Method and apparatus for preventing excessive heat generation in a alternator of a generator set

• US 6,701,221 B1
• Filed: 10/24/2000
• Issued: 03/02/2004
• Est. Priority Date: 10/24/2000
• Status: Active Grant

• Current Assignee: Kohler Company
• Original Assignee: Kohler Company
• Inventors: Van Maaren, Richard D., Eaton, Zane C., Dorn, Douglas W., Kaura, Vikram
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): Bahta, Kidest
• Application Number:
  US09/695,166
• Time in Patent Office: 1,225 Days
• Field of Search: 700/236, 700/293, 700/287, 700/292, 700/290, 361/319, 361/68, 361/31, 290/40
• US Class Current: 700/286
• CPC Class Codes: H02P 9/006 Means for protecting the generator by using control H02H7/06 takes precedence; control effected upon generator excitation circuit to reduce harmful effects of overloads or transients H02P9/10

Abstract

A method and apparatus are disclosed for preventing damage to an alternator of a genset resulting from high currents within the alternator. The method includes calculating, at a processor, a first quantity related to a current flowing through the alternator during a first time period, and comparing, at the processor, the first quantity with a first threshold. The method further includes calculating, at the processor, a second quantity related to the current flowing through the alternator during at least one of the first time period and a second time period, and comparing, at the processor, the second quantity with a second threshold. The method additionally includes indicating a current overload condition if at least one of the first quantity exceeds the first threshold or the second quantity exceeds the second threshold.

Claims

1. A method of preventing damage to an alternator of a genset resulting from high currents within the alternator, the method comprising:

calculating, at a processor, a first quantity related to a current flowing through the alternator during a first time period;

comparing, at the processor, the first quantity with a first threshold;

calculating, at the processor, a second quantity related to the current flowing through the alternator during a second time period, wherein one of the first and second time periods is of greater length than the other of the first and second time periods;

comparing, at the processor, the second quantity with a second threshold; and

indicating a current overload condition if at least one of the first quantity exceeds the first threshold or the second quantity exceeds the second threshold.

2. A method of preventing damage to an alternator of a genset resulting from high currents within the alternator, the method comprising:

calculating, at a processor, a first quantity related to a current flowing through the alternator during a first time period;

comparing, at the processor, the first quantity with a first threshold;

calculating, at the processor, a second quantity related to the current flowing through the alternator during at least one of the first time period and a second time period;

comparing, at the processor, the second quantity with a second threshold; and

indicating a current overload condition if at least one of the first quantity exceeds the first threshold or the second quantity exceeds the second threshold,

wherein the calculating includes

(a) obtaining a first measured current value indicative of the current during a first short time period;

(b) taking the square of a first related value that is functionally dependent upon the first measured current value to obtain a first comparison value;

(c) repeating (a) and (b) to obtain at least one additional measured current value indicative of the current during at least one additional short time period, and to take the square of at least one additional related value that is functionally dependent upon the at least one additional measured current value to obtain at least one additional comparison value; and

(d) adding the first comparison value and the at least one additional comparison value to obtain at least one of the first quantity and the second quantity.

3. The method of claim 2, wherein the first time period and the second time period each include at least one time period equivalent in length to the first short time period.

4. The method of claim 2,

wherein the first related value is a first normalized current value, and

wherein the first normalized current value is calculated based upon the first measured current value by dividing the first measured current value by a maximum current value.

5. The method of claim 4, wherein the maximum current value is calculated based upon the following equation:

$I_{\mathrm{MAX}}=\frac{\mathrm{KW}\times <br><br>1000}{\mathrm{System}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Voltage}\times <br><br>\mathrm{.8}\times <br><br>\sqrt{3}};<br><br>$

and wherein the KW value is obtained by way of a maximum power subroutine and a voltage/frequency lookup table.

6. The method of claim 2,

wherein the first related value is a first normalized current value, and

wherein the first normalized current value is calculated based upon the first measured current value by dividing the first measured current value by a maximum current value and then subtracting unity.

