Month: August 2017

Measuring Transformers

The main purpose of transformers is to reduce high voltages or electrical currents in electric energy transmission and distribution networks, particularly for the purposes of measuring them or for safe detection of devices with reduced dimensions and high accuracy.

As an example of the use of this type of transformers, it is possible to stand out the equipment of measurement of the voltage, current and electrical power in networks of energy, the phasimeters, the frequencímetros and the relays of protection, the counters of electrical energy, the insertion of signals High frequency transmission lines, namely for communication between power plants, substations and the telecontage of the energy consumed by users.

Two basic types of measurement transformers can be found. The voltage is intended to ensure the reduction of the high voltages present in the lines, allowing their routing to the places frequented by operators and their reading in common voltmeters. The other type is the current one, which makes it possible to carry out the main functions of the process of measuring electrical quantities of high absolute value, ensuring the galvanic isolation between the high voltage or current network and the measuring circuit.


The induction electric motor has a torque equal to zero at synchronous speed. As the load increases, the engine speed can gradually decrease gradually until it reaches a point where the torque can reach the maximum value the engine can achieve in a normal rotation.

If the load torque is increased, the motor rotation may fall abruptly and severely, and may cause the rotor to catch, possibly causing damage.

The basic conjugate consists of the conjugate calculated as a function of the power as well as the synchronous speed. The nominal or full load torque is the torque developed by the motor at rated power, at rated voltage and frequency.

industrial control transformer TP533123S

The conjugate with locked rotor or starting torque or starting torque is the minimum torque obtained by the locked motor, for all angular positions of the rotor, under rated voltage and frequency. This conjugate can be expressed in Nm or even in percentage of the nominal conjugate.

Briefly, the locked rotor conjugate needs to be as high as possible, so that the rotor can overcome the initial inertia of the load, achieving rapid acceleration.

Transformers – Scott Connection

The Scott connection allows the transformation of three-phase systems into biphasic or tetraphasic systems and vice versa. In it, two special transformers of the same ratio are used: one with a central tap and an equilibrium transformer whose tap configuration will depend on the intended mode of operation.

We have the way of obtaining a three-phase two-phase system from a balanced three-phase system, with the phasor diagram of voltages for the primary (three-phase) side and the secondary (biphasic) side, respectively. In this configuration the balance transformer should have a tap corresponding to 86.6% of the total nominal voltage of the main transformer SKF-Bearing SIKAC 16.

In order to achieve a four-phase system, it is enough to make some changes in the secondary connections and this system is nothing more than a biphasic system with 5 wires, composed of 4 phases + neutral, where each of the line voltages is 90 ° out of phase, , The phase difference between the adjacent phase voltages.

In this configuration, the secondary ones of the single-phase transformers are connected from their central taps, and at this point a neutral conductor is connected which will serve each of the four phases.