Offline UPS Systems
The “Uninterruptable Power Supply” is also called as Standby Power Supply, since they stand by whilst the main power supply is working. These power supplies usually consists of inverters operating from DC storage source (like battery). In many applications like major computer installations, process control in chemical plants, hospital intensive care units continuous power supply is highly essential. In these applications, temporary power failure can cause a great inconvenience and economic losses. The UPS plays an important role in these situations.
There are various types of Uninterruptible Power Supplies available. Click here to know more about the Basics and Various types of UPS system. This post will explain about the Offline UPS system only.
The following figure shows the configuration of an offline UPS system. It is also known as Line-Preferred UPS or Passive Standby. The Offline UPS System is the simplest form of back up power systems.
Comparison of Inverters: VSI vs CSI
This post will discuss about the difference between Voltage Source Inverter and Current Source Inverter. Before proceeding further we will get the introduction about them.
What is meant by Inverter?
The inverter is the power electronic circuit, which converts the DC voltage into AC voltage. Inverters can be broadly classified into two types. They are
Voltage Source Inverter (VSI)
Current Source Inverter (CSI)
Power Electronics Basic Interview Questions with Answers:
In this post we are going to discuss about various Power Electronics Basic Interview Questions with brief answers…In this set, we will focus on Electrical Drives related questions…Before proceeding further we will give few tips to you…
 You may be visit here to prepare for the interview, for a company who involves industrial automation, motor control etc…
 What do you think, that the interviewer will expect from you?
He needs a candidate who has a basic knowledge of various DC and AC motors and understanding the operation of various special motors…
We had given various drives related interview questions here…
[Q] What is meant by Electrical Drives?
Answer: Systems employed for motion control are called as “Drives” and many employ any of the prime movers such as, diesel or petrol engines, gas or steam turbines, hydraulic motors and electric motors for supplying mechanical energy for motion control. Drives employing electric motors are known as ” electric drives”.
Here, We had given only the definition of electrical drive. But if you face this question in the face to face interview try to explain in detail. Draw the Block diagram of the electrical drive first. During the time, you recall about the basics and every part of the electrical drive system and explain as detail as possible. Click here to know about Electrical Drives basics and types
[Q] What are the different factors for the selection of electrical drives?
Steady state operation requirements
Transient operation requirements
Requirements related to the source
Capital and running cost, maintenance needs, life
Space and weight restrictions
Environment and location
Line Interactive UPS Systems
UPS – An Introduction:
A UPS is a device that maintains a continuous electric power supply to the connected equipment(load) by supplying power from a separate source when the main power supply is not available.
Click here to know more about basics and classification of UPS
Static UPS systems can be classified into three main categories:
 Online UPS system
 Offline UPS system
 Line Interactive UPS system
This post will discuss about the Line Interactive Uninterruptible Power Supply (UPS) only.
The Online UPS is explained in separate post. Click here to know more about the Online UPS.
The following figure illustrates the Line Interactive UPS configuration.
Online UPS Systems
This post will explain about the Online UPS systems. The Uninterruptible Power Supply Systems are generally classified as
- Static UPS systems
- Rotary (or dynamic) UPS systems
- Hybrid UPS systems
The Static UPS systems can be classified into three main categories:
[i] Online UPS
[ii] Offline UPS
[iii] Line Interactive UPS
This post will discuss about the Online Uninterruptible Power Supply (UPS) only.
The Line Interactive UPS is explained in separate post. Click here to know more about the Line Interactive UPS.
The following figure depicts the configuration of an online UPS system. It is also known as “double conversion UPS system”.
Silicon Controlled Switch (SCS): Basics, Operation, Application
This post will explain about one of the newly developed Power Semiconductor Device known as Silicon Controlled Switch [SCS]. It acts as a switch in the power electronic circuits and its switching operation (both turn on and turn off) can be controllable. That is the reason this device is called as Silicon Controlled Switch.
- The Silicon Controlled Switch (SCS) is a power semiconductor device similar to an SCR, but it is designed to turn off when a positive voltage/input current pulse is applied to an additional “Anode gate” terminal.
- The SCS can also be triggered into conduction mode by applying a negative voltage/output current pulse to the same lead.
- In addition to this, the Silicon Controlled Switch behaves just like an SCR ( ie, by applying positive voltage to the “gate” terminal we can turn on the device).