7. The method of claim 2,

wherein the at least one additional measured current value includes nine measured current values, each of the nine measured current values being obtained based upon nine respective measurements taken during nine respective short time periods;

wherein the at least one additional comparison value includes nine comparison values, each of the nine comparison values being obtained by taking the squares of nine respective related values that are functionally dependent upon the nine respective measured current values; and

wherein the first quantity is obtained by adding the first comparison value and each of the nine comparison values.

8. The method of claim 7,

wherein the first short time period and each of the nine short time periods are successive single-second time periods, which together form a ten second window;

and

wherein the first threshold is equal to 90.

9. The method of claim 2,

wherein (a) and (b) are continually repeated for additional short time periods while the genset is operational, so that a respective additional measured current value is obtained during each respective additional short time period, a respective additional related value is obtained that is functionally dependent upon each respective additional measured current value, and a respective comparison value is obtained by taking the square of each respective additional related value.

10. The method of claim 9,

wherein the first quantity is obtained by adding the first comparison value and each of the additional comparison values.

11. The method of claim 9,

wherein the second quantity is obtained by:

(i) adding the first comparison value when the first related value is a positive number;

(ii) subtracting the first comparison value when the first related value is a negative number;

(iii)adding each respective additional comparison value when the respective related value is a positive number; and

(iv) subtracting each respective additional comparison value when the respective related value is a negative number.

12. The method of claim 11, wherein the first short time period and each of the additional short time periods are successive single-second time periods;

and

wherein the second threshold is equal to 40.

13. The method of claim 11, wherein the first quantity includes the first comparison value based upon the first measured current value, but the second quantity does not include the first comparison value, and does not include any comparison value based upon the first measured current value.

14. A method of preventing damage to an alternator of a genset resulting from high currents within the alternator, the method comprising:

(a) calculating a first quantity equaling a first sum of n squares of n type-A normalized currents determined based upon n most recent current measurements obtained during n most recent successive short time periods;

(b) determining whether the first quantity exceeds a first threshold;

(c) providing a first command to limit an operation of the genset when it is determined that the first quantity exceeds the first threshold;

(d) calculating a second quantity equaling a second sum of x values functionally dependent upon x squares of x type-B normalized currents determined based upon x current measurements obtained during x successive short time periods, wherein x is the total number of short time periods that have occurred since at least one of a first time at which a performance of the method began and a second time occurring after the first time;

(e) determining whether the second quantity exceeds a second threshold; and

(f) providing a second command to limit an operation of the genset when it is determined that the second quantity exceeds the second threshold.

15. The method of claim 14, further comprising:

(g) obtaining a new current measurement with respect to a new short time period; and

(h) repeating (a)-(g).

16. The method of claim 14, wherein n is equal to 10, and each short time period lasts one second.

17. The method of claim 14, wherein (a)-(c) are performed only when an engine of the genset is operating, and (f) is performed only when x exceeds 9.

18. An apparatus for preventing damage to an alternator of a genset resulting from high currents within the alternator, the apparatus comprising:

a means for measuring a current flowing within the alternator during successive time periods;

a processor coupled to the means for measuring, wherein the processor is operable to;

calculate a first parameter that is related to a first set of measured current values that were obtained at respective different times by the means for measuring during a first time period,

calculate a second parameter that is related to a second set of measured current values that were obtained at respective different times by the means for measuring during a second time period,

compare the first parameter with a first threshold and the second parameter with a second threshold, and

provide a command to cause at least a portion of the genset to be limited in its operation when either the first parameter exceeds the first threshold or the second parameter exceeds the second threshold; and

a means responsive to the command to alter the operation of the genset.

19. An apparatus for preventing damage to an alternator of a genset resulting from high currents within the alternator, the apparatus comprising:

a means for determining whether a current flowing through the alternator during a recent time period has been excessive;

a means for determining whether a current flowing through the alternator during an extended time period different in length than the recent time period has been excessive; and

a means for halting the operation of the genset if at least one of the two determining means determines that the current has been excessive.