All posts by Fresh Element

Types of Transformers

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Various I-Tech Transformers

There are six different types of transformers we will address in this hub and none of them will be related to a toy or a movie. Transformers are a type of passive electronic component that are used to step up or step down the voltage in a circuit or system.

The voltage transformer is similar to the more common power transformer. It is also referred to as a potential transformer and is used for metering and protection in high voltage circuits. It is designed in order to achieve an accurate voltage ratio over the range of the load and is often used to step up low voltages or to step down high ones.

The power transformer is the most commonly used transformer. One thing to remember is that a transformer does not actually create power, but transfers it from one coil winding to another. The power transformer is actually a type of voltage transformer and it is used in many different power type applications. Some of these transformers are immersed in oil in order to keep them cooler and stop them from overheating.

The current transformer is also known as a series transformer. It is often placed in series with a high current circuit. It is used for the measurement of electric circuits and they are often used in metering and protective relays.

As the name implies, the impedance transformer was designed to ensure accurate impedance transformation. For example, a transformer may be used to “match” the impedance of an amplifier to a speaker. In fact, they are often used in low-frequency amplifiers.

The Isolation transformer has no direct connection between windings, but they are connected via the magnetic flux in the core. In most cases, the winding ratio is a one to one. In other words, it is neither a step up, nor a step down but a means of isolating the circuit from the power supply.

Lastly, the auto transformer in unique in its tapped windings. The primary is normal, but the secondary has at least three taps where electrical connections can be made and these different taps result in different voltages. They are often used in applications where it is needed to interconnect systems operating at different voltages.

Oil-Filled Capacitors

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Arizona Capacitors- Oil-Filled Cap
Source: Arizona Capacitors, Inc

Oil-filled capacitors are generally high power and/or high voltage. They are often of the wound film capacitor variety and their size is usually fairly large because of the energy they can store.

The oil in the capacitor has more than one purpose. Firstly, it is used to remove any air voids and secondly it helps to cool or remove the heat away from the capacitor windings. These windings tend to generate an excessive amount of heat when they reach their discharge capacity. The oil works to offset these higher temperatures so that the capacitor can remain working optimally.

For metalized film capacitors, the oil has another benefit, in that it helps prevent arcing from between the two plates. If, however, arcing were to occur the oil would reseal the hole caused by the arcing. This is why, even though oil-filled metalized film capacitors are not a very common application, these type capacitors are often referred to as self healing capacitors.

The type of oil used is not what one would find in a automobile engine or the lawn mower sitting in the garage. Arizona Capacitors, Inc., for example, uses a mineral oil in most cases, but a silicon oil may be used as well. Both of these oils are chosen because they are non-hazardous to people and the environment, but the mineral oil is the most economical of the two.

Prior to the mid 1970’s some of the oil-filled capacitors contained PCBs (polychlorinated biphenyls). These were desirable because of their stability and low flammability. The United States Congress banned all domestic production of PCB material in 1979.

1553 Data Bus Transformers

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Raycom 1553 Data Bus Transformers

The first MIL-STD-1553 data bus specifications were published by the United States Air Force in 1973 for the F-16 Fighting Falcon. Now, however, it is used extensively by many branches of the United States military, as well as for NATO.

The “Bus” itself is a wire pair that operates with an impedance of between 60 and 85 ohms at a frequency of 1 MHz. The actual data bus transformers are used in this specification where the transmitters and receivers couple. The transformer is used in tandem with a resistor to ensure that the bus does not conduct current through the aircraft. Also, it is used to reduce any impact from a short circuit.

There are only a few transformer manufacturers that are certified to produce the MIL-STD-1553 data bus transformers. This is mainly because it is a difficult specification to meet and an even more difficult one to become certified to build. Since this is used in flight applications, quality must be the primary focus in the manufacture and testing of these parts.

Furthermore, there are only about three companies that produce a transformer that can actually interface in all the various 1553 data bus circuits. There have been some compatibility issues identified with transformers and transceivers and Raycom Electronics has redone their design to address these specific issues. It is one thing to meet a specification, but quite another to have a product that will work in all the various types of applications. Raycom Electronics, is one of these companies.

There has been discussions over the years that fiber-optics would eventually make the 1553 data bus obsolete. but time has proved this to be incorrect. One of the main reasons being that fiber-optics would be almost impossible to repair. It is more likely that RF would eventually supplant the 1553 data bus, but that appears to be very far off in the future.

EMI Filters

CS-EMI-FilterCustom Suppression EMI Filter

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EMI Filter by Custom Suppression

 

EMI filters (Electromagnetic Interference), also known as RFI filters (Radio Frequency Interference), are vital passive electronic components. Filters in general, as the name implies, are used to “filter” out the unwanted frequencies in an electronic circuit.

EMI filters are used more specifically to suppress the electromagnetic interference, which is essentially just a high frequency noise. This noise is an undesired emission that can cause the malfunctioning of a circuit or equipment. These types of EMI/RFI (interference) can be found in power supplies, microprocessors, and AC motors. This interference can be generated inside an electrical device by impedance and voltage variances in the conductors. It can also be generated outside the device via telephone lines and power cords, just to name just a few.

EMI filters can be further categorized as “Low Pass” filters. This means that they block out the high, and in this case, unwanted electromagnetic frequencies and allow only the lower frequencies to pass through.

Two of the most important components of an EMI filter are inductors and capacitors. They are critical in the reduction of the interferences that are being suppressed. The capacitors that are used are referred to as shunting capacitors because they feed the current in a specific range into the inductors that reduce the voltage as the pass through.

The EMI filter reduces the EMI or RFI by restricting the flow of high frequency signals thereby attenuating the unwanted signal strength. Without these critical components certain circuits wound be unable to function properly, making EMI/RFI filters a vital part of many electronic circuits.