Protective Device
This occurs when too much current flows in a circuit due to faulty equipment or too many appliances connected.
What is an overload?
This switch has one pole and one throw and is used to control one circuit from one position.
What is an SPST switch?
What is the unit for Reactive Power?
VAR
What is the meaning of NC and NO in a direct on line starter and give an example of each?
Normally closed - e.g STOP SWITCH
Normally open- e.g START SWITCH
What is a Transformer?
A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnet induction
This type of fault happens when the live and neutral wires touch directly, causing a very large current flow.
What is a short circuit?
This switch can control two separate circuits at the same time using one action.
What is a DPST switch?
What is the function of the auxiliary contact in the control circuit?
To maintain a DOL circuit after the START button is released
State the formula for calculating the transformer ratio?
Np/Ns = Vp/Vs
Name one protective device that melts and breaks the circuit when excessive current flows.
What is a fuse?
Name the switch that can change connections between two outputs or paths.
What is a DPDT switch?
State two losses in a Transformer
A 5 A fuse is connected in a circuit carrying 10 A. What will most likely happen?
The fuse will melt or blow and disconnect the circuit.
This control device uses an electromagnet to open or close contacts automatically.
What is a relay?
Explain the difference between overload current and short circuit current
Overload current is a small excess current over time caused by too many loads, while short circuit current is a very large sudden current caused by direct contact between conductors.
State one advantage of a reed relay.
It operates quickly / uses low power / has sealed contacts.