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20 terms

Stephen Smith AC concepts review 3

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Step up transformers
increase the voltage in the secondary winding, when compared to the primary winding
Step down transformers
Decrease the voltage in the secondary winding, compared to the primary winding
The transformer ratio of a transformer with primary voltage of 240v and a secondary voltage of 40 v is
6 to 1
The transformer ratio of a transformer with primary turns of 500 and secondary turns of 1250
1 to 2.5
The secondary current will
be increased by four times
A danger tag placed on an electrical isolation device, may only be removed by
The person who placed it
The steps to isolate an electrical circuit are
Inform the customer, Identify the isolation device, Isolate the circuit, discharge stored energy, verify isolation, bond load side conductors to earth
The checks to be made before reconnecting supply to a circuit are
Check circuit continuity, check conductor terminal location, check terminal condition, check conductor condition, check circuit insulation resistance, check earth loop impedance.
The limited electrical licence of a refrigeration tradesperson allows him/her to complete the following work.
service and maintenance procedures on electrical circuits directly connected to refrigeration and air conditioning equipment, only.
Calculate the secondary current of a transformer with a ratio of 12 to 1 and a primary current of 10 amps.
120 amps
Determine the secondary power consumed by a transformer that consumes 800 watts in the primary coil.
800 watts
The secondary voltage being 20v.
120 amps
Secondary power 480 watts.
4 amps
Three types of circuit diagram are
schematic, wiring, block
Two sections of an electric circuit are
Control and power circuits
Two methods of connecting circuit components are
Series and parallel
Circuit loads are usually connected in parallel to ensure that
All loads are connected to full supply voltage
Switches in control circuits are commonly connected in series to ensure that
when any switch becomes open circuit, supply to the circuit load is disconnected.
Circuit loads are not connected in series because
Voltage drops across each circuit load in series, preventing loads from being connected to full supply voltage.
In a parallel circuit having 2 branches, load number 2 has a volt drop of 238 volts. Determine the supply voltage?
238 volts