Basic Transformers

Some common sized for the primary lead wire are #6 or #4 copper and for the secondary lead wire is #4/0 insulated copper

Some common sized for the primary lead wire are #6 or #4 copper and for the secondary lead wire is #4/0 insulated copper (Copy)

Transformer Oil

Used for cooling and insulating the transformer's windings

Impedance

Voltage not billable to the customer

Polarity

an indication of direction of current flow from a terminal at any instant.

On a Transformer the units serial number stays with the core and not the tank if it is to be re-worked.

On a transformer the units serial number stays with the core and not the tank if it is to be re-worked. (Copy)

On an underground transformer nameplate, the primary coil voltage is printed in reverse order.

On an underground transformer nameplate, the primary coil voltage is printed in reverse order. (Copy)

There is a direct relationship between the number of turns in each winding and the amount of voltage changed from primary to secondary.

There is direct relationship between the number of turns in each winding and the amount of voltage changed from primary to secondary. (Copy)

To determine the size of the transformer you need , determine the following requirements for you transformer: 1.) Load Voltage - secondary voltage 2.) Load Current/Amps 3.) Type of load (single or three-phase) 4.) Line Voltage - primary voltage 5.) Voltage drop

To determine the size of the transformer you need , determine the following requirements for you transformer: 1.) Load Voltage - secondary voltage 2.) Load Current/Amps 3.) Type of load (single or three-phase) 4.) Line Voltage - primary voltage 5.) Voltage drop (Copy)

Two Primary types of Transformers

1.) Conventional Transformer 2.) CSP or Completely Self-Protected Transformer

Main Parts of the Transformer

1.) Core 2.) Winding 3.) Pressure Relief Valve 4.)Internal Fuse

1 Horsepower

746 watts

A transformer will not work on direct current (DC)

A transformer will not work on direct current (DC) (Copy)

Pressure Relief Valve

Allows the lineman to manually release pressure within the tank prior to opening the tank for inspections or pulling the bayonet fuses if equipped. It's main and most important purpose is to serve as a means for pressure to rapidly escape the tank in case of an internal fault.

Overhead transformers

Also known as pole mounted transformers, have points of terminations, called bushings, where the conductors are attached. The H1 and H2 high voltage bushings are located on the primary side and the x1,x2,x3 low voltage bushing are located on the secondary side, The x2 bushing by industry standard is the neutral bushing. The positions of the x2 and x3 bushing are determined by the polarity of the transformer

Transformer

An electrical device that changes one value of AC voltage into another value of AC voltage. In its simplest form it consists of three components: a primary winding, a secondary winding and a core.

Back-feed is the most important factor to consider when hanging and connecting or disconnecting and removing transformers. If a secondary bushing or riser is accidentally energized, the primary bushing is energized at primary voltage.

Back-feed is the most important factor to consider when hanging and connecting or disconnecting and removing transformers. If a secondary bushing or riser is accidentally energized, the primary bushing is energized at primary voltage. (Copy)

Four steps to paralleling: 1.) Ensure both transformers are fed off the same primary phase. 2.) Phase out the secondary cuts. 3.) Jumper the secondary cuts. 4.) Disconnect the transformer to be worked on.

Four steps to paralleling: 1.) Ensure both transformers are fed off the same primary phase. 2.) Phase out the secondary cuts. 3.) Jumper the secondary cuts. 4.) Disconnect the transformer to be worked on. (Copy)

Copper

Has the highest conductivity of the commercial metals

It is essential to always de-energize a transformer prior to performing maintenance or inspections.

It is essential to always de-energize a transformer prior to performing maintenance or inspections. (Copy)

KVA

Kilovolt ampere

Many older transformers contain chemicals knowns as PCBs which was used in the past to cool and insulate transformer windings until the United States stopped them from being produced due to evidence found that the chemical was a danger to the environment. You should always be aware of the type of insulating fluid in a transformer when working with older transformers.

Many older transformers contain chemicals known as PCBs which was used in the past to cool and insulate transformer windings until the United States stopped them from being produced due to evidence found that the chemical was a danger to the environment. You should always be aware of the type of insulating fluid in a transformer when working with older transformers. (Copy)

On single bushing pole mounted and single phase pad mounted transformers, the case ground is required for correct operation of the transformer by providing an adequate and complete path for electricity to flow through the primary winding. On two bushing pole mounted and three-phase pole mounted and pad mounted transformers, the case ground is required for safety of personnel, both linemen and the public. The ground connection should always be the FIRST connection made on any transformer.

On single bushing pole mounted and single phase pad mounted transformers, the case ground is required for correct operation of the transformer by providing an adequate and complete path for electricity to flow through the primary winding. On two bushing pole mounted and three-phase pole mounted and pad mounted transformers, the case ground is required for safety of personnel, both linemen and the public. The ground connection should always be the FIRST connection made on any transformer. (Copy)

Nameplate

One of the most important parts of a transformer. It has information a line worker must know to select, transport, hang and connect the transformer.

