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DE3

CIRCUIT BREAKERS

Motor Circuit Protectors

H-, J-, and L-Frame MCP Selection

Adjustable Instantaneous trip circuit breakers are

intended for use in combination with motor starters

with overload relays for the protection of motor circuits

from short circuits. Other specific applications include

rectifiers and resistance welders. These C/B’s contain

a magnetic trip element in each pole with the trip point

adjustable from the front. Interrupting ratings are

determined by testing the instantaneous trip C/B in

combination with a contactor and overload relay.

Refer to C.E.C. 28-210.

Select instantaneous trip C/B’s as follows:

1. This selection table is suitable for motors with

Loc

ked-Rotor Indicating Code Letters as follows;

Horsepower Motor Code Letters

1/2 or less A-L

3/4 to 1 1/2 A-K

2to3 A-J

5to25 A-H

30 to 125 A-G

150 or more A-F

For other motors order a special thermal-magnetic cir-

cuit breaker with magnetic trip settings for the specific

motor

specify motor horsepower, voltage, frequency,

full load current and code letter or locked rotor cur-

rent.

2. Determine motor HP rating from the motor name-

plate.

3. Refer to the table at right and select an instanta-

neous trip C/B with an ampere rating recommended

the HP and voltage involved.

4. Select an adjustable trip setting of at least 700%,

not to exceed 1300%, of the motor full load amperes.

(FLA).

5. The 1300% maximum setting may be inadequate

instantaneous trip circuit breakers to withstand

current surges typical of the magnetization current of

auto-transformer type reduced voltage starters, or

open transition wye-delta starters during transfer from

“start” to “run”, constant HP multi-speed motors, and

motors labeled “high efficiency”. Select thermal-mag-

netic circuit breakers from page DE3-5 for those appli-

cations.

6. Part-winding motors, should have two circuit break-

ers selected from the above at not more than one half

the

allo

wable trip setting for the horsepower rating.

The two circuit breakers should operate simulta-

neously as a disconnecting means.

7. Motor full load currents, 1/2 HP thru 200 HP are

tak

from Table 44 of the C.E.C. & Table 430-150 of

the NEC. Above 200 HP from UL 98, Table 18.2.

Select wire and circuit breakers on basis of horse-

power rather than nameplate full load current for Gen-

eral Motor Applications. Do

not

use these values to

select overload relay thermal units. See Book

CP2 for selection of thermal units when actual full

load is not known. The voltages listed are rated

motor voltages. Corresponding nominal system volt-

ages are 200 to 208, 220 to 240, 440 to 480 and 550

600

volts.

Adjustable Instantaneous Trip Circuit Breakers For Single Motor Circuit Protection

Based on 1990 CEC Section 28-210 & Table 44, and 1990 NEC Article 430-52 and

Table 430-150.

HP Ratings of Induction Type Full Standard

Squirrel-Cage and Load MAG-GARD® Magnetic Trip

Wound Rotor Motors Amps. Circuit Breaker Settingsc

Three Phase 60 Hz ac

(Note7) a Catalogue No. b

200 230 460 575

LO HI

Volts Volts Volts Volts

10 14 H( )L36030M38X

500% 1300%

5 15..2 H( )L36030M38X

15 17 H( )L36030M38X

5 17.5 H( )L36030M38X

15 21 H( )L36030M38X

7-1/2 20 22 H( )L36030M38X

7-1/2 25.3 H( )L36030M38X

20 25 27 H( )L36050M38X

10 28 H( )L36050M38X

30 32 H( )L36050M38X

10 32.2 H( )L36050M38X

25 34 H( )L36050M38X

30 40 H( )L36050M38X

40 41 H( )L36050M38X

15 42 H( )L36050M38X

15 48.3 H( )L36100M38X

40 50 52 H( )L36100M38X

20 54 H( )L36100M38X

20 60 62 H( )L36100M38X

50 65 H( )L36100M38X

75 221 L( )L36400M38X

200 240 L( )L36400M38X

250 242 L( )L36400M38X

100 248 L( )L36400M38X

100 285 L( )L36400M38X

300 289 L( )L36400M38X

250 302 L( )L36400M38X

125 312 L( )L36400M38X

350 336 L( )L36400M38X

125 359 L( )L36600M38X

150 360 L( )L36600M38X

300 361 L( )L36600M38X

400 382 L( )L36600M38X

150 350 414 L( )L36600M38X

500 472 L( )L36600M38X

400 477 L( )L36600M38X

200 480 L( )L36600M38X

a Motor full-load currents are taken from NEC Table 430.150. Select wire and circuit

breakers on basis of horsepower rather than nameplate full-load current per NEC

430.6 (A) for general motor applications. Do not use these values to select overload

relay thermal units. The voltages listed are rated motor voltages. Corresponding

nominal system voltages are 200–208, 220–240, 440–480 and 550–600 V.

b To complete catalog number, replace the blank with the appropriate rating (G, J, or

L). M38X is for standard trip units. For advanced trip units (LCD display, metering

and communication, replace with M58X).

c Only MIN and MAX settings are shown, intermediate settings are available on all

circuit breakers.

d See NEC 430.52(A) for circuit breaker settings above 800%.

e If due to motor starting characteristics, trip settings at the 1300% maximum permitted

level are needed, the next size Mag-Gard circuit breaker should be chosen.

Class 680

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