature. The actual ambient temperature should not exceed an average of 30°C over a 24-hour period. In addition, the altitude should not exceed 3300 feet above sea level.

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Temperature Rise

Temperature rise is the average number of degrees Celsius (C) that a transformer’s aluminum or copper windings increase over the ambient temperature when the transformer is loaded to its nameplate rating.

Many Siemens low voltage distribution transformers are designed for a 150°C temperature rise. Siemens dry type transformers rated 15 kVA and above with insulation rated for 220°C can be designed for a lower temperature rise of 80 degrees or 115°C, as shown in the accompanying illustration.

Transformers with a lower temperature rise are more expensive to manufacture, so they cost more initially. However, they generate less heat, operate more efficiently, and last longer than transformers with a higher temperature rise rating. This means that lower temperature rated transformers typically have a lower total cost over their service life.

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Transformer Efficiency

The efficiency of a transformer is the percentage of the applied energy that is transferred to the load. All transformers have core and conductor losses that cause some of the applied energy to be dissipated in heat.

Although any distribution transformer transfers most of its applied energy to its load, because distribution transformers are often in constant operation, most is not good enough. As shown in the accompanying table, the U.S. Department of Energy (DOE) 2016 efficiency standard (DOE 10 CFR PART 431:2016) now requires efficiencies that exceed those in the NEMA TP1 standard mandated prior to 2016.

The DOE 2016 standard applies to distribution transformers up to 2,500 kVA manufactured after January 1, 2016; however, this does not include a number of transformer types. For example, autotransformers, drive isolation transformers, non-ventilated transformers, and several other types are excluded.

.

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Terminations and Taps

Both high and low voltage windings are terminated in the transformer wiring compartment. The high voltage terminations are identified in accordance with NEMA standards as H1, H2, and H3. The low voltage leads are identified as X1, X2, and X3. The neutral lead is designated as X0. The connection diagram on the transformer nameplate shows the proper connection points for series and multiple connections and tap settings.

Taps are frequently provided on the primary winding to change the turns ratio when it is necessary to compensate for high or low line voltage. The number of taps and their placement depends on the specific ratings for the transformer. Larger transformers typically have more taps. The taps available for a transformer are shown on the transformer’s nameplate.

The accompanying illustration shows two examples of tap arrangements for Siemens dry type transformers. The term FCAN (Full Capacity Above Nominal) indicates that the associated taps are for use when the supply voltage is above the nominal voltage (480 VAC in this case) to achieve the desired voltages on the low voltage leads. Likewise the term FCBN (Full Capacity Below Nominal) indicates that the associated taps are for use when the supply voltage is below the nominal voltage. Page 2-9


Sound Levels

All transformers produce an audible hum when energized. The hum is produced by vibrations in the core laminations and other components as the magnetic fields vary with the alternating current.

The NEMA ST20 average sound levels for self-cooled, ventilated distribution transformers (K Factor 1, 4, or 9) are shown in the accompanying chart. The decibel (dB) scale is non-linear, but, as a frame of reference, the sound level of a typical conversation at three to five feet is 60 dB and the sound level from typical vacuum cleaner is about 70 dB.

As this chart indicates, the higher the power rating for the transformer, the greater the average noise level. Transformers can be custom designed to operate at lower sound levels if required. However, the transformers construction is not the only factor that affects noise. The following items should be considered when planning a transformer installation.

• Locate the transformer away from areas where noise will be a problem.

• Locate the transformer where the sound is not significantly increased by sound reflection.

• Install the transformer so that vibrations are not transferred to the structural parts of the building or through openings.

• Isolate the transformer by using flexible couplings and conductors.

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Non-Linear Loads and Harmonics

A linear load is a load that does not distort the applied signal when operated within specifications. Linear loads include induction motors, resistive heating elements, and other circuits with passive components.

Non-linear loads such as computers, variable speed drives, solid-state motor starters, solid-state lighting ballasts, and many other circuits have active components that distort the applied sine wave.

Whenever a sine wave is distorted, harmonics are produced. A harmonic is a signal which is a multiple of the fundamental frequency. Therefore, the second harmonic of a 60 Hz signal is a 120 Hz signal, the third harmonic is a 180 Hz signal, etc.