Polarity on a transformer refers to the direction of current flow through the 2 coils. It is set by the manufacturer and cannot be changed in the field.

Polarity on a transformer refers to the direction of current flow through the 2 coils. It is set by the manufacturer and cannot be changed in the field. (Copy)

Pressure Relief Valve is installed on transformers to relieve the internal pressure in the transformer before opening the Bay-O-Net fuse.

Pressure Relief Valve is installed on transformers to relieve the internal pressure in the transformer before opening the Bay-O-Net fuse. (Copy)

Prior to installing a transformer you should always do the following: 1.) Ensure the desired primary voltage is chosen 2.) Ensure the desired secondary voltage is chosen 3.) Ensure that the impedances are within 10% if banking or paralleling 4.) Determine the weight of the transformer for rigging purposes.

Prior to installing a transformer you should always do the following: 1.) Ensure the desired primary voltage is chosen 2.) Ensure the desired secondary voltage is chosen 3.) Ensure that the impedances are within 10% if banking or paralleling 4.) Determine the weight of the transformer for rigging purposes. (Copy)

Procedures for connecting and disconnecting transformers: 1.) Connect all ground and neutral connections first 2.) Ensure customer's load is disconnected; open service disconnect, remove meter, disconnect service leads, open man breaker if accessible, etc. 3.) Energize the primary side of the transformer; close the cutout, connect primary tap, etc. 4.) Using a voltmeter, check the secondary voltage between each phase and neutral/ground. It is critical to ensure proper voltage to the customer before connecting their load. 5.) Connect the customer's load; close service disconnect, install meter, close in breakers, connect service leads at transformer, etc.

Procedures for connecting and disconnecting transformers: 1.) Connect all ground and neutral connections first 2.) Ensure customer's load is disconnected; open service disconnect, remove meter, disconnect service leads, open man breaker if accessible, etc. 3.) Energize the primary side of the transformer; close the cutout, connect primary tap, etc. 4.) Using a voltmeter, check the secondary voltage between each phase and neutral/ground. It is critical to ensure proper voltage to the customer before connecting their load. 5.) Connect the customer's load; close service disconnect, install meter, close in breakers, connect service leads at transformer, etc. (Copy)

The KVA of the transformer should be equal to or greater than the KVA of the load to handle present requirements and to account for future expansion or future increase in load. However, care must be taken to ensure that the transformer is not too large because this will cause relatively excessive core losses in theorem of heat which wastes energy and can damage the transformer. Oversizing is not effective.

The KVA of the transformer should be equal to or greater than the KVA of the load to handle present requirements and to account for future expansion or future increase in load. However, care must be taken to ensure that the transformer is not too large because this will cause relatively excessive core losses in theorem of heat which wastes energy and can damage the transformer. Oversizing is not effective. (Copy)

The National Electric Safety Code requires that all systems less than 750 volts be grounded.

The National Electric Safety Code requires that all systems less than 750 volts be grounded. (Copy)

The National Electric Safety Code requires that the ground resistance shall not exceed 25 ohms. The national electric safety code also requires that a ground be no smaller than 5/8 inches in diameter and no less than 8 feet long.

The National Electric Safety Code requires that the ground resistance shall not exceed 25 ohms. The national electric safety code also requires that a ground be no smaller than 5/8 inches in diameter and no less than 8 feet long. (Copy)

The bushings on a transformer are connection points from the windings on the inside to the conductors on the outside

The bushings on a transformer are connection points from the winding son the inside to the conductors on the outside. (Copy)

The fused cutout is important because it: 1.) Protects the transformer agains heavy overload currents and short circuits. 2.) Clears a faulted transformer from the line allowing the line to remain energized 3.) Indicates where the problem is when troubleshooting

The fused cutout is important because it: 1.) Protects the transformer agains heavy overload currents and short circuits. 2.) Clears a faulted transformer from the line allowing the line to remain energized 3.) Indicates where the problem is when troubleshooting (Copy)

The magnitude of the voltage induced in a transformer secondary depends upon the turn's ration of the transformer. Turns ration is a comparison between the number of turns on the primary winding and the number of turns on the secondary winding.

The magnitude of the voltage induced in a transformer secondary depends up the turn's ratio of the transformer. Turns ratio is a comparison between the number of turns on the primary winding and the number of turns on the secondary winding. (Copy)

The nominal voltage should always be on the back of the transformer

The nominal voltage should always be on the back of the transformer (Copy)

The purpose of an arrester is to limit the surge voltages on equipment by diverting surge current and returning the device to its original status.

