Transformers

TRANSFORMERS INCREASE THE EFFICIENCY OF POWER TRANSMISSION.

Lamps, motors, etc., are designed to be used on a low voltage partly for the sake of safety. However, power is never transmitted any great distance at a low voltage due to large power losses in the line, or because of heavy investments in copper wire. To overcome these difficulties, one transformer is used to step up the voltage for the transmission line and another is used to reduce the voltage to the desired value at the point of consumption. Even when large amounts of power are to be transmitted for a moderate distance, transformers are generally used.

THE BASIC TRANSFORMER PRINCIPLE.

A simple transformer may consist of two coils placed on an iron core. When an alternating current is supplied to one coil (called the primary), a magnetic field is produced. The magnetic field varies with the input voltage, coupling to the second coil (called the secondary) and inducing a voltage in it. Since the same magnetic field couples both primary and secondary, the voltage induced per turn in each winding is the same. Further, since the induced voltage in an ideal coil equals the supplied voltage, it follows that the voltage per turn on the primary equals the voltage per turn on the secondary.

Thus, the voltage of a winding is proportional to the number of turns. If we wish to increase a voltage 10 times, it is necessary to use a transformer with 10 times as many turns on the secondary as on the primary. A similar transformer "turned around" at the other end of the line will step down the voltage to the original value.

These are the most basic types of transformers used in industry today. They are also known as linear transformers. They provide electrical "isolation" between the primary and secondary windings. Normally they have a primary with more than one secondary winding. They reduce electrical noise between primary and secondary. Electrostatic shielding can be added to further increase isolation. These can be designed in single phase or three phase.

 Step-up/Step-down Transformers are used to change the incoming voltage. They either increase it (step-up) or decrease it (step-down). They are often designed to do both to accommodate worldwide voltage requirements in a single transformer unit.

Nicollet has manufactured single phase units from 25VA to 20KVA and three phase units from 50VA to 75KVA.

Nicollet builds to custom electrical requirements and does not compete with "Off the Shelf" or standard catalog items.

Control Transformers are used primarily for step-down to power low voltage circuits and/or accessories. These are commonly used in many types of industrial equipment. Nicollet can build these units from 25VA on up. Control Transformers are used primarily for step-down to power low voltage circuits and/or accessories. These are commonly used in many types of industrial equipment. Nicollet can build these units from 25VA on up.

Inverter Transformers closely resemble pulse and wideband transformers because their proper function depends on the input switching circuitry used. This circuitry typically applies a non-sinusoidal waveform that is reflected at the output. Input waveshape, switching frequency and voltage are the minimum information required for design. Any size over 100VA can be manufactured. Inverter Transformers closely resemble pulse and wideband transformers because their proper function depends on the input switching circuitry used. This circuitry typically applies a non-sinusoidal waveform that is reflected at the output. Input waveshape, switching frequency and voltage are the minimum information required for design. Any size over 100VA can be manufactured.

Rectifier Transformers are used to step-up or step-down ac voltages for rectification and filtering. Input voltage and frequency establishes the primary rating while the secondary ac voltages and currents are determined by the dc requirements. Nicollet can manufacture single phase units from 25VA to 20KVA and three phase units from 50VA to 75KVA. Rectifier Transformers are used to step-up or step-down ac voltages for rectification and filtering. Input voltage and frequency establishes the primary rating while the secondary ac voltages and currents are determined by the dc requirements. Nicollet can manufacture single phase units from 25VA to 20KVA and three phase units from 50VA to 75KVA.

Like isolation transformers, autotransformers are used to step-up or step-down voltages. However, autotransformers have only one winding and therefore no electrical isolation from input to output. The advantage of using an auto wound transformer over an isolation transformer is that they are smaller, lighter and less expensive. Typical applications include motors, heaters and other non-sensitive load requirements. Nicollet can build these from 100VA to 40KVA single phase and three phase units to 75KVA.

 Standard output ferros are typically used as voltage regulating rectifier transformers. The ferroresonant transformer produces a square output waveform, ideal for rectification in direct current circuits. This type is used primarily in brute force applications where no additional circuitry is required. Nicollet can manufacture units from 25 VA to 15KVA in 50HZ, 60HZ, or 50/60HZ.

 Sine wave ferros use a harmonically compensated secondary winding, producing a waveform that is nearly sinusoidal. They are used principally to protect critical loads from power surges or utility problems. This type can replace multi-tap input transformers in this kind of circuit. These products can be manufactured in sizes from l00VA to l5KVA single phase in 50HZ or 60HZ.

 Ferroresonant inverter transformers are found primarily in uninterruptible power supplies. The ferro takes a low voltage pulsed square wave generated by an inverter and battery source and converts this to line voltage with a sine wave or square wave output. Nicollet can design and build this product in a range from l00VA to l5KVA. 50HZ or 60HZ.

 Current Limiting Transformers

This type of transformer limits the output current during an overload condition by reducing the output voltage. In fact the output voltage can be designed to drop to zero volts when a short circuit occurs (without damaging the transformer). Current limiting transformers are commonly used to provide protection in high voltage circuits but can be used in low voltage applications as well, generally from 10VA to 1000VA.

 Chokes

Chokes, also known as inductors, are commonly used in inverter, power supplies, UPS, welders, variable speed drives, and motor starters.

Filter chokes are used to filter electric circuits. They are often used with capacitors to reduce ripple in DC applications. It is common practice to design filter chokes with an air gap in the core to prevent dc saturation. The air gap, size of the core and number of turns depend on the inductance desired, direct current in the winding and the ac voltage across the winding. Sizes available are typically two pounds and larger. Filter chokes are used to filter electric circuits. They are often used with capacitors to reduce ripple in DC applications. It is common practice to design filter chokes with an air gap in the core to prevent dc saturation. The air gap, size of the core and number of turns depend on the inductance desired, direct current in the winding and the ac voltage across the winding. Sizes available are typically two pounds and larger.

Swinging chokes are filter chokes designed with two inductance ratings at two current levels. In swinging chokes the core is purposely allowed to saturate at higher values of direct current and are non-linear. They are characterized by smaller air gaps, more turns and larger size. Sizes available are typically two pounds and larger. Swinging chokes are filter chokes designed with two inductance ratings at two current levels. In swinging chokes the core is purposely allowed to saturate at higher values of direct current and are non-linear. They are characterized by smaller air gaps, more turns and larger size. Sizes available are typically two pounds and larger.

AC chokes are also referred to as AC reactors. They are primarily used to limit current in applications where temporary overloads and short circuits must be accommodated without damage. The reactor will have a nominal rms current rating and a maximum current rating. The rms rating is based on the duty cycle of the maximum and the normal operating current. Sizes available are typically two pounds and larger. AC chokes are also referred to as AC reactors. They are primarily used to limit current in applications where temporary overloads and short circuits must be accommodated without damage. The reactor will have a nominal rms current rating and a maximum current rating. The rms rating is based on the duty cycle of the maximum and the normal operating current. Sizes available are typically two pounds and larger.