The application area of our products is the electronic applied to power whose function is , among others,  to manage and control the electric power flow supplying tension and current in an optimal way to load devices such as electric motors

A few examples are the devices and circuits deputed to the conversion of the electric tension from alternated to continuous mode (AC-DC) and vice versa (DC-AC), or to the level control of the DC voltage, to the frequency variation, to the supply of  the DC motors, to the speed control of an AC motor , to the brace control of a DC motor.

Together with the diode valves rectifiers, SCR, IT GIVES, TRIAC, IGBT, GTO, transistors and condensers there are the power resistors: they can be found in nearly all the electric circuits.

The power resistors in the electric circuits can have different purposes, such as:

• As braking resistors (both inner or external) especially in the inverters used to command brushless motors. The inverter are generally used before asynchronous electric motors.
• In the harmonic filters: in the power systems  the harmonicas are introduced in non-linear load presence. The national agencies therefore impose relative maximum distortion levels in the area of the connections. The main relative effects coming from the presence of the harmonicas are: additional overheating of the devices, acoustic noise and vibrations of the distribution system, over dimensioning of all the power connections.
• In the EMC filters: type LCR low-pass filter are used in compliance to the EU directives about electromagnetic compatibility (placed for example on the output of devices like the inverters).
  This situations is determined by the electromagnetic pulses generated by the work of the devices. The frequencies and the harmonicas produced can reach values over 100 Mhz.
• In the LCR filters for devices aimed to limit the current peaks avoiding additional loss, heat production and to limit the tension gradients.
• Pre-load (or unload) resistors in the pre-load (or unload) circuits  of the locals power source modules.
• As Resistors in the snubber nets , that are made connecting in series the condensers and the resistances in order to limit abrupt tension variations.
• As neutral grounding resistors in order to limit the breakdown current and to make them compatible with the  protection devices.
• As starter or adjuster resistances for the continuous supply motors limiting the current to the cue and varying the speed once the regimen is reached.
• As starter rotoric resistances in the wired asynchronous motors.
• As statoric resistances for low power motors.
• As anti-condensate resistors in switchboards.
• As load bank resistors for laboratory test loads.
• As heating resistors in the circuits of the conditioning systems.

The resistances are not undifferentiated: the most suitable resistance has to be selected upon the application it will be involved in.

For the development of new products the information that Fairfild needs to have are:

• the area of application
• electrical datas (tension, current, resistance, power, insulation tension, dielectric rigidity)
• usage datas (continuous, pulsive – energy to be dissipated, type and characteristics of the impulses – like duty cycle, tension and current peak).
• mechanical datas (middle axis', weight, dimensions and eventual ties)
• thermal datas (ambient temperature, maximum temperature allowed to the resistive element)
• required IP protection degree
• vibration cycles

These datas are very important for the production process in order to convey our products a lasting  durability and reliability.
One instance, for example, is the guarantee of perfect insulation and its uniformity. There actually can be a high tension in the coil due to the maximum applied tension, or a non uniform sollicitation due to the interaction between inductance, resistance and coil.
It's also fundamental that the mechanical solicitation deriving from the electrical and magnetic field is specifically reduced and contrasted. This kind of sollicitation tends to weaken the time durability of the insulation causing perforations.
It is clear that out team has to know all the details provided by the customer in order to:

• guarantee a high tension of insulation between the coils
• guarantee a low inductance in the windings
• provide a goo heat dispersion in the coils
• have a correct dimensioning go the wire