Powell PowlVac ARG 4 Series, Instruction Bulletin

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Equipment Description

01.4IB.50023A

PowlVac® Electrically Operated 15kV Ground and Test  

per Long Island Railroad Specifications

The hinges of the three grounding contacts are 

connected together by a ground bus  

(Figure 3, d)

, which is in turn connected to a 

heavy duty ground connection located on 

the rear of the ground and test device frame 

between the center and right phases.  This 

ground connection duplicates the ground 

connection on the PowlVac

®

 circuit breaker and 

connects to the ground bus in the switchgear 

compartment, providing a path to ground from 

the ground making switch.

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The lower front cover has cutouts and 

apertures giving access to various operating 

and levering-in mechanism indicating and 

operating functions.  Removal of the holding 

screws allows the removal of the upper portion 

of the front cover and the test port shutter 

assembly, giving access to the mechanism 

and its interlocks 

(Figure 3)

, auxiliary switches 

(Figure 3, c)

, charging motor 

(Figure 4, a)

, and 

motor cutoff switch 

(Figure 4, c)

.

The ground making switch is closed and 

opened by a stored energy mechanism  

(Figure 3)

 in which a gear motor is used to 

compress a closing spring.  During a closing 

operation, the energy stored in the spring 

is used to close the ground making switch 

contacts, charge the opening springs and 

overcome friction forces.  When the ground 

making switch is opened, the energy stored 

in the opening spring and the kickoff springs 

will open the contacts.  Since the ground 

making switch has no interrupting rating, 

contact speed while opening is not important.  

The motor, located on the inside of the lower 

front cover at the left 

(Figure 4, a)

 is supported 

from the lower front cover.  Its output shaft 

is screwed to a coupler which insert into the 

eccentric drive shaft.  This shaft is supported 

in the needle bearings in the mechanism 

frame side sheets and transmits the motor 

torque from the left to the right side of the 

mechanism.

When the motor is energized, the eccentric 

shaft rotates and causes the driving arm links 

to pivot about the camshaft 

(Figure 3, l)

.  The 

drive pawl located on the links engages with 

the ratchet wheel and rotates it.  The ratchet 

wheel is prevented from rotating backwards 

by a holding pawl, which is supported on links 

which project upwards from the camshaft.

To ensure correct synchronization of the drive 

and hold pawls, the hold pawl links are located 

by a threaded shaft which passes through 

the lower front cover to the right of the 

mechanism.  The position of the holding pawls 

is adjusted by a nut on the outer end of this 

shaft.

As the ratchet wheel is rotated, projections 

from its side faces will engage drive plates 

attached to the camshaft and the camshaft will 

rotate.  Attached to the ends of the camshaft 

are crank arms and pointing outward from 

these are crank pins.  These engage with the 

front ends of the connecting rods  

(Figure 4, d)

, the rear ends of which engage in 

pins projecting from the spring compression 

plate which straddles the main closing spring.  

As the camshaft rotates, the connecting rods 

pull the spring compression plate forward, 

compressing the closing spring.

The ratchet wheel will drive the camshaft so 

that the connecting rods go forward as far as 

possible and then start to move to the rear.  At 

a certain point, the spring force will overcome 

friction and resistance and start to rotate the 

camshaft.  At the same time, the pawls are 

uncoupled from the ratchet wheel and the 

motor cutoff switch is operated.