Instability - KIRLOSKAR DV Series O & M Manual

As an aid to help reduce the levels of EMI of a conductive nature, a battery line filter and shielded cables
are conveniently supplied by GAC in KT130. To reduce the levels of EMI of a radiated nature, a shielded
container P/N CA114 can be sourced from GAC and its distributors.
In severe high energy interference locations such as when the governor system is directly in the field of a
powerful transmitting source, the shielding may require to be a special EMI class shielding. For these
conditions, contact GAC application engineering for specific recommendations.

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 in the ESD5500. 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 in the ESD5500 that 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 3 Hz. or faster
irregularity of the speed and is usually a jitter. Slow periodic instability is below 3 Hz., 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 in Diagram 1. 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 in
Diagram 1. Start with 10 mfds. 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. This 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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