Micro-Ohm Resistors - Attention to Usage of Ultra High Voltage Ceramic Power Resistors

	product guide

ATTENTION to USAGE for Ultra High Voltage Ceramic Power Resistors

To obtain optimum performanc of our resistors, the following deserves full attention.

Overall Attention

(a)

Reduction Ratio of Rated Power:

In applications where the ambient temperature exceeds 25 °C or the resistor is exposed to thermal radiation, the rated power must be reduced to be within the derating curve.

(b)

Application with Impulse Voltage, Transient Voltage, Intermittent Overload or pulse Load: Under such conditions, Designing based on the stationary state or average electric power alone must be disregarded.

(c)

Handling:

The resistor is made of ceramic. Attention must be paid not to inadverently drop or hit the ceramic resistors

Attention to Respective Resistors:

(a)

CE type:

For long time use, keep the surface temperature of the resistor at 100 °C maximum. The CE type has a tendency to increase in resistance.

Resistance value 10K

or higher when used at high voltage will drop in resistance due to the influence of voltage coefficient. (see Fig.6)

Resistor of 100

or lower used at high voltage may generate sparks at the electrode. This can be corrected by altering the electrode structure. Please contact us.

(b)

GS type:

GS type will not tolerate surge voltage, and cannot be used with impulse voltage exceeding the specifications.

If the resistor is water cooled, the water quality must be checked. Pure water is recommended.

The surface is coated with glass film to maintain the characteristics at a surface temperature as high as 300°C or higher. However, the dielectric strength will decrease at this temperature.

(c)

DC type:

DC type is not suitable for continous load. Good for short term load only.

(d)

RH type:

When used as charge or discharge resistor, reduce voltage by means of voltage reduction ratio in consideration of time constant.

Compared with CE Type, RH type has smaller injection energy capacity due to the nature of film resistors.

RH type is inductive due to the helical-cutting design of film resistor for higher resistance.

VOLTAGE REDUCTION RATIO with IMPULSE WAVEFORM:

Withstand voltage will change with time constant or wave tail duration on the basis of the standard impulse voltage. Fig. 1 represents the withstanding voltage reduction ratio versus time with 1.2 x 50 µ s waveform is defined as 100%.

POWER DERATING with PARALLEL RESISTORS COMBINED TOGETHER:

CE, GS & RH resistors, when used in parallel, will radiate heat between each other. The reduction ratio shown in Fig. 2 is to be noted.