ILT166 test 1

a transformer has a primary voltage of 7200 v and a secondary voltage of 360v. what is the turns ratio?

20:1

a wye- connected secondary has a phase voltage of 277.14. what is the line voltage?

480v

a simplified schematic diagram of three phase transformer connections is called a ___ diagram

one line

a wye-delta transformer has a secondary phase voltage of 480v. a delta connected resistive load has a resistance of 12 ohms in each leg, what is the current in each load leg?

40 a

a transformer has a 2:1 turns ratio. 240 V is applied to the primary. what is the secondary voltage?

120V

if a single three phase transformer of the proper ratings is not available, three single phase transformers can be connected to do the job, when this is done, the connection is called

three phase bank

a transformer tape wound core is also called a ___ core

toroid

The magnetically operated device that can change values of voltage, current, and impedance without changing frequency is the _____.

transformer

T/F In an isolation transformer, all windings will have the same number of volts per turn

true

a transformer has a 240V primary and a 60V secondary. with a 5 ohm load connected, what is the primary current?

3A

dielectric oil performs what functions

acts as an insulator, prevents moisture formation, provides cooling

a transformer that does not isolate the out from the input is called a ____ transformer

auto

the industrial use transformer that normally has 240 v or 480 v primary and a 120v secondary is called a ___ transformer

control

the transformer that converts a high (7200V) voltage from the power company down to 120/240V for the homes and business is called a ___ transformer

distribution

in a transformer, even when there is no load connected, there will be some small current required to magnetize the core. this current is called ____ current

excitation

T/F When single-phase loads are tied to a three-phase transformer, the phase currents of the transformer will be automatically balanced

false

in three phase transformer connections, the high voltage leads are labeled with the letter __ and the lower voltage leads are labeled with the letter ___

h,x

when using an open delta with a center tapped transformer, one wire is the high leg. the high leg is the one that

has the highest voltage measured to ground

the amount of current that flows into a transformer primary when voltage is first applied is called ____ current

inrush

A transformer in which the primary and secondary are physically separated and not connected by a conductor is called a(n) _____ transformer.

isolation

most transformer cores are not made from a solid piece of metal. instead, they are assembled from many thin sheets of metal. this type of construction is called

laminated

a transformer supplying a house with 120/240 V has a secondary which is center tapped. the conductor connected to the center is called the ___ conductor

neutral

for installations that will have both three phase and single phase loads on a three phase transformer, the utility company often provides a ___ three phase transformer

open delta with one transformer center tapped

The transformer winding, which is the power input winding, is called the _____ winding.

primary

a delta-wye transformer has its ___ connected as a delta and its ___ connected as a wye

primary, secondary

a wye-delta transformer has its ____ connected as a wye and its ___ connected as a delta

primary, secondary

the transformer winding which is the output winding is called the

secondary

a transformer in which the secondary voltage is less than the primary voltage is called a ____ transformer

step down

a transformer in which the secondary voltage is more than the primary voltage is called a ____ transformer

step up

In a transformer, the turns of primary wire compared to the turns of secondary wire is called the _____ ratio.

turns

an open delta connection is made using ___ single phase transformers

two

In an open delta with single-phase loads, the high leg must be identified by _____.

using orange wire OR tagging

a transformer metal toroid is assembled by

winding a long continuous tape of metal into a spiral

a transformer tape wound core is assembled by

winding a long continuous tape of metal into a spiral

when connecting three transformers for three phase use with a delta secondary, a voltage test should be done before closing the secondary. the correct voltage reading is

zero volts