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65 Cards in this Set
- Front
- Back
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What are the three basic types of Transformer Construction |
Core shell and H type |
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What has the most leakage of flex and the least |
The core type has the most leakage of flux H type has the minimum |
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What are the two main reasons that Transformers are used |
To isolate one circuit from another To change the voltage of the circuit |
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How do you identify high and low voltage terminals |
The letter x represents low the letter H represents High terminals |
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What does Lenz law state |
The polarity of an induced voltage in a circuit will always be opposite to the effect that caused it |
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How can you calculate the windings for the secondary voltage |
Voltage required ÷voltage per turn |
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The CEC limits Class 2 Transformers to a maximum output of |
100 VA |
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What is the more common use for the transformer in the gas trade |
To change the voltage of a circuit |
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What is the ratio of Ep to Es in a Transformer |
It is equal to the ratio of turns in the winding |
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Why is the iron core of a transformer laminated |
To reduce the eddy current |
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What does the VA rating of a transformer represent |
The full load output |
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Where would you expect to find a current limiting Transformer |
The power supply for the control system on a furnace |
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What is the difference in how an analog metre is used for an amperage reading when compared to the way it is used for voltage reading |
The amperage reading is taken in series with the circuit voltage parallel to the circuit |
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Why is it important to zero an analog metre each time you are going to make a resistance reading |
This procedure ensures the metre will be starting from the zero for each resistance scale |
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How can you avoid Parallax error when taking a reading from a analog multimeter scale |
Move your eye over the pointers so the reflected image and the pointer lineup and the reflection can no longer be seen |
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How do better analog metres help you avoid Parallax error when you are establishing a circuit value |
Include a reflective section in the metre face |
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What is a clip-on ammeter actually measuring when it is used for an amperage measurement |
The strength of a magnetic field |
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How will you know which scale of analog multimeter is the one you should be reading |
Compare the scale to the selector switch |
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How will you know what units are being measured with a digital metre |
The LCD readout includes the operation being performed and the range selected |
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What are two ways of Transformer Maybe short-circuited |
Overheating overloading |
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What do manufacturers recommend as maximum loading factors of the device that are connected to the secondary side of the dry Transformer used for controls |
80% |
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How are the Lamentations of a transformer core kept electrically separated from each other |
Varnishing each section or place paper between the layers and varnish the sections |
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What is the purpose of laminating the core of a dry Transformer |
It keeps Eddy loss to a minimum |
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Which of the following conditions is most likely to be the cause of primary windings opening in a Step Down Transformer |
High current flow in the secondary windings |
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What is reactive power in relation to the output of a transformer |
Power is used to create an electromagnetic field |
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What is Parallax error |
This is the variance when viewing an analog metre at an angle |
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What is the biggest cause of wire insulation breakdown in the coil of a transformer |
Too much heat generated in and around the Transformer |
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What do the classifications of a b f the temperature and H indicate on a Transformer |
The temperature rise rating of the Transformer |
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What is the recommended maximum amp draw of a Step Down Transformer |
80% of the VA rating |
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When a Step Down Transformer burns out from too much amp draw what has actually burned out |
The primary coil |
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If the amp draw of a transformer secondary coil were taken with a clamp-on amp metre and the reading was too low to register what would you do |
Use a ten wrap multiplier and don't forget to divide your answer by 10 |
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Transformers are under a thousand VA what are they rated in |
VA |
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Transformers that are over a thousand V A are rated in |
KVA |
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What problem would be created if there is a voltage unbalance |
It will ultimately shorten the motor life due to overheating |
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When tagging out a disconnect for an electrical motor or an appliance who should have keys for the lock you install |
You and you alone |
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What are the three basic components of the resistance start motor |
Frame the stator the rotor and the centrifugal switch |
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Which part of the motor is the stator |
This is where the run and axillary windings are located |
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What is the purpose of the centrifugal switch in the motor |
The shuts off the axillary winding when the motor has reached the proper speed |
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When does the centrifugal switch activate |
At about 75% of the rated speed of the motor |
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Spell real how would the run and start windings be connected to the power supply |
In parallel to each other |
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How would the centrifugal switch be connected to the start windings |
In series |
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How would the direction of rotation be reversed in a resistance split phase motor |
Interchange the Run winding or the start winding leads |
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What is the major difference between a capacitor start motor and a permanently split capacitor motor |
The capacitor is not switched out of the circuit in the permanently split capacitor motor |
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Where would you expect to find a shaded pole motor |
The induced draft fan in a furnace |
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Which direction will a shaded pole motor spin |
Toward the Shaded Pole |
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How can a shaded pole motor be reversed |
Disassemble the motor and turn the motor around |
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Which motor has the lowest starting torque |
A shaded pole motor |
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Shock that will create ventricular fibrillation of the heart |
100-200 Mv |
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When making repairs what is the first thing you should do |
Shut off the power when examining equipment were making repairs |
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What is service Factor |
The multiplier used to calculate how much over the nameplate rating the electric motor can be driven without overheating |
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Na |
Na |
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What creates the rotating magnetic field in a three phase motor |
Two magnetic fields produced by the start and run winding currents are out of phase with each other and build to a maximum value at different times |
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Formula for RPM |
(60 hertz) Frequency x voltage ÷number of poles |
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To Value capacitated motor may also be referred to as |
Capacitor start capacitor run motor or two capacitor motor |
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If H terminals are connected to the load the Transformer is being used as a |
Step up Transformer |
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Can Transformers operate using DC current |
No |
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What percentage are Transformers efficient |
95 - 98% |
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Name the five types of motors |
Single phase Motors, capacitor start induction run motor, permanent split capacitor, to Value capacitor motor, and shaded pole motor |
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What are the characteristics of a single phase motor |
High starting current Low starting torque Reversible Used with easy to start loads such as blower squirrel cages Don't have multi top speed regulation |
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What are the characteristics capacitor start induction run motor |
Low starting current High starting torque Reversible Use with hard to start loads such as air conditioners compressors Not to be used with speed control |
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Characteristics permanent split capacitor |
Has no centrifugal switch, the capacitor is in the circuit Low starting current, good power factor Low starting torque Reversible Used on blower squirrel cages Multi speed Taps over speed control Less maintenance as there are no centrifugal switch |
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Characteristics to - value capacitor motor |
Low starting current High starting torque, good power factor speed control not practical reversible used for high starting torque lodz like conditioning compressors we're High horsepower readings are required |
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Characteristics of shaded pole motor |
Speed control is obtained by varying the voltage low starting torque poor power factor efficiency is low 5% - 35% used for low horsepower venting fans cannot be reverse but reversible models are available |
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What are the three main parts of a single phase resistance split phase induction motor |
The stator, the frame, the rotor, and the centrifugal switch |
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Transformer transferring energy from one AC circuit to another at the same frequency (without moving Parts)in a action referred to as |
Mutual induction |