The specific harmonic frequencies produced and the amplitude of each signal varies with the circuit, and not all harmonics affect electrical distribution systems the same. However, in general, harmonics shorten the service life of a transformer by causing additional heat in transformer windings. In addition, selected harmonics cause additional heat in the neutral conductor.

Because of these factors, many transformers need to be de-rated in accordance with ANSI/IEEE procedures when used with non-linear loads. An alternative approach is to use transformers with a K-Factor rating appropriate for the loads employed. Page 2-11


K-Factor Transformers

K-Factor rated transformers are transformers designed to operate with specific levels of non-linear loading without de-rating.

These transformers do not reduce the harmonics, but they are designed with windings and oversized neutrals that can handle the harmonic currents and have better ventilation to more effectively dissipate the heat. In addition, K-Factor transformers also have an electrostatic shield to attenuate transient noise.

As shown in the accompanying chart, a transformer’s K-Factor is a measure of its ability to operate with non-linear loads without de-rating. Therefore, the K-Factor needed for a specific application depends on the extent to which non-linear loads are employed. Because the cost of manufacturing a transformer increases with the K-Factor, transformers with different K-Factors are available. The most common ratings for K-Factor transformers are K-4, K-13, K-20, and K-30.

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Selection Factors

Several factors must be considered when selecting a transformer for a specific application. The most basic factors are power frequency, supply voltage, and load requirements.

For example, select a transformer to match the power frequency, (60 Hz in the U.S. and some other countries, 50 Hz elsewhere) .

Select a transformer to match the supply voltage and the number of power phases.

Select a transformer to match the load requirements for voltage and current. This data may be available from equipment documents or nameplates. Using load voltage and maximum current values you can then determine the correct transformer power rating. If the requirements are not known, the formulas shown can be used to determine the required transformer kVA rating.

The potential for future increases in load should be taken into consideration when selecting a transformer. A good rule of thumb is that if the calculated kVA is 90 percent or more of the transformer rating, choose the next larger size.

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Distribution Transformer Options

While it is not in the scope of this course to cover all the possible options and their advantages and disadvantages, the accompanying chart provides examples of options for consideration.

In addition to the items shown in this chart, if the transformer will be operated with ambient temperatures above 40°C or at altitudes above 3,300 feet, a standard transformer must be de-rated or a special transformer design must be used.

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Chapter 3 – Siemens Transformers


• Transformer Types

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Dry Type Distribution Transformers 600 Volt Class

Siemens dry type distribution transformers 600 volt class are rated from 0.25 to 167 kVA for single-phase transformers and 3 to 1000 kVA for three-phase transformers. A variety of primary and secondary voltage ratings are available. Transformers are designed, manufactured, and tested in accordance with ANSI, NEMA and IEEE Standards and are UL Listed. All units are fungus resistant.

Encapsulated• The self-cooled kVA rating is suitable for 30°C average, 40°C maximum

ambient temperature.• Single-phase transformer ratings from 0.25 kVA to 25 kVA and three-phase

transformer ratings from 3 kVA to 15 kVA are available.• Transformers feature indoor/outdoor enclosures with integral wall mounting

brackets and either a 135°C rise, 180°C insulation system or a 95°C rise, 130°C insulation system.

Ventilated• Single-phase transformer ratings from 15 kVA to 167 kVA and three-phase

transformer ratings from 15 kVA to 1000 kVA are available.• Indoor NEMA 1/3R enclosures with 150°C rise and 220°C insulation

systems are standard.• Most three-phase designs (15 kVA through 75 kVA) and single-phase

designs (15 kVA through 50kVA) include primary and secondary terminal lugs

• Single-phase transformers up to 167 kVA and three-phase transformers up to 750 kVA are Seismic certified for floor mounting. Page 3-2


Low Voltage Distribution Transformer Types

Siemens products include the following low voltage distribution transformer types with a variety of options for each type.

