Transformers 3:2
A ? system is a control system without a grounded secondary in the control transformer.
floating
A(n) ? is a circuit that has more than one point connected to earth ground, with a voltage potential difference between the two ground points.
ground loop
A ? system is a control system with a grounded secondary in the control transformer.
grounded
A ? transformer has separate primary and secondary windings wrapped around a laminated core.
wound current
Which of the following is a common function of potential transformers?
All of the above
The maximum current on the secondary of a current transformer is ? .
5 A
Which of the following is a common application for variable transformers?
All of the above
A control transformer should never be protected on both the primary and the secondary.
F
Potential transformers are usually fairly large.
F
Which of the following is not a common application for current transformers?
Light controls
A current transformer should always have its secondary shorted when not connected to an external load.
T
It can be difficult to determine when a transformer is undersized because most troubleshooting measurements are taken when all or almost all loads in a circuit are OFF.
T
Potential transformers can be made with almost any turns ratio so that the voltage can always be reduced to 120 volts.
T
Standard variable transformers can be ganged in series or in parallel.
T
The reduced voltage from a control transformer provides a much safer environment for technicians working with the equipment.
T
Variable transformers are usually wired as autotransformers.
T
Which of the following is a factor that must be considered when selecting a control transformer?
a., b., and c.
A ? transformer is used to supply low-voltage, low-power circuits, such as for doorbells, annunciators, and similar systems.
bell
The motor is not starting properly. The motor operates when the motor starter power contacts are manually closed at the motor starter. The motor does not operate when the start push button is pressed or when a fused jumper test wire is connected from points 1 to 3. A voltmeter connected at points X1 and X2 indicates proper voltage. A voltmeter connected at points 3 and X2 indicates no voltage at any time. The ? is the most likely cause of the malfunction.
control circuit fuse
A ? is a transformer used to step down line current to make it easier to measure.
current transformer
Current transformers usually have ? winding(s).
one
A ? transformer is a precision two-winding transformer used to step down high voltage to allow safe voltage measurement.
potential
The most common control transformers have ? .
two primary coils and one secondary coil
A ? transformer usually consists of a wiper or brush that can be rotated across the windings.
variable
A(n) ? transformer is used to make fine adjustments to the output voltage.
variable
A(n) ? transformer consists of a secondary winding wrapped around a core and a primary sent through the opening in the core.
window current
