Head Press Heating Tray Flashcards
What is a GG fuse
General purpose fuse
What does a GG fuse protector from?
Overload
Short circuit
What are gg fuses designed to protect?
Cables and equipment in both industrial and residential applications
How does a Gg fuse work in overload conditions?
If the current exceeds the fuses rated value for a prolonged period the fuses element heats ip and melts breaking the circuit
How does a Gg fuse protect from short circuits?
If a short circuit occurs, the fuses blows almost instantly preventing damage to cable and equipment
How does a Gg fuse protect from arcing?
Fuse is packed with quartz sand helping extinguish the arc
Why are Gg fuses used in the heating tray over Am fuses?
Am fuses are designed to deal with a high initial current inrush from motors. The heating tray is a resistive load so doesn’t have this large initial current inrush
Am fuses only protect against short circuits and require external overload protection
How does a contractor work? 3 steps
- Coil energisation
A magnetic field is created when the control voltage is applied to the coil. This field pulls in the contact towards the fixed contacts closing/completing the circuit
- Load activation
Once the contacts close current flows energising the connected load
- Coil deenergisatiob
When the control voltage is removed the magnetic field collapses and the contact returns to its intial position
Why are suppressors used in contractors?
Used to prevent a back EMF into the control circuit. This did generated when the feild on the contactor coil collapses causing an inductive kickback
Why are 2 contacts used on the head press heat tray?
Historical faults - single contact arced itself shut mean power was supplied constantly resulting in high temperatures as danfloss unit disconnected
Why do we torque things? Motors contacts ect
🔴 ensure good electrical contact reducing risk of loose connections that lead to arching voltage drops and overheating
🔴 loose connections increase resistance leading to inefficient power transfer and failures
🔴 increased resistance leads to excess heat and fires ect
🔴loose connections lead to vibration and cause further mechanical issues
🔴too high torque can strip threads and damage insulation
🔴 designed for specific torque ratings
What talk is required in the contactors?
Found on the faceplate of contact
What is a CT and what does it measure?
Current transformer
Electric current in power systems
How does the CT work?
The Ct has a secondary winding that mutually interacts with the cable. This induces a scaled down current proportional to the cable windings. The secondary current is then interpreted by the simocode
What is the power supply of the tray?
400v ac from buzz bars
What is the main function of circuit breakers?
To protect electrical circuits from damage
Circuit breakers serve various protection functions including overload, short circuit, ground fault, and arc fault protection.
What does overload protection do?
Trips when the current exceeds the safe limit
This prevents overheating of the electrical circuit.
What happens during short circuit protection?
Quickly shuts off power if a short circuit occurs
This action prevents damage to wiring and equipment.
What is ground fault protection?
Detects leakage currents and trips to prevent electric shock
This is crucial for personnel safety.
What does arc fault protection do?
Stops power if an electrical arc is detected
This reduces the risk of fire.
Name two types of protection that circuit breakers provide.
- Personnel Safety
- Equipment Protection
Circuit breakers help protect people from electric shocks and prevent damage to electrical equipment like motors and transformers.
What type of circuit breaker is mentioned?
MCB
MCB stands for Miniature Circuit Breaker.
List advantages of an MCB.
- Reliable Protection
- Automatic Reset
- Fast tripping time
These features make MCBs a preferred choice for protecting electrical circuits.
List disadvantages of an MCB.
- Limited to low current ratings
- Sensitive to overload
- No protection against ground faults
These limitations may require additional protective measures.
How does thermal protection in a circuit breaker work?
Uses a bimetallic strip that bends when heated
This bending eventually causes the contacts to open, interrupting current flow.
What triggers the magnetic protection in a circuit breaker?
Rapid increase in current due to a short circuit or surge
A magnetic coil generates a force that opens the breaker quickly.
What is a Solid state relay? (K11)
A solid state relay is an electronic switching device that performs the same function as electro mechanical relay but without moving parts use a semiconductor component such as transistors and Triax to switch electrical circuits on off
How does an SSR work in reference to the input output and isolation?
Input the SSR is activated by low-voltage signal apply to the input terminal
Isolation the LED light is received by photodiode or phototransistor inside the SSR. This creates an electrical isolation between the control circuit and load circuit preventing electrical noise of voltage bikes from damaging the control side.
For output the photo dial activates a fire Rister which switches the high power load circuit on off
What are the advantages of a SSR?
Not moving parts
Fast switching
Long lifespan
What are the disadvantages of a SSR?
generate heat
Limited voltage and current ratings
What does the K11 SSR monitor?
Temperature monitoring
What does the K12 SSR provide idication on?
MCC faults
What is a simocode?
Communication device that connects the mcc tray to the dcs system via profibus
How does the simocode communicate to THE DCS?
Communicates to the dcs via profibus! This rallies on cyclic and acyclic data exchange
In relation to the simocode what is cyclic data transfer?
Cyclic data exchange refers to real time data between simocode and DCs
Data typically exchanged under cyclic includes:
Motor status
Currrent, voltage power ect
Operating hours and load status
Train signals
