Circuits, Beakers, and Fuses

Question 1

What type of fuse is class K-5?

What type of fuse is class RK-5?

What type of fuse is class RK-1?

Answer 1

• K-5 is one time fuse
• RK-5 is Time delay fuse
• RK-1 is current limiting fuse

Question 1

Explain the following fuse ratings

Current?

Voltage?

Interrupting rating?

Answer 1

• Current - the amount of current that should cause the fuse to blow
• Voltage - the maximum amount at which the fuse can safelty interrupt current flow
• Interrupting rating - higest current the fuse can safely interrupt at rated voltage (must be higer than short circuit current of the curcuit it is used with.

Question 2

What is this? Explain what is does

Answer 2

Fusible disconnect switch

Provides overcurrent protection

Allows a circuit to be isolated

Allows a circuit to be locked out to be worked on safely

Question 3

What are these symbols?

Answer 3

A. Single fuse element

B) Three-pole disconnect Switch, ganged with Handle

C) Three-Pole fused switch with ganged handle

D) One Pole, Termal magnetic Ciruit Breaker

E) Three Pole circuit interupter, Ganged with handle

F) Three Pole, Termal magnetic circuit breaker, ganged with handle.

Question 4

what type of fuse is this?

Answer 4

Cartridge Fuse

Question 4

What is this circuit depickting ?

Answer 4

It is showing how a UPS operates

Question 5

Desribe some overcurrent conditions

Answer 5

• Short ciruit - term used to describe the condition that exists when current takes a low resistance / impedance “shortcut” and doesn’t pass through the intended load
• Overload- term used to describe a condition in which the amount of current is higher than normal for that circuit

Question 6

What should be consitered when installing control systems?

Answer 6

• All conductors should be terminated in a central location, such as a control panel.
• All conductors should terminate on a numbered terminal block,
• Iniitial expense higher, but the payback is shorter downtime to troubleshoot

Question 7

What are some methods to protecting a circuit?

Answer 7

• Circuits are protected from overcurrent conditions by fuses and circuit breakers
• Fuses have a calibreated conductor that melts (is destroyed) by overcurrent
• Circuit breakers have mechanical contacts that open when an overcurrent is sensed

Question 8

What is this

Answer 8

Molded case breaker

Question 10

What are some things you should consiter when selecting cables?

Answer 10

• Cable and wire numbering
• Spare conductors in cables
• Cable segregation by voltage level
• Protection from induced “noise”
• Fire protection
• Bottom entry whenever possible
• Water in conduits

Question 11

What is an UPS

Answer 11

A uniteruppted Power supply

It is a backup power supply used to protect against power failures

Question 12

What is this ?

Answer 12

Control Transformer

Question 13

What are cartridge fuses made of?

Answer 13

calibrated element, filler materical and contacts

Question 14

Explain some aspects of circuit breakers

Answer 14

• Have mechanical contacts which open to interrupt a circuit when an overcurrent condition is detected
• contacts can be reclosed - usually manually
• Same ratings as fuses: current ,voltage, interrupting capacity
• some have undervoltage release coil which trip the breaker when coil voltage drops

Question 16

What are the four steps to remember with Control Circuit Development?

Answer 16

1. Know what the circuit is supposed to do.
2. Know the conditions required to start, control & stop the process(circuit logic).
3. Select, divide and isolate rungs by function.
4. Inputs on the left rungs, outputs on the right.

Question 17

Draw this image and tell me what it is.

Answer 17

It is a control transformer schematic

Question 18

Name some circuit breaker types

Answer 18

Circuit Interrupter- manually operated

Thermal - detects slight overcurrents over extended time

Magnetic - rapid response to instantaneous overcurrent

Thermal magnetic - Combines quailitys of both types