Start circuit for electric starting of engines

Details Start circuit for electric starting of engines Start circuit for electric starting of engines

1999-09-07

2001-07-10

Casaregola, Louis J. (Department: 3746)

Power plants

Combustion products used as motive fluid

Different fluids

C244S05300R, C318S441000

Reexamination Certificate

active

06256977

ABSTRACT:

TECHNICAL FIELD
This invention relates generally to circuits for controlling starting current to a motor, and particularly to a circuit for controlling starting current to a starter for a gas turbine engine as well as a method for starting such engines.
BACKGROUND OF THE INVENTION
An auxiliary power unit, (APU), is a type of gas turbine engine which is commonly mounted in aircraft and performs a number of different functions. These functions include providing secondary power to the aircraft as well as providing pressurized bleed air for main engine starting and the aircraft's environmental control system. Typically, APUs are started by a DC starter motor which is mounted on the APUs gearbox.
Referring to
FIG. 1
which shows a prior art start circuit
10
, electric starting of APUs in airplanes is often accomplished by providing DC power from two distinct sources in parallel. One source is an onboard APU battery
12
and the other source is DC power derived from AC generators through a transformer-rectifier unit
14
, (TRU). When an APU start is initiated, commands from the aircraft control system close contactor
16
and starting current from the APU battery
12
and TRU
14
combine at junction
20
and then flow to the APU starter motor
26
provided contactors
2
and
24
are closed.
The operation of the circuit
10
is controlled by the APUs electronic control box, (ECB)
28
. When the ECB
28
receives a command
50
from the aircraft to start the APU, it sends a close signal to contactors
22
and
24
. Voltage sensors
32
,
34
, and
36
provide voltage signals to the ECB
28
.
A disadvantage to this prior art circuit
10
, is that when both the battery
12
and TRU
14
are operating, the combined inrush current is more than required to accelerate the APU. This occurs because the system is typically sized for battery only starting to assure that the APU can be started when the TRU is not operating. That is, for example, when the aircraft is on the ground and the main engines are shut down. Because the starter motor
26
is typically a series wound device, the combined power produces high inrush current at the inception of a start. This high inrush current can cause excessive heating of the starter motor, reduced life of the contactors, and reduced life of the APU gearbox due to the initial high impact torque generated by the starter motor.
Accordingly, there exists a need for a start circuit used in the electric starting of an APU aboard an aircraft that can mitigate high inrush current when starting power is being provided from a battery and TRU in parallel.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a start circuit for electric starting of an onboard APU that mitigates high inrush current.
Another object of the present invention is to provide a start system that incorporates the start circuit contemplated by the present invention.
Another object of the present invention is to provide a method for starting an APU.
The present invention achieves these objects by providing a start circuit controlled by an electronic control box for providing power from one or both of a battery and TRU in parallel to a starter motor coupled to a gas turbine engine. The circuit includes contactors between the TRU and battery and a junction where the current from the TRU and battery combine. The circuit further includes two additional contactors in series between the junction and the starter motor. Voltage sensors and contactor position sensors are employed for diagnostics.
A novel method of starting the engine using the start circuit contemplated by the present invention is also descibed. In this method, the start is initiated with power only from the battery. After a period of time power from the TRU is added. By delaying the power from the TRU, high inrush current is avoided.
These and other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed description of a preferred embodiment of the invention when read in conjunction with the accompanying drawings.


REFERENCES:
patent: 1989958 (1935-02-01), Waters
patent: 3858391 (1975-01-01), Davis et al.
patent: 3937974 (1976-02-01), Lafuze
patent: 4456830 (1984-06-01), Cronin
patent: 4494372 (1985-01-01), Cronin
patent: 4682095 (1987-07-01), Shibata et al.
patent: 4896637 (1990-01-01), Yamamoto
patent: 5055764 (1991-10-01), Rozman et al.
patent: 5172543 (1992-12-01), White
patent: 5281905 (1994-01-01), Dhyanchand et al.
patent: 5442272 (1995-08-01), Schwartz
patent: 5451854 (1995-09-01), Uskoski
patent: 5844384 (1998-12-01), Hamm et al.
patent: 5899411 (1999-05-01), Latos
patent: 0 911 515 A1 (1999-04-01), None

Affiliated with

Also associated with

Rating

Start circuit for electric starting of engines does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Start circuit for electric starting of engines, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Start circuit for electric starting of engines will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2438500