Dual microprocessor electronic trip unit for a circuit interrupter

• US 6,167,329 A
• Filed: 04/06/1998
• Issued: 12/26/2000
• Est. Priority Date: 04/06/1998
• Status: Expired due to Term

• Current Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Saletta, Gary Francis, Johnson, Richard Arthur, Engel, Joseph Charles
• Primary Examiner(s): Grant, William
• Assistant Examiner(s): Bahta, Kidest
• Application Number:
  US09/055,522
• Time in Patent Office: 995 Days
• Field of Search: 700/21, 700/79, 700/78, 700/293, 700/292, 714/48, 361/97, 361/66, 361/64, 361/68
• US Class Current: 361/93.2
• CPC Class Codes: H01H 2011/0068 measuring the temperature of the switch or parts thereof
• CPC Class Codes: H01H 2071/006 Provisions for user interfaces for electrical protection devices
• CPC Class Codes: H02H 3/05 with means for increasing reliability, e.g. redundancy arrangements for logic circuits H03K19/003
• CPC Class Codes: H02H 3/0935 the timing being determined by numerical means
• CPC Class Codes: H02H 7/261 involving signal transmission between at least two stations transmission of signals in general H02H1/0061

Abstract

An electronic trip unit having two microprocessors one of which monitors the load voltage and current within the normal operating range and performs the metering and delayed trip algorithms associated with that range. A second microprocessor monitors the load current for excursions outside the normal operating range and processes those algorithms and functions associated with the instantaneous and overcurrent trip protection modes of the trip unit. Each microprocessor receives inputs representative of the monitored current that are scaled to a different factor corresponding to the range the microprocessors are assigned to monitor. In one embodiment the electronic trip unit is controlled by a master controller and in turn controls a number of accessory devices, wherein one of the microprocessors is a slave to the master controller network and the other microprocessor is a master to the accessory slave network. The microprocessors communicate with each other and either one can trip the circuit on detection of a fault condition.

Claims

1. An electronic trip unit having a first microprocessor which monitors a load current and is responsive to a given state of the load current to initiate a signal to open the load current circuit, including a second microprocessor for monitoring a characteristic of the load current in its normal operating range;

wherein the monitored values of the load inputted to the first and second microprocessors are scaled to different levels; and

wherein the signal inputted to the second microprocessor is scaled so that the microprocessor input signal representative of the peak value of the load current within its normal operating range is maintained slightly below the saturation level of the second microprocessor'"'"'s processing circuitry.

2. A method of monitoring a circuit to perform protection and metering functions of an electronic trip unit employing a plurality of microprocessors comprising the steps of:

performing the metering and voltage based protection functions of the electronic trip unit with a first of the plurality of microprocessors;

performing instantaneous and overcurrent trip components of the protection functions of the electronic trip unit with a second of the plurality of microprocessors; and

wherein the first and second microprocessors monitor current in a load including the step of scaling the current to each microprocessors to a different value corresponding to the range of values monitored by said first and second microprocessors, respectively, which is established by the function performed respectively by each said first and second microprocessors.