Posts Tagged ‘transfer switch’

How to select a sectionalizer

February 12th, 2016 | 1 Comment | Posted in Electrical Safety
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Last day, A.N. one of our contributors told us how to select an Automatic Transfer Switch (ATS). Now, here he’s back to give us some knowledge about selecting a selectionizer.

If one of you want to share knowledge with the community to keep it alive, just send us a mail!


Sectionizers are protective devices that are used in medium voltage distribution systems to automatically isolate faulted sections once an upstream recloser or breaker has interrupted the fault current. The self contained protective devices are usually installed downstream of a recloser in the distribution circuit.

The Sectionizers do not have the capacity to break the fault current and are usually used in conjunction with other backup devices such as reclosers and circuit breakers that have the ability of breaking the fault current. When in operation, the sectionalizer counts the number of interruptions occurring on the circuit. It does this by monitoring the number of times the recloser opens.

Figure 1 : Typical sectionalizer connection

Figure 1 : Typical sectionalizer connection


How to Select an Automatic Transfer Switch (ATS)

January 5th, 2016 | 5 Comments | Posted in Panel Building
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megaphone1To begin year 2016, we’re glad to publish this article by a new member from Kenya, specialized in electrical installations, maintenance and repairs.

He told us about his experience (20 years!) and he kindly sent us this article about automatic transfer switches. We tought it was interesting and decided to post it on the blog.

Remember you too can send us material and be published in the Electical Engineering Community blog! Just send us a mail.

For now, let’s enjoy this article…

The automatic transfer switches are used to automatically transfer the load from the utility power to a secondary or backup power source whenever power goes out, or as required.

A careful selection of the switch ensures adequate capability, safety, and maximum reliability under both normal and emergency conditions. As such, one must consider technical factors such as the size, type of load, continuous current rating, voltage rating and style. In addition, the price, compatibility and reliability must be considered.

Soft Loading Transfer Switch

October 10th, 2013 | Make a comment | Posted in Panel Building
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Here’s 7th part of Nasir’s tutorial which chose to go deep into the sea of these transfer switches and study each and every type in detail, in the easiest possible way.

Don’t forget, you can also send us your works, studies, tutorial, debates or even an article about your work experience

A Soft Load Power Transfer switch is a type of closed transition power transfer switch in which the switch synchronizes the two power sources and then makes connects them in parallel so that an uninterrupted supply of power can be generated for the sensitive loads.

Working of a Soft Loading power Transfer Switch

The functioning of the switch is such that it can connect both the power sources in parallel mode, as well as when a short time period has passed (almost somewhere near 100 milliseconds), it becomes able to switch to one contact only.

For e.g. if the soft loading power transfer switch has to change its contact from the primary power source to the backup set of generators, then it will synchronize the set of two power supplies and momentarily connect them in parallel, like a closed transition transfer switch momentarily closes its contact with both the power sources at such times.

Afterwards, the soft loading power transfer switch will open its contact from the primary power supply and maintain the contact with the backup generator set, after inculcating a preset load value in the generator.

So if any power supply fails in any condition, the load will automatically set to the available power, from either of the two sources, in which ever is it available.

Soft loading power transfer switch inculcated in a home unit with all the accessories is shown below:

Soft Loading Transfer Switch 1


Closed Transition Transfer Switch

October 4th, 2013 | 1 Comment | Posted in Panel Building
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Last time, Nasir taught us about the working and advantages of an Open Transition Transfer switch, now it’s all about the working and advantages of a Closed Transition Transfer Switch.

A Closed Transition transfer switch also operates on the same principle as that of an open transition switch, except the fact that the delay which is incorporated in the open transition switch has been eliminated and hence the contacts occur without any delay in the time.

Working of a Closed Transition Transfer Switch

The process occurs such that if the power is being supplied from the primary power source, and it’s time for the contact to break due to a break in the power, then first the contact will be made with the backup power supply.

i.e. the alternate source from which the load has to be transferred is closed and the afterwards the contact will open from the main power source.

In this way there is a brief moment in which both the contacts are closed, so that there is no such time in which the power supply is interrupted.

This process can be shown as follows:

Closed Transition Transfer Switch 1


Open Transition Transfer Switch

October 1st, 2013 | 1 Comment | Posted in Panel Building
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Today, in the 5th part of his tutorial, Nasir studies the working and advantages of an Open Transition Transfer switch. Let’s check what he has to teach!


Open transition transfer switches are designed to switch between the normally present power supply; which is being supplied to our homes by the power stations, and the backup arrangement in the form of some generator or anything.

They operate between these two supplies depending upon the conditions, if the primary power supply is available or not.

They have a switch which monitors the power sources and keeps a check so that whenever the primary source fails to deliver the power, it immediately switches to the backup set of generators.

But the major difference that it has from the closed transition transfer switch is that, this switching is not performed immediately, instead there is a short break between the opening of one contact and the closing of the other.


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