4th Stpe SSQ Flashcards
What is the equation for determining a transformers turn ratio?
Vp-Np
————
Vs- Ns
Primary voltage divided by secondary voltage.
Primary number of turns divided by secondary number of turns.
What is the purpose of a transformer tap changer?
To raise and lower secondary voltage by changing the turn ratio.
How is rotation check and determine?
At the customers panel from left to right at the customer panel
What is the maximum weight allowable for a closed-delta 300 KVA transformer bank on a 50- foot wood pole using a transformer mounting bracket? What is the minimum diameter pole for this application?
4200 lbs
11 inch minimum diameter
What is the maximum weight allowable for a 2-1 face transformer bank hung on a wood pole using a transformer bracket?
1600 lbs total weight limit.
Describe the AC electrical characteristics of impedance.
Impedance opposes the flow of electrical current in an AC circuit.
It is made up of two components: RESISTANCE & REACTANCE
Calculating Full Load Amps single phase and three face
KVA•1000 KVA•1000
———— —————
E s E s • 1.73
Calculating Fault Duty
Full Load Amps
————-———
Impedance
Calculating Turn Ration
V p
——
V s
What is a high leg? And how is it identified?
The night leg is the highest face to ground voltage. And is identified with orange tape at the cable or bus.
In a three-phase circuit, what is a grounded leg? Where is it located in the customers panel?
It’s a phase that has been grounded. And is located in the middle position at the customer panel.
When and why is rotation checked?
Rotation is checked before de- energizing to identify rotation of the three phase equipment, and after anergizing to double check rotation is the same as customers.
How is improper rotation corrected?
Swap any two phases with out disturbing the high leg.
What is the safe working load of a 1 1/8” 2 in one braid polyester core and cover winch line?
7000 lbs
What is the working load limit of a hand line sheave?
1000 lbs
