Cochin Kagaz Interview Questions and Answers

A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction.

• Transformers work on the principle of electromagnetic induction.

• They consist of two or more coils of wire, known as windings, which are wound around a core made of magnetic material.

• When an alternating current (AC) flows through the primary winding, it creates a changing magnetic field in the core.

• This changing magnetic field induces a voltage ...read more

There are mainly two types of motors used in elevators: AC and DC motors.

• AC motors are commonly used in high-rise buildings and have a longer lifespan.

• DC motors are used in low-rise buildings and are more energy-efficient.

• AC motors are more expensive than DC motors.

• AC motors have a higher starting torque than DC motors.

• Examples of AC motors used in elevators include induction motors and synchronous motors.

• Examples of DC motors used in elevators include shunt-wound motors and ...read more

Elevator is a vertical transportation device that moves people or goods between floors of a building.

• Elevators are powered by electric motors that drive traction cables or hydraulic pistons.

• They have safety features such as emergency brakes, overspeed governors, and door interlocks.

• Elevators can be controlled by various systems such as relay logic, microprocessors, or destination dispatch.

• Modern elevators also have features such as touchscreens, voice announcements, and desti...read more

AC drives control the speed of AC motors by varying the frequency of the electrical supply.

• AC drives use power electronics to convert AC power to DC power and then back to AC power at the desired frequency.

• Different types of starters include direct-on-line (DOL), star-delta, soft starters, and variable frequency drives (VFDs).

• DOL starters provide full voltage to the motor, while star-delta starters reduce the voltage during starting to reduce current and torque.

• Soft starters ...read more

Oil lubricant is used in elevators to reduce friction and wear on moving parts.

• Oil lubricant reduces friction between moving parts in elevators.

• It helps to prevent wear and tear on elevator components.

• Oil lubricant also helps to dissipate heat generated by friction.

• Different types of oil lubricants are used depending on the elevator's design and usage.

• Regular maintenance and oil changes are necessary to ensure proper elevator function.

A battery converts chemical energy into electrical energy. For example, a lead-acid battery used in cars.

• Batteries work by converting chemical energy into electrical energy

• Common types of batteries include lead-acid, alkaline, lithium-ion, and nickel-cadmium

• Lead-acid batteries are commonly used in cars and work by converting lead and lead oxide into lead sulfate

• Alkaline batteries use zinc and manganese dioxide to create a chemical reaction

• Lithium-ion batteries are commonly us...read more

The latest motor used in elevators is the permanent magnet synchronous motor (PMSM).

• PMSM is more energy-efficient and has a higher power density than traditional motors.

• It uses rare-earth magnets to create a magnetic field that rotates the motor shaft.

• PMSM is also quieter and requires less maintenance than other motors.

• Examples of elevators that use PMSM include Otis Gen2 and KONE MonoSpace 500.

Synchronous motors are used to maintain constant speed and power supply in industrial applications.

• Synchronous motors have a rotor with permanent magnets that rotate at the same speed as the stator's magnetic field.

• They are used in applications where constant speed is required, such as in electric power generation, industrial machinery, and robotics.

• Synchronous motors are also used in applications where precise control of speed and torque is necessary, such as in electric veh...read more