10+ Shree NM Electricals Interview Questions and Answers

The capacity of the transformer in our plant is 500 kVA.

• Our plant's transformer has a capacity of 500 kVA.

• This allows us to efficiently power our equipment and machinery.

• We regularly maintain and monitor the transformer to ensure optimal performance.

The electrical equipment in our plant includes generators, transformers, switchgear, motors, control panels, and lighting fixtures.

• Generators: Used to produce electrical power.

• Transformers: Used to step up or step down voltage levels.

• Switchgear: Used for controlling, protecting, and isolating electrical equipment.

• Motors: Used to convert electrical energy into mechanical energy.

• Control panels: Used for monitoring and controlling various electrical systems.

• Lighting fixtures: Us...read more

We use Allen Bradley PowerFlex VFD drivers in our plant.

• Our plant uses VFD drivers for controlling the speed of AC motors.

• Allen Bradley PowerFlex VFD drivers are known for their reliability and performance.

• These drivers offer a wide range of features such as overload protection, fault diagnostics, and energy savings.

• We have installed these drivers in various applications such as pumps, fans, and conveyors.

• Our maintenance team is trained to troubleshoot and repair these driver...read more

Buchholz relay is used in transformer near conservator tank.

• Buchholz relay is a type of oil and gas actuated protection relay used in oil-immersed transformers.

• It is installed between the transformer tank and the conservator tank.

• It provides protection against internal faults such as insulation breakdown or arcing within the transformer.

• The relay operates based on the detection of gas or oil flow within the transformer.

• It triggers an alarm or initiates a trip signal to discon...read more

PLC and HMI can communicate through various protocols such as Ethernet/IP, Modbus, Profibus, etc.

• PLC and HMI can be connected through a physical cable or wireless connection

• PLC sends data to HMI through the chosen protocol

• HMI displays the data received from PLC and sends commands back to PLC

• Programming software is used to configure the communication settings

• Examples of protocols used for communication are Ethernet/IP, Modbus, Profibus, etc.

DOL starter is a direct online starter used to start and stop motors. VFD is a variable frequency drive used to control motor speed.

• DOL starter is a simple and cost-effective method of starting motors

• It provides full voltage to the motor during starting

• VFD is used to control the speed of the motor by varying the frequency of the power supplied to the motor

• It is more efficient than other methods of speed control

• VFDs are commonly used in HVAC systems, pumps, and conveyor belts

Output VFD drops due to various factors such as overloading, voltage fluctuations, and motor issues.

• Overloading of the motor can cause the VFD output to drop.

• Voltage fluctuations can also cause the VFD output to drop.

• Issues with the motor, such as a faulty winding, can cause the VFD output to drop.

• Inadequate cooling or ventilation can cause the VFD output to drop.

• Incorrect programming or settings can cause the VFD output to drop.

VFD output formula calculates the output voltage and frequency of a variable frequency drive.

• The formula is Vout = Vin x (2/√3) x (Fout/Fin)

• Vout is the output voltage, Vin is the input voltage, Fout is the output frequency, and Fin is the input frequency

• The formula assumes a three-phase system

• The output frequency can be adjusted to control the speed of the motor

• Example: If Vin is 480V, Fin is 60Hz, and Fout is 30Hz, then Vout would be 240V

Types of motors include AC, DC, stepper, servo, and induction. Motor protection includes overload, overvoltage, and overtemperature.

• AC motors are commonly used in household appliances and industrial machinery

• DC motors are used in electric vehicles and robotics

• Stepper motors are used in printers and CNC machines

• Servo motors are used in robotics and automation

• Induction motors are used in pumps and fans

• Overload protection prevents damage from excessive current

• Overvoltage protect...read more

Transformers are of two types - step-up and step-down. Protection methods include overcurrent, overvoltage, and differential protection.

• Step-up transformers increase voltage while step-down transformers decrease voltage

• Overcurrent protection is achieved through fuses or circuit breakers

• Overvoltage protection is achieved through surge arresters or lightning arresters

• Differential protection is used to detect internal faults in transformers

• Examples of transformers include power ...read more

Encoders are devices that convert motion into an electrical signal.

• Encoders can be rotary or linear

• They work by detecting changes in position or motion

• They can be absolute or incremental

• Examples include optical encoders and magnetic encoders