Mott Interview PRep Flashcards
What is Ohms Law?
Current and voltage are directly proportional (linear graph) -> resistance is constant i.e resistor. An example of a non-ohmic component is a filament lamp evident from the I-V graph
What is sustainable energy and some examples?
Energy derived from sources that meet contemporary needs without jeopardising energy access for future generations i.e solar, wind, hydro, geothermal. Finite energy sources/non-renewable energy sources include fossil fuels and nuclear.
Factors to consider when sizing LV cables
Be able to withstand a short circuit:
Depends on fault current amount, insulation of the cable, the time duration of the fault
Current carrying capacity:
Must be able to deliver the expected load current
Voltage drop across cable:
Cable has some resistances and reactances causing a voltage drop, should remain within an acceptable limit to ensure connected equipment function properly (i.e motor)
Insulation material:
Air cables require UV and mechanical protection, also protection against heat and moisture
Describe what three-phase is
The three phases are offset by 120 degrees so when the net signal is averaged out it is more constant/linear compared to a single sine wave.
Three phase power and resistance triangles (real, imaginary, complex)
P=(root3)IVcos(theta)
cos(theta)=power factors
theta=angle between voltage and current
More power for the same amount of wire
Constant torque
Difference between AC and DC transmission
DC:
-No need to frequency match when transmitting power between systems (no Hz in DC)
-Requires more infrastructure as power is generated and received in AC (DC converters required at both ends)
-Smaller cables required in DC as AC has skin effect (actual current only travels in a small ‘skin’ portion of the cable)
-No reactive power in DC so less losses
What is resilience in power systems?
Property of a system which enables the synchronous machines to respond to a disturbance from normal operating conditions and return back to normal condition.
Describe factors to consider in substation design
Circuit breakers: to isolate parts of a system for diagnostics or testing
Grounding components for protection against lightning or electrical surges
Busbar design: current carrying capabilities of the busbar, be able to withstand short circuit stresses (amount of short circuit current, time duration)
Transformer parameters: how high you want to step up the voltage (higher for longer distances)
Transmission line design: (extra infrastructure for DC as converters are required, DC doesn’t require frequency matching, less losses across a DC line because no reactance’s)
What kind of activities you expect to do on a daily basis while working at Mott MacDonald
Provide the clients of the company with technical support through each phase of development from design to construction to operation. I also expect to liaise with stakeholders such as investors and contractors. Design electrical systems used in rail projects such as alarms, implementing sensors across the rail network for remote access such as proximity sensors (ultrasonic), vision sensors like LIDAR, pressure gauges.
What are the biggest threats to the company? Who are our competitors?
I would say a lack or apprehension to innovate and incorporate new technologies into future projects is a threat as the companies that do take that risk could pull ahead in project quality/efficiency. Other consulting firms are competitors to Mott Macdonald such as Arup and Jacobs.
What are some considerations in railway infrastructure
location: does it impact local natural environments negatively such as negatively impacting ecosystems
demand: is there a demand for faster public travel in this area where it’s presence will generate a return
size: if there is a demand how large is it? how big is the local population?
Why do you want to work for us? What do you know about the job?
Company values such as sustainability and health and safety (not only physical but mentally with your mental wellbeing champions)
High profile projects such as the new Elizabeth line, helping build clean energy infrastructure in Somalia and Japan
My skillset and knowledge from not only my electrical engineering degree but also my key interest in sustainability (solar simulation projects). Also my experience working and leading in a team environment can prove useful.
Describe the skills you learnt in your plumbing work experience
Learnt how waste management systems are designed in residential buildings and their requirements (p-traps)
Learnt how to solder copper piping to repair leaks (abrasive to sand down the connection, apply flux, heat the pipe, apply the solder around)
Location of stop valves
Different materials used in waste systems such as ABS and PVC and how to properly prime PVC to ensure the glue properly adheres.
Liaised with clients to make sure they understood the scope of the project (how long it would take)
Where do you see yourself in 5 years?
I see myself progressing within the company to more managerial/senior roles where I will have more responsibility on projects and imparting my knowledge and expertise to train fresh engineers working at the company.
Gaining chartership and maybe pursuing my Masters degree alongside my standard work duties.
how to make buildings sustainable?
solar panels on buildings
renewable energy sources to power the buildings
harvesting rainwater for surrounding gardens
using sustainable materials (recycles or renewable)
healthy indoor environments with natural lighting and ventilation (non toxic materials)
