This article describes the all-round information about Pole Mounted Transformer, its working principle and other vital facts. Pole mounted transformers are distribution transformers mounted on an electric pole.
A distribution transformer alters high voltage coming from power stations to 220/120 V for use in distribution systems. One of its types is Pole Mounted Transformer. These are mounted on a power pole made of wood or concrete and at the same level with overhead cables. The range of these transformers can vary from 16 to 100 kVA.
What is pole mounted transformer?
Pole Mounted Transformers are a type of breadbox distribution transformers having mounted on an electric service pole of wood or concrete. They are held usually at the level of the upper wires.
Pole Mounted Transformers are rated anywhere between the range of 16 kVA to 100kVA. They can step 11,000 to 33,000 volts down to an apparently lower voltage of 400 volts. Generally home distribution systems, low volume commercial sites in rural areas utilize pole mounted transformers.
How does a pole mounted transformer work?
Pole Mounted Transformers are smaller in size. In PMTs, the power coming from the station gets connected to the insulator. After that, it gets attached to the GO ( gang operator) switch.
Some PMTs don’t have a go switch due to sparking issues. Then the line goes to drop-off fuse and next joins the primary winding of the transformer. Finally 240 V is received from the secondary side which gets connected to the MCCB and subsequently to the home distribution systems. MCCB protects the circuit from any hazards.
Pole Mounted Transformer- FAQs
How do powerline transformer work?
A transformer steps up or down the electrical energy flowing across a power grid. In the distribution system, it reduces the power supply through power lines to a level more apt for residential and commercial use.
In normal operation, electricity flows to the transformer on the side of the high voltage where it enters the inductor coil, usually tied near a metal. As electricity flows through this coil, it creates a varying magnetic field that attracts the electrical energy of the other coil.
How are pole transformers wired?
Pole Mounted Transformers have their wiring like any other distribution transformer. One end of the transformer is fixed with the source in the single phase connection and the other end is joined to the high voltage line.
Even some single phase PMTs are part of three phase systems. Three phase PMTs can have delta or wye wiring. They have return paths through a neutral wire joined to the source’s neutral point. The substation from which the power is coming, has wye connection with the secondary winding. Secondary is grounded as a safety measure.
What liquid is inside a transformer?
The liquid inside the transformer, often referred as transformer or insulator oil, is a substance of high insulating capability. It primarily insulates, works as a coolant and prevents corona discharge.
The main chemical used in traditional transformer oil is Polychlorinated Biphenyls or PCBs that is highly toxic. Currently most of the transformers use non-toxic mineral oils. These oils act as coolant for carrying heat from transformer windings to the case. Also, the oils are good insulators between the windings that reduce copper losses.
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Do transformers draw power when not in use?
The transformers are not in use means they are in no load state. They still draw some insignificant amount of power due to copper and iron losses. This is generally the reactive power measured in kVAR.
In a real transformer, when AC current flows, magnetic field is generated and some resistance is there. This is called impedance and factors like core material, air gap, number of turns etc. are responsible for it. Even in no load condition, magnetizing current causes very small I2R losses( eddy current loss and copper loss in winding).
Read more on…How Do Transformers Increase Voltage To Decrease Current: Exhaustive FAQs
How does a transformer operate?
Transformer is an electric device responsible for transforming voltage from one circuit to another keeping the power and frequency of the AC current intact. It utilizes the principle of mutual induction.
A transformer usually have two windings- a primary and a secondary. The AC current is passed through the primary, which creates magnetic field. The magnetic field, upon reaching the secondary coil due to mutual inductance, creates electromotive force. So we get a voltage either stepped up of stepped down at the secondary coil.
Read more on….Mutual Inductance Transformer : Mutual Inductance Equivalent Circuit and 10+ Critical FAQs
What is the role of transformers in the electric power grid?
An electrical power grid is a network connected by distribution and transmission lines that supplies electricity to the consumers. It has three main parts- electricity generation, its transmission and distribution.
A transformer converts the supplied input voltage to a higher or lower output voltage. It is a vital device in large power systems like power grids that provides electricity to people. Power generated at the substation should to be stepped up for long distance transmission and then stepped down in households. Transformers make these tasks possible.
How much copper is in a power line transformer?
The amount of copper in a power line transformer depends upon the rating of it i.e. its kVA, winding currents and voltages etc. Sometimes the material’s magnetic flux density is also taken into account.
Let us take an example of a transformer with 100 kVA rating and total weight 600 kg. For three phase transformers, the copper and the iron mass should be almost equal. So we can estimate that around 100 kg out of 600 kg will be taken for the hardware and insulating substances etc. So out of rest 500 kg, 250 kg copper can be there.
Can a transformer get power from the power source when it is at no load?
A transformer connected to a power supply but in no load condition will pull some current in the secondary coil, and have some losses. So there is a power loss in the transformer even in no load.
The main loss is due to the AC magnetic field set by the mains. There is a copper loss due to current in the primary and resistance to the primary. The unloaded primary of the transformer is usually flexible, but the current is flowing and there is a resistance component due to the limited conductivity.
Read more on….How Does A Transformer Work:Modularized Insights,Exhaustive FAQs
Does a transformer draw any current when nothing is connected to the secondary?
Even in no load condition, a small amount of current is drawn to the primary winding of the transformer, to generate the magnetic flux required for the magnetic field. This current is called as “no-load current”.
The No-load current is almost 3-5% of the total current load and it is responsible for the losses in the transformer. These non-load losses includes following losses:
- Core loss (iron/ fixed): It is the sum of eddy current loss and hysteresis loss
- Copper loss: It is the I2R loss caused by no load current
Pole Mounted Transformer specifications:
The distribution Pole Mounted Transformers are instated above the ground level on electric poles. Different providers have their own specifications for the transformer depending upon single phase or three phase.
Here is table for three different manufacturers’ PMT specs:
| Hitachi | Single-phase up to 167 kVA Three-phase up to 315 kVA Primary voltage up to 36 kV Secondary voltages up to 480 V Available fluids: mineral oil and ester fluids |
| Hanford | Secondary Up to and including 63 kVA Primary 100 kVA and above |
| Daelim | No-load loss: 270W Load loss 120ºC: 990W No-load current: 1.9% Pole Mounted Transformer Sizes (L X W X H): 970×880×1015 Installation size (mm): 500×820 |
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Hi……I am Kaushikee Banerjee completed my master’s in Electronics and Communications. I am an electronics enthusiast and am currently devoted to the field of Electronics and Communications. My interest lies in exploring cutting-edge technologies. I’m an enthusiastic learner and I tinker around with open-source electronics.
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