MB30-CS datasheet(13/105 Pages) MITSUBISHI

13 / 105 page

Total

clearing

time

Latching

(relay)

time

Electromagnet

oparating

time

Time for

contacts to

open

Arc-

extinguishing

time

Mechanical

delay

time

Arcing

time

Fig. 4.3 Instantaneous Tripping Sequence

4.3 Effects of Mounting Attitudes

Instantaneous tripping is negligibly affected by mount-

ing attitude, for all types of MCCB. Delay tripping is

also negligibly affected in the thermal types, but in

the hydraulic-magnetic types the core-weight effect

becomes a factor. Fig. 4.4 shows the effect, for verti-

cal-surface mounting and for two styles of horizontal-

surface mounting.

(vertical plane)

100%

93%

90%

110%

93%

107%

100%

Fig. 4.5 Effects of Nonvertical-Plane Mounting on Current

Rating

4.4 DC Tripping Characteristics of AC-Rated MCCBs

Table 4.2 DC Tripping Characteristics

Trip unit

Thermal

magnetic

Hydraulic

magnetic

Long delay

No effect below 630A

frame. Above this, AC

types cannot be used

for DC.

DC minimum-trip

values are 110~140%

of AC values.

Instantaneous

DC inst.-trip current is

approx. 130% of AC

value.

Tripping curve

Overcurrent

4.5 Frequency Characteristics

At commercial frequencies the characteristics of

Mitsubishi MCCBs of below 630A frame size are vir-

tually constant at both 50Hz and 60Hz (except for the

E Line models, the characteristics of MCCBs of 800A

frame and above vary due to the CT used with the

delay element).

At high frequencies (e.g., 400Hz), both the current

capacity and delay tripping curves will be reduced by

skin effect and increased iron losses.

Performance reduction will differ for different types;

at 400Hz it will become 80% of the rating in breakers

of maximum rated current for the frame size, and 90%

of the rating in breakers of half of the maximum rating

for the frame size.

The instantaneous trip current will gradually in-

crease with frequency, due to reverse excitation by

eddy currents. The rise rate is not consistent, but

around 400Hz it becomes about twice the value at

60Hz. Mitsubishi makes available MCCBs especially

designed for 400Hz use. Apart from operating char-

acteristics they are identical to standard MCCBs (S

Line).

Floor-mounted

Overcurrent

Ceiling-mounted

Wall-mounted

(horiz. or vert. attitude)

Fig. 4.4 Effect of Mounting Attitude on the Hydraulic-

Magnetic MCCB Tripping Curves

MB30-CS Datasheet(PDF) 13 Page - Mitsubishi Electric Semiconductor

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