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Types of Transfer Switches

Madhavi Ghare Sep 26, 2018
A transfer switch switches the power supply form the main source to the secondary source during a power outage. These switches are of two basic types - manual and automatic. Here, we provide information about these two types and how they help in the transfer of the electrical power.
Electrical transfer switches are those switches which cause an electric system to switch from one power source to another. This is especially useful when the main power source gets disconnected due to any reason and you have a back-up or a stand-by power source.
The most common example is when the electric supply of a home or office switches from the regular supply of electricity, to generator power back-up in the case of a power outage. These are, therefore, also known as 'generator transfer switches'.
These switches are also useful at times when voltage changes are observed in the power supply. These voltage changes may cause a lot of damage to the internal circuits of any appliance.
In such conditions, the transfer switch transfers the power to a generator or a back-up power source, till the voltage has stabilized. These benefits have made them extremely popular among domestic and industrial users.

Types of Transfer Switches


These are generally toggle switches, which need to be manually switched on so that the power source gets transferred from one source to the other.
They can be used in places where power outage happens quite rarely, and loss of power does not cause any damage to the appliances or systems used.


These switches automatically transfer the power source from one to the another, when the primary source is disrupted or fluctuations are observed.
Thus, these are more convenient to use, as one does not have to manually toggle a switch or turn a knob to switch the power source. Automatic transfer switches are useful where even a small loss of power can cause a lot of damage in the system which his being powered by the electricity supply.
Automatic transfer switches have therefore found their popularity and usefulness in several industrial and commercial applications, where a constant source of power is necessary in the process.
Most of the electrical transfer switches in use are either manual or automatic or even a combination of the two. Nowadays, however, most people prefer the automatic transfer switches as it saves a lot of time and effort.

Methods of Electrical Transfer

Break Before Make

In this method, the transfer switch will break the contact from one power source before switching to the other power source. This break can be for a small or large amount of time, depending on the configuration of switch used. The advantage of this method is that it prevents backfeeding from the emergency generator into the electric power supply line.

Closed Transition

In this method, the transfer switch ensures that there is not much time gap in the power supply to the system, while it transfers from one power source to another. This is used in industrial and commercial applications, where even a small fluctuation in power can cause damage to the product or the system used with the electric power supply.
In this system, the generator runs parallel with the electrical power supply for a certain period of time. This enables the generator to take up the load while the power supply remains uninterrupted.

Soft Loading

In this method, a closed transition transfer switch method is used. However, the only difference is that the amount of load accepted by the generator is actively changed with this switching method. This is a more dynamic version of the closed transfer switch method of transfer of electrical power source.
Thus, it can be summarized form the aforementioned data that electrical transfer switches make life easier for common people, along with industrial and commercial organizations. They help to keep the supply of electric power smooth and in a continuous.