MB30-CS datasheet(97/105 Pages) MITSUBISHI

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8.1.2 Low Temperature Application

In conditions where temperatures reach as low as

–5˚C special MCCBs are usually required. Mitsubishi,

however, have tested their standard MCCBs to tem-

peratures as low as –10

°C without any detrimental

effects.

For conditions where temperatures drop below

–10˚C special MCCBs must be used.

If standard MCCBs experience a sudden change

from high temperature, high humidity conditions to low

temperature conditions, there is a possibility of ice

forming inside the mechanism. In such conditions we

recommend that some form of heating be made avail-

able to prevent mal-operation.

In conditions of low temperature MCCBs should

be stored in either the tripped or OFF position.

Low Temperature MCCBs

Special low temperature MCCBs are available that

can withstand conditions where temperatures fall to

as low as –40˚C. These special MCCBs are available

in sizes up to 1200A in the standard series and above

50A in the compact series.

8.1.3 High Humidity

In conditions of high humidity the insulation resistance

to earth will be reduced as will the electrical life.

For applications where the relative humidity ex-

ceeds 85% the MCCB must be specially prepared or

special enclosures used. Special preparation includes

plating all metal parts to avoid corrosion and special

painting of insulating parts to avoid the build up of

mildew.

There are two degrees of tropicalisation:

Treatment 1- painting of insulating material to avoid

build up of mildew plus special plating

of metal parts to avoid corrosion.

Treatment 2- painting of insulating material to avoid

build up of mildew only.

8.1.4 Corrosive Atmospheres

In the environment containing much corrosive gas, it

is advisable to use MCCB of added corrosion resis-

tive specifications.

For the breakers of added corrosionproof type,

corrosion-proof plating is applied to the metal parts.

Where concentration of corrosive gas exceeds the

level stated below, it is necessary to use MCCB of

added corrosion resistive type being enclosed in a

water-proof type enclosure or in any enclosure of pro-

tective structure.

Allowable containment for corrosive gas.

H2S

0.01ppm SO2

0.05ppm

NH3

1ppm

8.1.5 Affecting of Altitude

When MCCBs are used at altitudes exceeding 2000m

above sea level, the effects of a drop in pressure and

drop in temperature will affect the operating perfor-

mance of the MCCBs. At an altitude of 2200m, the air

pressure will drop to 80% and it drops to 50% at

5500m, however interrupting capacity is unaffected.

The derating factors that are applicable for high alti-

tude applications are shown in table 8.3. (According

to ANS

I C 37.29-1970)

Table 8.3 Derating Factors for High Altitude Appli-

cations

Altitude

3000m

4000m

5000m

6000m

Rated current

0.98

0.96

0.94

0.92

Rated voltage

0.91

0.82

0.73

0.65

For example: NF800-SEP on 4000m

1. Voltage

The rated operating voltage is AC690V. You should

derate by 690x0.82=565.8V. It means that you can

use this NF800-SEP up to AC565.8V rated voltage.

2. Current

The rated current is 800A. You should derate by

800x0.96=768A. It means that you can use this

NF800-SEP up to 768A rated current.

8.2 Vibration-Withstand Characteristics

8.2.1 The Condition of Test

1. Installation position and Direction of vibration

• Every vertical and horizontal at vertical installed

(as shown in Fig. 8.1)

2. The position of MCCBs and vibration time

Forty minutes in each position (ON, OFF and TRIP)

3. Vibration criteria

• Frequency

5~100Hz

• Vibration acceleration

2.2g

• Period

10min./cycle

8.2.2 The Result of Test

The samples must show no damage and no change

of operating characteristic (200% release), and must

not be tripped or switched off by the vibration.

Vertical

Wire

connection

Horizontal

Fig. 8.1 Applied Vibration

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