270 Volt DC system with transient suppressor

• US 5,245,500 A
• Filed: 10/28/1991
• Issued: 09/14/1993
• Est. Priority Date: 10/28/1991
• Status: Expired due to Term

• Current Assignee: Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Rozman, Gregory I.
• Primary Examiner(s): DEBOER, TODD
• Application Number:
  US07/783,508
• Time in Patent Office: 687 Days
• Field of Search: 361/56, 361/57, 361/79, 361/86, 361/87, 361/91, 361/111, 361/92
• US Class Current: 361/56
• CPC Class Codes: H02H 7/067 on occurrence of a load dump control on sudden change of load H02P9/10
• CPC Class Codes: H02H 9/04 responsive to excess voltage lightning arrestors H01C7/12, H01C8/04, H01G9/18, H01T

Abstract

The problem of noise and undesirable oscillations on a DC bus (46) are minimized using a transient suppressor (50) in connection with a 270 volt DC power system (10). The power system (10) includes an excited generator (17) developing AC power rectified to power the DC bus (46) for connection to loads (36). The transient suppressor (50) comprises a resistor (52) and a switch (54) connecting the resistor (52) across the DC bus (46). A control (60) senses bus voltage and load current and controls the switch (54) in response thereto. Indeed, the switch (54) is controlled in one of two modes of operation. The first mode comprises voltage control in which the switch (54) is turned on with a single pulse to reduce over voltage conditions, without introducing EMI noise. The second mode comprises pulse width modulating the switch (54) under low current conditions to reduce low frequency oscillations on the DC bus (46).

Claims

1. In an electrical supply having a power source with two terminals for supplying a normal operating voltage and a normal operating current to a load, a transient suppressor comprising:

voltage sensing means which senses voltage across the two terminals;

current sensing means which senses current drawn by a load connected to the terminals;

a resistor and a switch connecting the resistor across the terminals; and

a control connected to said voltage sensing means, said current sensing means and said switch and including means for controlling said switch in one of two modes of operation, a first mode comprising turning the switch on in response to said voltage exceeding said normal operating voltage as sensed by said voltage sensing means and a second mode comprising turning the switch on in response to said current being below said normal operating current as sensed by said current sensing means.

2. The transient suppressor of claim 1 wherein said first mode of operation comprises turning the switch on when sensed voltage exceeds a first reference value and turning the switch off when the sensed voltage is below a second reference value.

3. The transient suppressor of claim 1 wherein said second mode comprises modulating said switch when sensed current is below a reference value.

4. The transient suppressor of claim 3 wherein said second mode comprises pulse width modulating said switch at a select duty cycle.

5. The transient suppressor of claim 1 wherein said control further comprises a timeout protection circuit including means for determining a length of time the switch is turned on and timeout means for turning off the switch if the length of time exceeds a desired amount.

6. The transient suppressor of claim 5 wherein said timeout protection circuit further includes means for determining a length of time the switch is turned off and said timeout means enables turning on the switch when the turn off time exceeds a desired amount relative to the turn on time.

7. The transient suppressor of claim 6 wherein said timeout means comprises a counter having a count value incremented at a first rate if said switch is turned on and decremented at a second rate if the switch is turned off.

8. The transient suppressor of claim 7 wherein said first rate is higher than said second rate.