STE 15096 - Demountable Transformer

INTRODUCTION

The STE 15096 Experiment Pack enables fundamental behaviour and relationships governing transformers to be investigated.

The notes provided fully explain four experiments covering the relationships between the relative number of coils of primary and secondary circuits and the currents and voltages in these coils, the direction of primary and secondary currents, and induction heating.

CONTENTS

QTY            Description                                               

1              Tripod base                                       

1              Wax candle                                       

1              Coil 400 turns                    

1              Coil 1600 turns                          

1              “U” core                                    

1              Yoke for transformer                           

1              Connecting rod for transformer             

1              Coil 25 turns                                      

1              Ring, test - wax holder with handle               

1              Ring, aluminium                         

1              Ring, split, aluminium                 

EXAMPLE EXPERIMENTS

(all worksheets have necessary diagrams)

PRINCIPLES OF OPERATION

The Transformer is a four pole electrical device which uses as its basis of operation the fundamental phenomena of electromagnetic induction.

The transformer is highly important in very many applications, of which the most significant is the transport of electrical energy over large distances.

Ignoring ohmic resistive losses and parasitic currents in the transformer core the performance of the transformer is governed by the following relationships:

 Eqn 1:    V₁ : V₂ = N₁ : N₂                           Eqn 2:     I₁ : I₂ = N₂ : N₁

where N₁ and N₂  are respectively the number of coils in the primary and secondary coils , while V1, V₂  and I₁, I₂  are the voltage and current in the primary and secondary circuits.

Experiment 1

Relationship between voltage and number of turns (Eqn 1).

To verify equation 1) set up the equipment as illustrated in Fig 1.

Insert the 1600 turn coil into the first side of the U core, to form the primary, and into the second side insert the 400 turn coil as the secondary.

For this experiment, as for the following, an alternating voltage of 24V is to be applied to the primary 1600 turn coil.

Connect a voltmeter to the secondary coil so as to measure the secondary voltage, which, within the limits of error, should be one quarter of the voltage applied to the primary.

Reversing the two circuits, making the 400 turn coil the primary, the secondary voltage should now be 4 times that of the primary.

Experiment 2

Relationship between currents and number of turns (eqn 2))

To verify equation 2, the configuration shown in Fig 1 must be altered as follows:

Insert an ammeter in series into the primary circuit, using the 400 turn coil as primary, so that with 24V AC applied the current in the primary can be measured.

Insert another ammeter into the secondary circuit, using the 25 turn coil as the secondary, and include a series resistance of between 2 and 10 ohm into the secondary circuit.

It is recommended to use two universal multimeters, which will enable both currents and voltages to be measured, including both AC and DC measurements.

The experiment can be repeated, taking measurements of both current and voltage in both primary and secondary circuits.