Daewoo ST Series Instruções de Operação descarregar pdf (Página 140)

5. Instability

Instability in a closed loop speed control system can be categorized into two general types.

PERIODIC appears to be sinusoidal and at a regular rate.

NON-PERIODIC is a random wandering or an occasional deviation from a steady state band

for no apparent reason

Switch C1 controls the “Lead Circuit” found. The normal position is “ON “ Move the switch to the

“OFF” position if there is fast instability in the system.

Switch C2 controls an additional circuit added is designed to eliminate fast erratic governor

behavior, caused by very soft or worn couplings in the drive train between the engine and

generator.

The normal position is “OFF”. Move to the “ON” position if fast erratic engine behavior due to a soft

coupling is experienced.

The PERIODIC type can be further classified as fast or slow instability. Fast instability is a 3Hz. or

faster irregularity of the speed and is usually a jitter Slow periodic instability is below 3Hz., can be

very slow, and is sometimes violent.

If fast instability occurs, this is typically the governor responding to engine firings.

Raising the engine speed increases the frequency of Instability and vice versa.

In this case, placing switch C1 in the “OFF” position will reduce the speed control unit’s sensitivity

to high frequency signals.

Readjust the GAIN and STABILITY for optimum control Should instability still be present, the

removal of E1 to E2 jumper may help stabilize the engine. Post locations are illustrated. Again,

readjust the GAIN and STABILITY for optimum control. Interference from powerful electrical

signals can also be the cause. Turn off the battery chargers or other electrical equipment to see if

the system disappears.

Slow instability can have many causes. Adjustment of the GAIN and STABILITY usually cures

most situations by matching the speed control unit dynamics. If this is unsuccessful, the dead time

compensation can be modified. Add a capacitor from posts E2 to E3 (negative on E2). Post

locations are illustrated. Start with 10mfds. and increase until instability is eliminated. The control

system can also

be optimized for best performance by following this procedure.

If slow instability is unaffected by this procedure, evaluate the fuel system and engine

performance. Check the fuel system linkage for binding, high friction, or poor linkage. Be sure to

check linkage during engine operation. Also look at the

engine fuel system. Irregularities with carburetion or fuel injection systems can change engine

power with a constant throttle setting Th is can result in speed deviations beyond the control of the

governor system. Adding a small amount of droop can help stabilize the system for

troubleshooting.

NON-PERIODIC instability should respond to the GAIN control. If increasing the gain reduces the

instability, then the problem is probably with the engine. Higher gain allows the governor to

respond faster and correct for disturbance. Look for engine misfirings, an erratic fuel system, or

load changes on the engine generator set voltage regulator If the throttle is slightly erratic, but

performance is fast, move switch C1 to the “OFF” position. This will tend to steady the system.

If unsuccessful in solving Instability, contact the factory for assistance.

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Daewoo ST Series Instruções de Operação Página 140

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