Electrical & Electronics

Question 1

What is SCCR?

Answer 1

The value of lowest FLC (fault Current) in an electrical box is the SCCR of that box

Question 2

FLC

Answer 2

fault current is any abnormal electric current. For example, a short circuit is a fault in which a live wire touches a neutral or ground wire.

Question 3

4 steps in determining SCCR

Answer 3

Step 1 – Determine the short circuit current rating (SCCR) of each component or combination in the power circuit. (SB4.2)
Step 2 – Determine whether feeder circuit components limit fault current (SB4.3) circuit-protective devices, like the fuse or circuit breaker.
Step 3 – Determine overall short circuit current rating for industrial control panel (SB4.4.).
Step 4 – List the SCCR marking on the control panel nameplate (SB5.1).

Question 4

some sections of UL standard

Answer 4

• UL 891 – Deadfront Switchboards
• UL 1058 – Drawout ACBs
• UL 67 – Panelboards
• UL 98 – Disconnect Switches
• UL 489 – Molded Case Circuit Breakers
• UL 508A – Industrial Control Panels
• UL 508E – Self Protecting MMPs
• UL 508F – Combination Motor Controllers (CMCs)

Question 5

z Panels for Industrial Machinery are rated:
1- 600V or less
2- 40°C
z UL 508A Industrial Rating does not include panels for Hazardous Locations “NRBX” which is covered under UL698A

Question 6

Branch Circuit vs. Feeder Circuit

Answer 6

Branch circuit: it is the utility circuit; it is the part of the circuit that starts from the load (e.g. motor) and ends at the first short circuit protection (Branch Circuit Protection Device or BCPD). Feeder circuit: indicates the supply circuit, i.e. all the elements upstream of the BCPD.

Question 7

Control Circuit vs Power Circuit

Answer 7

Protection: Power circuits are equipped with protective devices like circuit breakers, fuses, and contactors to ensure safety and control overloads and short circuits. Control Circuit: Function: Control circuits are responsible for managing the operation and coordination of industrial equipment

Question 8

Components not to be considered in Short Circuit Current
Ratings

Answer 8

Transformers, reactors, dry-type capacitors, resistors, varistors,
and voltmeters

Question 9

SB.4.3 Feeder Components that limit Short Circuit

Answer 9

1- Power Transformers
2- Current Limiting Circuit Breakers
3- Fuses

Question 10

CPD and top 5 CPDs

Answer 10

Circuit Protective Device
1- DC CONTROL CIRCUIT PROTECTION
2- MOLDED CASE CIRCUIT BREAKERS
3- MINIATURE CIRCUIT BREAKERS
4- MOTOR CIRCUIT PROTECTORS
5- MOTOR PROTECTION CIRCUIT BREAKERS

Question 11

Arc Flash Study

Answer 11

An arc flash study is an engineered incident energy analysis defined to establish safety protocol for qualified electrical personnel required to work on electrical equipment and circuit parts that cannot be placed in an electrically safe work condition