Transformers Exam 1 Prep

What are the 3 factors in a Transformer

• Primary Side

• Secondary Side

• Turns Ratio

Faraday’s Law of Induction,

if the magnetic field is in motion relative to
the conductors, then a voltage will be
induced in the conductors.

What is the induced voltage between the Primary and Secondary side when voltage is applied to the the Primary side

Counter Electro-motive Force

What causes CEMF to increase in a Transformer?

More turns equal more CEMF

What effect does the CEMF have on the Primary Coil?

CEMF causes Current flow to be less on the Primary coil. This is caused by the opposing forces of the CEMF

Can CEMF happen on both coils?

Yes, but only when the secondary coil has a load on it

Is there a physical connection between the Primary and Secondary side of a Transformer?

No, there is no connection between the Primary and Secondary sides of a 

Are the volts per turn in the Primary side of a Transformer equal to the volts per turn on the Secondary side of a Transformer

Yes, the volts per turn on the Primary is equal to the volts per turn on the Secondary side

What is the definition of a Transformer

A static device used to transfer energy from
one alternating current circuit to another.

Does the Frequency change in a Transformer?

FREQUENCY WILL REMAIN THE SAME.

Fleming's right-hand rule

determines the direction of induced current in a conductor moving through a magnetic field

Flemmings right hand Grip Rule

• Thumb points to the North

• Fingers point in the direction of the current

What rule Indicates that the magnetic Polarity is Dependent on the direction of the Electron flow

• Flemmings right hand Grip Rule

Fewer turns on or smaller conductor means

Low Flux

What determines the amount of Flux generated in a Core?

• Size of Conductor

• Number of Turns

What law states states that the magnitude of the induced emf in a conductor is directly proportional to the rate of change of magnetic flux linkage

• Faraday's Law

How is 1 Volts Created

1 turn of wire must cut through one line of Flux

How many moving parts are there on a transformer?

None

What is Lens Law of Induction

An inducted Voltage opposes the motion that created it

What can effect the Flux

• The dimensions of the core

• Type of material the core is made of

What Type of losses can happen in a Transformer?

• Iron or Core Losses

• Copper or Ohmic Losses

• Stray Losses

• Dielectric Losses

What type of losses can happen with a Iron or Core

• Hysteresis

• Eddy Currents

What is Hysteresis

• Losses due to magnetization or Demagnetization of the Core

• Energy lost in each cycle as the magnetization is reverse

• Reduced by manufacturing using low reluctance Materials

What is Eddy Currents

• The magnetic flux influences not just the windings but also any other conductive material

• Transformer core

• Metal cabinet

• Eddy currents flow in a circular manner and provide no productive power

Methods for Reducing Eddy Current Losses

• Using a laminated core instead of

a solid core

• Laminations increase the

  resistance of the conductive

  metal reducing the amount of

  eddy current flowing+

• This reduces the amount of heat

  produced by the core

What are Copper Losses

• Transformer Copper Losses due to electrical

  resistance in the windings (primary and secondary)

Methods to Reduce Copper Losses

• The larger the conductor the lower

  the resistance

• better cooling reduces

  the I2R losses

What causes Stray Loss

• Stray losses are due to the leakage

  field in the transformer

What causes Dielectric Loss

Dielectric Loss occurs due to failing insulation

values of the transformer

What are Losses Due to Leakage Flux

• Flux that does not cross the

  conductor cannot induce

  voltage

• This leakage flux adds to the

  inefficiency

What can be done to Reduce Leakage Flux

Placing the primary and

secondary windings on the

same leg of the core maximizes

the amount of flux crossing the

windings

What information can be found on the Transformer Nameplate

• Volt-Ampere (VA) or kilovolt-amperes (kVA) rating

• The voltage rating of both the primary and secondary circuits

• The impedance rating of the transformer

• The required clearances for transformers with ventilated openings

• The amount and kind of insulating liquid where used

Who sets the Standards for the information a Transformer Nameplate

• American National Standards Institute (ANSI)

According to ANSI rules What are the H1-H2…Leads

• H1-H2,,, are the High Voltage leads

According to ANSI rules What are the X1-X2…Leads

• X1-X2,,, are the Low Voltage leads

What do these Dot mean

• they indicate the Polarity

• Additive pWindings

Subtractive Windings