How to properly size a motor circuit breaker? This article will tackle about the sizing of Inverse Time Circuit Breaker with regards to National Electrical Code (NEC). I have learned this not just in school, but also in review center for our national board exam. It's one of the essential topics you should know for future use especially in the design field. What is Circuit Breaker? Circuit Breaker is an over current protective device that can manually switch on/off and automatically trip when a short circuit fault occurs. Why do we need to size a circuit breaker? Circuit Breaker rating is sized according to its load/s. Thus, undersized circuit can always give false alarm to operation. While oversized can lead to equipment breakdown or
VFD vs Softstarter – An Interview Question
What are the differences between VFD and Softstarter? If you're planning to join a company with equipments or products like those mentioned above. You should study the differences between the them in different aspects. It would be probably asked during the interview stage. This is one of the questions that I encountered during job interview for a sales and distribution company. Aside from how to install and program it, to study the working principle is a must for an easy explanation. For the main difference, a Softstarter is commonly used in applications where there is a large inrush of current that could damage a motor while VFD controls and can vary the speed of a motor. This article will discuss more of their differences in terms of
Define RCCB – An interview question
What is RCCB and how does it work? This is one of the questions I have encountered during my job interview for a sales distribution company. Honestly, I had a hard time answering the question and just relied on the words itself. There is a specific purpose and explanation why they call it RCCB and its working principle. That actually made a way for me to study it and make an article for it. As the improvement of modern industry, I observed that the electricity is becoming more useful, but it also becoming more hazardous too! Do you know that it takes only few milliseconds for a strong electric current flowing through your heart to harm you? Think about this, if you’re using an
Overload Relay Sizing – part of RME review
In this article, I will explain to you how motor overload relay is sized according to National Electrical Code (NEC). I will be sharing with you what I have learned from college and review center when I took registered master electrician. What is an Overload Relay? Overload Relay is normally used for motor control as a protective device against overloading. It can be an electronic type or the conventional type that uses a bimetallic strip that will react to the amount of line current passing. It's wired in series with the power circuit for current sensing and has usually two contacts for signalling and command. Why do we need to properly size an Overload Relay? Overload relay must be properly sized
Ground, Earth vs Neutral
These three mentioned have essential use in the field of electricity. This article will identify the difference between them by knowing their specific purposes. For easy identification, normally ground wires are in green/yellow color while neutral wire in blue/white color. It may vary based on the country or standard you're working with and you should be aware of. Neatral and Ground Busbars Ground and Earth Ground and Earth are the same in puprose, it's just happened that the term Ground has been used by US while Earth by UK. Going back to its purpose, ground or earth is part of the Electrical Protection System where anything bonded to it is safe to touch as long as it's sized, installed and
How I conduct Motor Maintenance
This post will cover the standard procedure of motor maintenance, clearance from production and thereafter isolate the power supply and lock-out tag-out the equipment that I have experienced working different plants. To carry out the Preventive Maintenance activity as per given procedure and standard Preventive Maintenance sheet. I can say that companies have their own standard procedure based on their best practice and company they are working with. Even the some condition must be considered too when motor is in running condition and cannot be stopped, or should be swapped to other just for PM. But keep in mind that our goal for Preventive Maintenance is to test the motor for trending, to prolong it's lifespan by preventing fault to happen
ACB and VCB PM experience
This article will also discuss the differences between ACB and VCB. I'm going to share with you what I have experienced and learned about Air Circuit Breakers and Vacuum Circuit Breakers. Photos in this post were captured during maintenance activities for ACB and VCB in our low and medium voltage Switchgear. I'm grateful to experience and dismantle some parts to see what's more inside and how the parts are working to make it function. Photo showing the housing and internal parts of vacuum circuit breaker When you work in a substation and electrical rooms, switchgear is one of the common panel enclosure you could see. One of the main equipments in switchgear is circuit breaker either Air Circuit Breaker or Vacuum Circuit