Figure 2-36.-Type AQB-LF250 complete circuit breaker, front view.

AQB-LF250 (fig. 2-36), combines the standard AQB

circuit breaker and a current-limiting fuse unit. This

fuse unit interrupts the circuit when the current is in

excess of the interrupting rating of the breaker.

Constructed as one compact unit, the AQB-LF circuit

breaker incorporates the current-limiting fuses (fig.

2-37) as integral parts of the circuit breaker. The

common trip features and trip units in this type of

circuit breaker are identical to those in the AQB-A250

circuit breakers.

The current-limiting fuse unit is designed so that

it trips the breaker and opens all poles if any

current-limiting fuse (fig. 2-38) is blown. After a fuse

has blown, the circuit breaker cannot be reclosed until

the blown fuse is replaced. Any attempt to remove the

fuse unit when the circuit breaker is in the closed

position will automatically trip the breaker.

The AQB-LF250 circuit breaker is inter-

changeable with the AQB-250 circuit breaker, except

a larger cutout is required in the switchboard front

panel to accommodate the fuse unit of the

Figure 2-36.-Type AQB-LF250 complete circuit breaker,

front view.

AQB-LF250.

Figure 2-37.--Type AQB-LF250 complete circuit breaker, front view with fuse unit removed.

2-26