Q1) what are instrument transformer?

If we want to measure extremely high values of current and voltage than there are two ways of measuring it. One is to use high capacity instruments which would be obviously costly. Another way is to use the transformation property of current and voltage.

Current and voltage can be stepped down by using a transformer whose turn’s ratio is known and then measuring the stepped down current and voltage by a normal ammeter or voltmeter. The original magnitude can be determined by multiplying the stepped down magnitude with the turn’s ratio. Such specially constructed transformer with accurate turn’s ratio are called as instrument transformer. There are two types of instrument transformer:

1) Current transformer

2) Potential transformer.

Q2) what are current transformers?

Current transformer are put in series with the line in which the current is to be measured. They are used to step down the current to such a level so that it can easily be measured by using an ammeter. Generally they are expressed as primary: secondary current ratio for e.g.: A 100:5 amp CT will have primary current of 100 Amp’s and secondary current of 5 Amp’s.

Standard secondary rating of CT’s are either 5 or 1 Amp’s

Common application of CT available in market is “clamp meter”.

Q3) what are potential transformer?

Potential transformers are also known as voltage transformers and they are basically step down transformers with extremely accurate turn’s ratio. Potential transformers step down the voltage of high magnitude to a lower voltage which can be measured with standard measuring instrument. These transformers have large number of primary turns and smaller number of secondary turns.

A potential transformer is typically expressed in primary to secondary voltage ratio. For example, a 600:120 PT would mean the voltage across secondary is 120 volts when primary voltage is 600 volts.

Q4) what are the differences between current and power transformer?

At basic level, they are no different. Both of them work on the principle of electromagnetic induction. But the difference lies in their usage.

Current transformers, which come under the category of Instrument transformers, are mainly used along with other instruments for the purpose of measurement. As with every other instrument that is used for measurement purpose on electrical circuits, a current transformers must have a very low impedance in order to not affect the current in the circuit it is measuring by a huge amount. Also it is very important to ensure that the phase difference between primary and secondary currents is as close to zero as possible. A current transformer also has very few, or even a single turn on primary and many on secondary.

Power transformers on other hand are used to transfer power from primary side to secondary side. Here the emphasis is not that much on reducing the impedance in transformer, nor is it much on reducing phase angle error close to zero. Here emphasis is laid more on efficiency than accuracy. Secondly, a power transformer has way too many turns on its primary, than a single turn, although it’s still lesser than those on secondary.

Q5) Which machine can produce current and potential transformer? 

There have two technologies to cast epoxy resin current transformer the old one and traditional one is by vacuum casting tank,called vacuum casting technology,The second latest technology is APG (automatic pressure gelation ) technology ,the casting machine is APG clamping machine,also called APG machine,epoxy resin apg machine,Now APG machine is first choice of users.because below advantages:

1.Production Efficiency，Take produce 10KV CT as example,you can get a qualified CT within 30 mins。
2.Investment，The price of APG machine about 55000-68000USD
3.Installation，only need connect electric,then can run machine
4.Electrical Performance,partial discharge，Chemical resistance, electrical insulation, strength resistance are greatly improved,we have testing equipments in company.
5.Automation Degree:There only need 1-2 workers operate the machine, the efficiency is greatly raised but the intensity of labor is decreased.just need control keys on power cabinet.
6.Operation,It’s easy operate APG machine, our engineer will show how to operate it and we also have user manual to guide operate our machine, no need pay high salary to hire professional engineers to operate machine.

you could go to our youtube channel, to see the operation videos of this machine

https://www.youtube.com/watch?v=2HkHCTPBR9A