# US 9,435,263 B2 · Thermal stress reduction in aircraft motor controllers

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- Number: US 9,435,263 B2
- Document ID: US9435263B2
- Status: Granted
- Kind: B2
- Application number: 14/282,273
- Filed: 2014-05-20
- Published: 2014-09-11
- Granted: 2016-09-06
- Earliest claimed: 2012-04-20
- Assignees: Hamilton Sundstrand Corporation
- Applicants: Hamilton Sundstrand Corporation
- Inventors: Huazhen Chai; Adam M. White; Mustansir Kheraluwala
- Web page: https://patentgrep.com/patent/US9435263B2

## CPC

- F02C 7/26: Starting; Ignition
- H02M 1/327: {against abnormal temperatures}
- H02M 7/487: Neutral point clamped inverters
- H02P 9/08: Control of generator circuit during starting or stopping of driving means, e.g. for initiating excitation
- F02C: GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS (construction of turbines F01D; jet-propulsion plants F02K; construction of compressors or fans F04; generating combustion products of high pressure or high velocity F23R; using gas turbines in compression refrigeration plants F25B11/00)
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

A thermal stress reduction method includes ramping an electric power generator to start an aircraft engine, for a time period associated with the aircraft engine start sequence toggling a three-level inverter switch array to a three-level pulse width modulation mode, determining if a first time interval in the three-level pulse width modulation mode exceeded a predetermined three-level pulse width modulation mode interval, in response to the first time interval exceeding the three-level pulse width modulation mode interval, toggling the three-level inverter switch array to a two-level pulse width modulation mode, determining if a second time interval in the two-level pulse width modulation mode exceeded a predetermined two-level pulse width modulation mode interval and in response to the second time interval exceeding the two-level pulse width modulation mode interval, toggling the three-level inverter switch array to the three-level pulse width modulation mode.

## Claims

### Claim 1

A thermal stress reduction method for an aircraft motor controller having a three-level inverter switch array, and configured to control an electric power generator coupled to an aircraft engine, the method comprising:
ramping the electric power generator to start the aircraft engine; and
during a time period associated with an aircraft engine start sequence, applying a current profile to the current from the electric power generator to the aircraft engine, the current profile controlling the current to reduce the thermal dissipation in the three-level inverter switch; toggling the three-level inverter switch array to a three-level pulse width modulation (PWM) mode; determining if a first time interval in the three-level PWM mode exceeds a predetermined three-level PWM mode interval; toggling the three-level inverter switch array to a two-level PWM mode, in response to the first time interval exceeding the three-level PWM mode interval; determining if a second time interval in the two-level PWM mode exceeds a predetermined two-level PWM mode interval; and toggling the three-level inverter switch array to the three-level PWM mode, in response to the second time interval exceeding the two-level PWM mode interval;
wherein the three-level inverter switch array includes a first switch, a second switch, a third switch and a fourth switch, wherein the first switch, the second switch, the third switch and the fourth switch are configured in a serial arrangement,
the array including: a three-level PWM mode that includes alternating between switching on the first switch and the third switch while applying a PWM signal to the second switch and the fourth switch, and switching on the second switch and the fourth switch while applying a PWM signal to the first switch and the third switch,
a two-level PWM mode includes turning on the first switch and the fourth switch while applying a PWM signal to the second switch and the third switch, and
a carrier frequency in the two-level PWM mode is greater than a carrier frequency in the three-level PWM mode.

### Claim 2 (depends on 1)

The method as claimed in claim 1 further comprising adjusting the current profile is to control a current magnitude per unit time.

### Claim 3 (depends on 1)

The method as claimed in claim 1 further comprising adjusting the current profile according to an exponential curve.

### Claim 4

An engine start system, comprising:
an electric power generator having a three-level inverter switch arra3˜;
an aircraft engine coupled to the electric power generator;
an aircraft motor controller coupled to the electric power generator,
wherein the motor controller configured for:
ramp the electric power generator to start the aircraft engine; and
during a time period associated with the aircraft engine start sequence, applying a current profile to the current from the electric power generator to the aircraft engine, the current profile controlling the current to reduce the thermal dissipation in the three-level inverter switch; toggling the three-level inverter switch array to a three-level pulse width modulation (PWM) mode; determining if a first time interval in the three-level PWM mode exceeds a predetermined three-level PWM mode interval; toggling the three-level inverter switch array to a two-level PWM mode, in response to the first time interval exceeding the three-level PWM mode interval; determining if a second time interval in the two-level PWM mode exceeds a predetermined two-level PWM mode interval; and toggling the three-level inverter switch array to the three-level PWM mode, in response to the second time interval exceeding the two-level PWM mode interval;
wherein the three-level inverter switch array includes a first switch, a second switch, a third switch and a fourth switch wherein the first switch, the second switch, the third switch and the fourth switch are configured in a serial arrangement
the array including: a three-level PWM mode includes alternating between switching on the first switch and the third switch while applying a PWM signal to the second switch and the fourth switch, and switching on the second switch and the fourth switch while applying a PWM signal to the first switch and the third switch,
a two-level PWM mode includes turning on the first switch and the fourth switch while applying a PWM signal to the second switch and the third switch, and
a carrier frequency in the two-level PWM mode is greater than a carrier frequency in the three-level PWM mode.

### Claim 5 (depends on 4)

The system as claimed in claim 4 wherein the current profile is adjusted to control a current magnitude per unit time.

### Claim 6 (depends on 4)

The system as claimed in claim 4 wherein the current profile is an exponential curve.