Fundamentals of Electromagnetic Relays

In electromagnetic relays, driving torque is created based on ____________and restraining torque is generally provided with the help of ___________.

• Electrical principle, springs

• Voltage, current

• Current, spring

• Voltage, spring

The minimum currents at which the relay armature is attracted to close the trip circuit is called ______.

• Set Current

• Rated current

• Pickup current

• All the above

In induction type relays, the net force applied to the disc increases with increase in __________.

• Supply voltage  

• Phase angle between fluxes

• Size of copper band

• Excitation current

The main function of the fuse is to

• Protect the line

• Open the circuit

• Prevent excess current

• Either (a) or (b)

Which is not considered as overload relay?

• Directional relay

• Thermal relay

• Soli state relay

• Magnetic relay

Torque produced in shaded pole structure induction type erlay is

• Proportional to square of the current

• Inversely proportional to the square the current

• Proportional to current

• Inversely proportional to the current

Which of the following relay is called as angle impedance relay?

• Time distance impedance relay

• Definite distance type impedance relay

• Reactance relay

• Admittance relay

An impedance relay is a  

• Directional restrained over current relay

• Voltage restrained over current relay

• Directional restrained over voltage relay

• Voltage restrained directional relay

Mho relay is

• Current restrained current relay

• Current restrained directional relay

• Voltage restrained directional relay

• Voltage restrained current relay

Differential relays are used to protect the equipment from

• Over current

• Over voltage

• Reverse current

• Internal faults