Cemented and enamelled wiredound resistors model PMA

These resistors are designed to obtain maximum power dissipation under optimum operating conditions.
The resistive wire is wound on a suitable ceramic support to sustain high thermal shock and is entirely covered with inorganic cement resistant to solvents. The protection offered is not only non-inflammable, but is also sufficient for normal environmental conditions. The temperature resistance of the cement is greater than the fusion temperature of the winding wire.
The connections are realised with standard collars or terminal pressure plugs (fast-on); the electric contact is guaranteed by electric spot welding.


· Standard tolerance: ± 15%
· Temperature coefficient ≤ 100 ppm/°C
· Insulation resistance > 100 Mohm (500 Vdc)
· Max operating temperature: 350 °C


For adjustable resistors it must be born in mind that the nominal power is understood as applied to the entire resistor, if only part of it is under tension, the power applied must be reduced in proportion to the part that is not used.
The nominal power Pn shown in the table refers to resistors placed horizontally and free in naturally circulating air, with an environmental temperature of 25° C.
With forced ventilation the nominal power dissipation capacity of the resistor increases as a function of the air speed.


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