Cummins Confidential

Application Engineering Bulletin

Subject: B & C Series G-Drive Governing This AEB is for the following applications:

Automotive Industrial Power Generation Author: 80.01

Date May, 1989 Page 1 of 4 AEB Number 80.01

Engine Models included:

Fuel Systems included: The purpose of this Application Engineering Bulletin is to define the criteria for governing in Generator Drive application, and to provide guidance on the present capabilities of the B & C Series products. In addition, some alternative governing improvements are discussed. G-DRIVE GOVERNING CRITERIA G-Drive governing can be divided into two major types – “Isochronous” and “Droop”. Isochronous Governing means that there is NO speed (frequency) change between full load and no load operations of the genset. Droop governing means that there is an increase in speed as load is reduced and vice versa. Some of the confusion occurring on the subject of governing performance is the result of differences between the definitions used “engine people” and “genset people:. Genset People:

• Droop is what counts. • It is maximum allowable, not a toleranced nominal amount • It is defined as the permanent speed increase (%) from synchronous speed

(1500 or 1800) at rated power to no load.

Speed (no load) - Speed (full load) Droop = Speed (full load) x 100 Where Speed (full load) is either 1500 RPM or 1800 RPM exactly.

• It needs to be 5% or less (have heard as low as 3%)

NOTE: Transient performance relates to the dynamics of the temporary speed changes and is a separate performance issue from governor performance. Engine People:

• Regulation is what is used. • It is a toleranced nominal figure (typically +/- %). • It is defined as the speed increase (%) from the governor break point (at full power)

to some defined (15% in the case of the C) residual load. • Governor break point (up to 3% above rated speed) varies. • Full power varies from pump to pump.

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AEB 80.01 Page 2 of 4

Besides customer expectations, there are several international standards regarding genset governing performance: ISO-3046/4 (BS-5514) has the following requirements for governing: Governing Class Speed Droop A0 (highest) Isochronous A1 (high) 5 % Max. A2 (normal) 8% Max. A1 is the category required by most GOEM’s for “routine” set performance. This means that the max. high idle-no load speed (with rated load set exactly at 1500 or 1800 as appropriate) is 1575 RPM for 50 Hz. and 1890 RPM for 60 Hz. ISO-8538/5 (a draft standard at the moment) has the following requirement for governing: Performance Class Frequuency Droop G1 (general purpose lighting, etc.) 8 % Max. G2 (commercial power- lighting, pumps, fans, hoists, etc) 5 % Max G3 (telecommunications, thyrister controlled load, etc) 3 % Max. G4 (data processing equipment computers, etc.) Isochronous B & C Series Governing Capability: Testing conducted at Cummins and elsewhere indicates that the basic governing capabilities of the B & C series products are as follows: Droop (per G-Drive Criteria) Engine Model Fuel Pump 50 Hz. 60 Hz. 4B(T)3.9 & 6BT5.9 CAV “DPA” 5.5 % 5.4 % 6CT8.3 BOSCH “A” 5.5 % 5.6 % 6CTA8.3 OSCH “MW” 6.6 % 5.6 %

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AEB 80.01 Page 3 of 4 In a number of cases, the fuel pumps used o specific applications have been “fine tuned” for improved initial performance. However, these improvements require individual development programs, and often jeopardize other performance criteria such as cold starting, steady state stability, etc. In addition, these improvements are then subject to the usual effects of governor degradation with use. The CAV “DPA” fuel pump used on the B Series G-Drive engines experienced accelerated wear of many of the components in the mechanical governing system which results in loss of governor performance. “Wear out” of the governor has occurred in as little as 150 hours of operation when running on #2 diesel fuel. Other fuels such as arctic grades and military fuel (JP series) merely aggravate this premature wear out. FOR THESE REASONS, THE CAV DPA PUMP IS CONSIDERED SUITABLE ONLY FOR STANDBY POWER APPLICATIONS WHERE TIGHT GOVERNING IS NOT A REQUIREMENT, AND WHERE PARALLEL OPEERATION IS NOT SPECIFIED. The Bosch pump used on the C Series do not exhibit the extreme wear rated of the CAV pumps used on the B Series. In either case, if governing performance better than that shown on the table above is required by the application, then some form of external governor is required. In the case of the CAV pump on the B Series, an external governor is required to compensate for the extreme governor wear in prime power applications. Cummins Power Systems offers governor kits for these engines using the Barber-Colman DYNA-8000 governor: CPS KIT P. N. Engine Model 12 Volt 24 Volt 4B(T)3.9 150-2310 150-2216 6B(T)5.9 150-2311 150-2217 6CT(A)8.3 150-2312 150-2242 When an external governor is used with the CAV DPA pump, the governor spring must be changed to a “stiff” version to avoid governor interaction. In addition, CAV recommends the use of a “heavy duty” governor cover which utilizes a bushed governor shaft hole to prevent wear and subsequent fuel leakage. The CPS kits currently include the stiff spring but not the heavy duty cover since the kits were developed for Standby Power applications requiring isochronous governing.

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AEB 80.01 Page 4 of 4 PLANS FOR IMPROVEMENT: B Series: We are in the process of releasing the following governing operations on the B Series to be available fro the engine plants:

• Standard CAV DPA pump governor but highlighted as being suitable for use only on Standby applications with a note that the governing can degrade to as much as 10% in only 150 hours of operations.

• CAV DPA pump governor with heavy duty cover and stiff spring for use with an external

governor in prime power or isochronous applications.

• Factory supplied B-C DYNA 8000 governor kit including actuator, controller, linkage, and mounting hardware.

• A “dummy” option for using a customer supplied external governor. Provides a tag indicating

that the fuel pump is set up for use with a customer supplied external governor. Additional alternatives are being evaluated on the B Series aimed at eliminating the need for an external governor on non- isochronous applications. C Series: On the C Series, we have a program underway to evaluate a “hydraulic damper” which may allow the droop on the Bosch pumps to be tightened without causing instability. At the moment, the plans are to provide this as a simple retrofit (no need to remove or recalibrate the pump) for the units (particularly 50 Hz.) requiring improved governing. The evaluation of the performance of this feature is expected to be completed in the next 90 days.