• Single-phase Transformers• Three-phase Transformers• Motor Drive Isolation Transformers• Sentron Power Centers• Harmonic Mitigating Transformers• Buck-Boost Transformers

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Single-Phase and Three-Phase Transformers Features

Encapsulated Transformers

• UL-listed designs (UL 506)• Totally enclosed, non-ventilated, heavy gauge steel

enclosure• Core and coil completely embedded within a resin

compound for quiet, low temperature operation• Encapsulation seals out moisture and air• UL-listed indoor/outdoor enclosure features integral wall

mounting brackets• Rugged design resists weather, dust, and corrosion• Efficient, compact, lightweight, easy to install• Flexible wiring leads that terminate within the bottom

wiring compartment• Large wiring compartment on the bottom with convenient

knockouts• High quality non-aging electrical grade core steel• Precision wound coils

Ventilated Transformers

• UL-listed designs (UL 1561)• Designed for indoor NEMA 2 installations.• NEMA 3R enclosures suitable for outdoor locations

available as an option• Core and coils are designed with UL-listed high-

temperature materials rated for 220°C; standard units feature 150°C winding temperature rise

• Optional low temperature rise of 115°C or 80°C winding temperature rise for increased efficiency and additional overload capability

• Rugged sheet steel enclosure per UL1561, UL506 standards with removable panels for access to the internal wiring area

• Neoprene noise dampening pads isolate the core and coil from the enclosure

• Optional drip shield/weather shield and wall brackets available

• High quality grain-oriented, non-aging silicon steel core for three-phase units

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Transformers Ampere Ratings

Page 3-5


Motor Drive Isolation Transformers

Drive isolation transformers are engineered for both AC variable frequency drives and DC motor drives. The motor drive isolation transformer isolates the motor from the line and handles the added loads of the drive-created harmonics.

These transformers are designed to accommodate the electrical and mechanical stresses, regenerative current reversals and frequent short circuits, inherent in severe drive duty cycles. The cores are designed to meet the inrush characteristics of drive applications. Windings are braced to withstand the mechanical stress and overload capacity needed. The separate primary and secondary windings provide electrical isolation between the incoming line and the load which minimizes line disturbances, feedback, and transients.

Common optional modifiers include low temperature rise, electrostatic shields, copper windings, thermal switches, wall mounting brackets and drip shields.

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Sentron Power Centers

A Siemens Sentron Power Center is a pre-wired combination of a primary breaker disconnect, dry type shielded transformer, secondary breaker disconnect, and secondary power panel all in one convenient package.

Using a Sentron Power Center save time, space, and money by eliminating the need to individually assemble, mount, and wire these components. Simply add the branch breakers and you’re ready to go. Both plug-on and bolt-on breaker panels are available. All Sentron Power Centers are rated for indoor and outdoor use.

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Harmonic Mitigating Transformers

Siemens Sentron harmonic mitigating transformers (HMTs) are designed to meet the needs of modern powerdistribution systems that contain a large percentage of non-linear equipment that produces harmonics.

Sentron HMTs are specially designed to operate under high non-linear load conditions and have the additional benefit ofimproving the overall power system reliability.

Sentron HMTs are only available in three-phase with either one or two secondaries.

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Buck-Boost Transformers

A Siemens buck-boost transformer has four separate windings; two primary windings and two secondary windings . It can be used an autotransformer or with isolated primary and secondary windings.

As an autotransformer, the unit can be set up to buck (decrease) or boost (increase) a supply voltage. Because autotransformers transmit line disturbances directly, they are prohibited in some areas by local building codes.

When used with isolated primary and secondary windings, these transformers can accommodate a high voltage of 120, 240, or 480 volts. For units with two 12 volt secondaries, two 16 volt secondaries, or two 24 volt secondaries, the output can be wired for either secondary voltage or as a three-wire secondary.

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Siemens Low Voltage Distribution TransformerCatalog Numbers

Siemens low voltage distribution transformer catalog numbers have up to 28 positions. The first 5 positions are for required basic ratings. The remaining positions identify options.

The accompanying diagram shows the positions for each of the possible values.

For information about each of these values, refer to the Siemens SPEEDFAX catalog which is available on the Siemens Industry, Inc. web site.

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Course Completion

This course covered the following topics:Chapter 1 - Introduction

• Overview• Transformer Basics

Chapter 2 – Transformer Information• Specifications and Ratings

Chapter 3 – Siemens Transformers• Transformer Types

This course has covered the topics shown on the left. Thank you for your efforts. You can complete this course by taking the final exam and scoring at least 70%.

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Basics of Low Voltage Distribution Transformers-Chapter 1 · Transformers come in a variety of...

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Transcript of Basics of Low Voltage Distribution Transformers-Chapter 1 · Transformers come in a variety of...