May 20, 2021 Current Transformer
Current Transformer is a type of “instrument transformer” that is designed to produce an alternating current in its secondary winding which is proportional to the current being measured in its primary. Current transformer reduces high voltage currents to much lower value and provide a convenient way of safety monitoring the actual electrical current flowing in an AC transmission line using a standard ammeter. The principal of operation of a basic current transformer is slightly different from that of an ordinary voltage transformer.
Current transformer consists of only one or very few turns as its primary winding. This primary winding can be either a single flat turn, a coil of heavy-duty wire wrapped around the core or just a conductor or bus bar placed through a central hole as shown. Current transformer is often called “series transformer” as primary winding which never has more than a few turns, is in series with the current carrying conductor supplying a load.
The secondary winding however, may have a large number of coils turns wound on a laminated core of low-loss magnetic material. This core has a large cross-sectional area so that the magnetic flux density created is low using much smaller cross-sectional area wire, depending upon how much the current must be stepped down as it is tries to output a constant current, independent of the connected load.
The second winding will supply a current into either a short circuit, in the form of an ammeter, or into a resistive load until voltage induced in the secondary is big enough to saturate the core of cause failure from excessive voltage breakdown.
There are three type of current transformers: wound, torodial and bar.
- Wound Current Transformer - The transformers primary winding is physically connected in series with conductor that carries the measured current flowing in the circuit. The magnitude of the secondary current is dependant on the turns ratio of the transformer
- Torodial Current Transformer - These do not contain a primary winding. Instead, the line that carries the current flowing in the network is threaded through a window or hole in the torodial transformer. Some current transformers have a "split core" which allows it to be opened, installed, and cloase, without disconnecting the circuit to which they are attached.
- Bat-type Current Transformer - This type of current transformer uses the actual cable or bus-bus of the main circuit as the primary winding, which is equivalent to a single turn. They are fully insulated from the high operating voltage of the system and are usually bolted to the current carrying device.
Current transformers can reduce or "step-down" current levels from thousands of amperes down to a standard output of a known ratio to either 5 Amps or 1 Amp for normal operation. Thus, small and accurate instruments and control devices can be used with current transformers because they are insulated away from any high-voltage power lines.
Current Transformers are available through Quick Time Engineering Inc.
Quick Time Engineering Inc is an international company with offices and distribution networks in the USA, Hong Kong, Europe and Malaysia.
In its 20 years of operation since 1998, Quick Time Engineering Inc had emerged from a local engineering company with a single staff that provided solutions in factory automation to become nowadays a company that serves the Oil & Gas industries, EPC contractors, System Integrators and other industrial automation and process control companies worldwide. Customers from over 50 countries worldwide trust us with their need for process control instruments and industrial automation products.
For more information about Quick Time Engineering Inc , visit www.quicktimeonline.com or email enquiry@quicktimeonline.com
