FAQ-Step Up/Step Down Transformer

Q: What is a transformer?
A: A transformer is a device that step up or step down the voltage in an AC circuit. It converts the voltage of any value into the voltage value we need at the same frequency to meet the requirements for the delivery, distribution and use of electrical energy. For example, the electricity generated by the power plant has a low voltage level, and the voltage must be raised to be transported to a remote power consumption area. And the power supply area must be turned down to a suitable voltage level to supply power equipment and daily power equipment.

Q: What is an autotransformer?
A: An autotransformer is a transformer with only one winding. When used as a step-down transformer, a part of the winding is extracted from the winding as a secondary winding. When used as a step-up transformer, the applied voltage is only applied to the winding-partial line. on. Usually, the part of the winding that belongs to both the primary and secondary is called the common winding, and the rest of the autotransformer is called the series winding.

Q: What is an isolation transformer?
A: An isolation transformer refers to a transformer whose input windings and output windings are electrically isolated from each other, so as to avoid the danger of accidentally touching charged bodies (or metal parts that may be charged due to insulation damage) and the ground at the same time. Isolation transformers are generally (but not all) 1:1 transformers. Because the secondary is not connected to the earth, there is no potential difference between any secondary wire and the earth, it is safe to use. It has the function to step up or srep down 3 phase/ single phase power at a high voltage or low voltage as requirement.

Q: How does a transformer change voltage?
A: The transformer is made according to electromagnetic induction. It consists of an iron core made of silicon steel (or silicon steel) and two sets of coils wound around the core. The core and the coil are insulated from each other. The coil connected to the transformer and the power supply side is called the primary coil, and the coil connected to the transformer and the electrical equipment is called the secondary coil.

When the primary coil of a transformer is connected to an ac power supply, a changing line of magnetic force is produced in the core. Since the secondary coil is wound on the same iron core, the magnetic force wirecuts the secondary coil, and the induced electromotive force is inevitably generated on the secondary coil, resulting in voltage at both ends of the coil. Since the lines of magnetic force are alternating, so is the voltage of the secondary coil. And the frequency is exactly the same as the power frequency.

The theory proves that the voltage ratio between the primary coil and the secondary coil and the ratio of the turns between the primary coil and the secondary coil are related, which can be expressed as follows: the primary coil voltage / the secondary coil voltage = the primary coil turns / the the secondary coil turns. The more turns, the higher the voltage. Therefore, it can be seen that the secondary coil is less than the primary coil, which is the step-down transformer. On the contrary, is the step-up transformer.

Q: Can a transformer rated at 60Hz operate on a 50Hz service?
A: A transformer designed for 60Hz cannot operate on a 50Hz service as more losses will occur and lead to higher temperature rise and shorter life span. On the contrary, a transformer rated 50Hz can operate on a 60Hz service. ATO step up & step down transformers are designed for 50/60Hz operations.

Q: What is the voltage change rate of transformer?
A: Voltage change rate of transformer is one of the main performance indexes of transformer. When the transformer supplies power to the load, the voltage at the load end of the transformer will inevitably decrease. Comparing the reduced voltage value with the rated voltage value, the percentage is the rate of voltage change, which can be expressed by formula. The voltage change rate = [(secondary rated voltage - load terminal voltage) / secondary rated voltage] × 100%. The normal power transformer, when connected to the rated load, has a voltage change rate of 4 to 6%.

Q: What are the losses of transformers in operation?
A: The losses in transformer operation include two parts:

(1) When the coil is electrified, the eddy current and hysteresis losses in the core are caused by the alternating magnetic lines, which are collectively called iron losses.

(2) When the primary coil and the secondary coil of the transformer pass through the current caused by the resistance of the coil itself, there will be a loss of electric energy, which is called copper loss. The sum of iron loss and copper loss is transformer loss, which is related to transformer capacity, voltage and equipment utilization.

Therefore, when choosing transformer, we should try our best to make the capacity of equipment consistent with the actual usage, so as to improve the utilization ratio of equipment, and pay attention not to make the transformer run lightly.

Q: How to choose the reasonable capacity of transformer?
A: Firstly, it is necessary to investigate the power supply voltage, the actual load of users and the conditions of the places where they are used. Then, according to the technical data marked by the transformer nameplate, the transformer should be selected one by one. Generally, the capacity, voltage, current and environmental conditions of the transformer should be considered comprehensively. In normal operation, the transformer should bear about 75-90% of the rated capacity of the transformer.

At the same time, the selection of transformer should determine the primary coil voltage value of transformer according to line power supply, and the secondary coil voltage value should be selected according to electrical equipment. It is better to choose low-voltage three-phase four-wire system for power supply. When choosing the current, we should pay attention to that the load can meet the requirements of the motor when it starts (because the starting current of the motor is 4-7 times larger than that when it sinks).