FLYWHEEL 3N3804 - Caterpillar

Figure 2-4. Recommended Terminal Shaft Travel
Figure 2-5. Non-linear LinkageNon-linear Linkage
Applications involving a butterfly valve, such as a gas engine, require a non-linear linkage.Figure 2-5 illustrates the relationship between governor output shaft and butterfly valve obtained with simple linkage of maximum non-linearity. When installing this linkage, make sure the two following conditions are attained when the linkage is in the no-load position: 1. The lever which is attached to the governor output and the connecting link are in line with the governor output shaft and the point of attachment of the connecting link to the butterfly lever.2. The butterfly lever is at 90° with the connecting link.Refer to the engine manufacturer's instructions for the correct linkage selection and installation.Speed Adjustment
There are several types of speed adjustments available for the PSG.Lever
Some governors have a lever attached to the external end of the speed-adjusting shaft. This lever is used in conjunction with the high- and low-speed stop screws. Using a linkage arrangement with the lever provides a remote speed adjustment for the governor. The screw in the cover is used to set the minimum-speed stop while the screw in the case controls the maximum-speed stop of the governor. The speed-setting shaft does not usually extend from governors designed for pneumatic or motor speed setting.Pneumatic Head or Motor
The governor can be equipped with either a pneumatic speed-adjustment head or an electric motor for remote speed adjustment (see Chapter 6 for details about these two types of speed setting). Both of these speed setting systems use a high-speed stop screw.Constant Speed
Some PSGs are equipped with a speed-setting screw in the cover. This is the same screw used as the minimum-speed stop with speed-setting devices.Speed Droop
PSG droop is internally or externally adjustable between zero and seven percent. Speed droop, a reduction in speed setting as fuel increases, is expressed as a percentage of the difference between the lower full-load speed and the high speed at no load. Speed droop permits load division between two or more engines driving generators in parallel or connected to a single shaft. If the engine is operated alone or on a dc system with proper generator compounding, the governor may be set for zero droop (isochronous operation). Negative droop (governor speed setting increases as load increases) must not be set into the PSG governor. The governor will not provide acceptable control with negative droop. If the governor output shaft does not use the full 2/3 of available travel from NO LOAD to FULL LOAD, droop will be reduced proportionately.For ac generating units tied in with other units, set the droop sufficiently high to prevent interchange of load between units. If one unit in the plant or system has enough capacity, set its governor on zero droop and it will regulate the frequency of the entire system. This unit then takes all load changes within the limits of its capacity and control the frequency if its capacity is not exceeded.All units may be run in droop, but the no load