Things to Know About a Power Transformer
by Sanju Only
[Feb 12, 2011]
Basically, a transformer is an electrical device designed to transfer alternating current or voltage from one electric circuit to another by means of electromagnetic induction. The transformer can be designed to step up or step down voltages. The transformers usually have a long and trouble free life since they do not involve any moving parts and is completely static solid state device and work under normal conditions.
The basic model or the simplest type of custom transformers consists of two or more coils of insulated wire wound on a laminated steel core. When voltage is induced to the primary coil, it magnetizes the iron core. In another coil called as the secondary coil the voltage is then induced. This is called as the output coil. The turn ratios of the primary and secondary coils determine the change of voltage between the two coils. They are capable of providing a whole range of voltage sources from the one input coil by using separate windings on the secondary side. Thus the transformers turn out to be the best method for supplying complete systems with all of their voltage requirements from one source.
If you are planning to buy a transformer, three factors should be considered prior to the purchase. You must determine primary voltage and frequency, the required secondary voltage and the capacity required in volt amperes. There is a simple process used to determine the factors. You have to multiply the load current (amperes) by the load voltage for single phase. For example if the load is 40 amperes like in a motor, and the secondary voltage is 240 volts, then 240 multiplied by 40 will give 9600 VA.A 10 KVA (10,000 volt-amperes) transformer is required.
It is better suggested to select the transformer larger than the actual load. This would allow expansion and is meant for safety purposes. If it is 3 phase KVA multiply rated volts x load amps x 1.73 (square root of 3) then divide by 1000. If you are going to design the power distribution for an entire building, then you must select the service transformer and distribution transformer.
It is also important to determine the incoming electric transformers voltage. 50 Hz, 60Hz and 400 Hz are the three common frequencies available. For high powered applications like aerospace technologies, the 400 Hz is reserved. When evaluating transformers, it is also important to consider the secondary power specifications. There are some other specifications that have to be kept in mind while selecting an electric transformer include the maximum ratings of secondary current and voltage rating, power and output rating. According to phase an connections, the power transformers have various configurations. Single phase and three-phase are most commonly used ones. Depending upon the number of primary windings in proportion, both the sizes and expense of electric transformers would increase.
You must also take essential care in the maintenance of the custom transformers. If the transformer has to be located at harsh environments, whether indoors or outdoors; it is important that the core/coil, leads, and accessories should be adequately protected.