The purpose of an arrester is to limit the surge voltages on equipment by diverting surge current and returning the device to its original status. (Copy)

The tank of every transformer should be grounded to eliminate the possibility of obtaining induced voltage from it or being injured by accidental grounding of the winding to the tank. Grounding lugs are usually provided.

The tank of ever transformer should be grounded to eliminate the possibility of obtaining induced voltage from it or being injured by accidental grounding of the winding to the tank. Grounding lugs are usually provided. (Copy)

Diversity Factor

The transformer size and design must be selected and installed according to the maximum load of the consumer. When determining the size, you must account for the fact that the customer will not be operating at maximum load for long periods of time

The type of fuse link refers to the rate in which the fuse will melt under over-current conditions. (K = Quick) (T = Tardy)

The type of fuse link refers to the rate in which the fuse will melt under over-current conditions. (K = Quick) (T = Tardy) (Copy)

Secondary Winding

The winding that is connected to the load

Primary Winding

The winding that is connected to the source

There are six trees that should be used when checking the continuity of a transformer: 1.) H1 to H2 - Yes 2.) H2 to X1 - No 3.) H1 to Tank - No 4.) X1 to CG - No 5.) X2 to X1 - Yes 6.) X3 to X2 - Yes

There are six trees that should be used when checking the continuity of a transformer: 1.) H1 to H2 - Yes 2.) H2 to X1 - No 3.) H1 to Tank - No 4.) X1 to CG - No 5.) X2 to X1 - Yes 6.) X3 to X2 - Yes (Copy)

Three reasons you parallel two transformers: 1.) To provide capacity to serve the load when a larger transformer is not available. This is seldom used today but was once a very common practice. 2.) To provide continuous service while one transformer is being worked on. 3.) To temporarily restore service if a transformer goes defective, it may be necessary to tie two transformers together to pick up the load of the defective one.

Three reasons you parallel two transformers: 1.) To provide capacity to serve the load when a larger transformer is not available. This is seldom used today but was once a very common practice. 2.) To provide continuous service while one transformer is being worked on. 3.) To temporarily restore service if a transformer goes defective, it may be necessary to tie two transformers together to pick up the load of the defective one. (Copy)

Transformers have no moving parts. They transfer alternating current (AC) power from one winding to another by electromagnetic induction.

Transformers have no moving parts. They transfer alternating current (AC) power from one winding to another by electromagnetic induction. (Copy)

Transformers will handle overloads up to 200% of their rated KVA capacity for a short period of time under certain conditions.

Transformers will handle overloads up to 200% of their rated KVA capacity for a short period of time under certain conditions. (Copy)

When dealing with Underground transformers the primary bushings are H1A and H1B. The secondary bushings are x1, x2, x3. Primary side is always on the left.

When dealing with Underground transformers the primary bushings are H1A and H1B. The secondary bushings are x1, x2, x3. Primary side is always on the left. (Copy)

When grounding pad mounted transformers the ground bus conductor should be wire brushed before connecting to the tank lugs, ground rod connector, and neutral bushing connector.

When grounding pad mounted transformers the ground bus conductor should be wire brushed before connecting to the tank lugs, ground rod connector, and neutral bushing connector. (Copy)

When transporting a transformer to job location, always make sure that you read the nameplate for the weight before loading. When loading and unloading the transformer, check the weight of the transformer and use appropriate slings prior to lifting a transformer. Make sure that the transformer is placed on the truck in a secured location. Often times transformers are damaged by falling off of the back of trucks.

When transporting a transformer to job location, always make sure that you read the nameplate for the weight before loading. When loading and unloading the transformer, check the weight of the transformer and use appropriate slings prior to lifting a transformer. Make sure that the transformer is placed on the truck in a secured location. Often times transformers are damaged by falling off of the back of trucks. (Copy)

You should always buss a transformer on the ground before making the lift.

You should always buss a transformer on the ground before making the lift. (Copy)

Nylon Slings

are preferred for lifting transformers and should be lifted by the manufacturers lift points

Bay-O-Net fuse

designed to energize and de-energize the secondary coil or secondary side of the transformer. When the Bay-O-Net fuse is removed, the secondary side will be de-energized but the primary side will remain energized.

Fuse link

gives the fused cutout its ability to protect the transformer from over-current faults

CSP or Completely Self-Protected Transformer

has a built-in-low-voltage circuit breaker.

Additive Polarity

is standard for all single-phase distribution transformers 200 KVA and below having a primary voltage rating of 8660 volts and below.

Subtractive Polarity

is standard for all single-phase distribution transformers above 200 KVA regardless of the primary voltage rating.

Conventional Transformer

needs an external protective fused device or cut-out switch for protection from fault current

fused cutout

protects the transformer agains current overloads and show circuits. It is mounted on the primary line leading to the transformer

Lightning arrestors

these may be installed to protect the transformer from high voltage surges. This device creates a path to allow the surge to bypass and dissipated into the ground.