For various commercial installations, transformers are installed in order to either step up or step down the voltage levels that may be needed for the building.
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Following types of transformers generally are used in various commercial installations.
Usually, for single phase transformers they are usually rated for 750 to 5000 KVA while for 3-phase transformer it is 705 to 25000 KVA.
Primary voltages can usually be 2400V and more while secondary voltage is 480 to 13,800 V. Primary sides are in delta connection while the secondary is star connected while the neutral point is grounded.
- Primary-unit substation
The secondary end of the transformer usually is connected to switch the gear system which are rated for 1000 to 10000KVA and usually are 3-phase units.
The primary voltages are in the range of 6900 to138000V and secondary voltages are in the range of 2400 to 34500 V.
Usually, tapings are manually changed but option for automatic load tapping can also be done.
- Secondary-unit substation
The secondary parts are connected switchgear and boards of lower voltage ratings which is in the range of 112.5 to 2500 KVA rating with 3-phase unit.
Primary voltage range is within 2400 to 34500 V and secondary is 120 to 480 V. taps are usually changed manually.
Primary connections are in delta and secondary in star connection.
These transformers used in the network are rated for 300 to 2500KVA. Its primary voltage range will be between 4160 to 34500 and secondary voltages are 208Y/120V and 480Y/277V.
Their taps are mostly manually operated. Here too primary side is delta connected while secondary side is star connected.
Normally, this transformer is used outside buildings where any conventional unit substations will not be the right choice. These are either single or 3 phase units.
Since they are made of highly tamper-resistant construction, they do not need any fencing.
- Indoor distribution
These transformers are always used with panel boards and also, they are separately mounted. Their ratings are 1 to 333 kVA which is for single-phase units. For 3-phase units it is 3 to500 kVA.
Here both primary as well as secondary voltages are 600 V and little below. One of the most common ratios usually is 480 to 208Y/120V.