Automated Circuit Breaker Calibration Philip Simonin (EE) Kyle Weber (EE) Louis LeBlanc (EE) Tyler Lyon (EE) Advisor: Ali Gokirmak Sponsor: Carling Technologies Carling Contacts: Marek Szafranski, John Lach, Stephen Simonin
History Carling Technologies is headquartered in Plainville CT. Founded in 1920, Carling is established among the world's largest manufacturers of circuit breakers, switches, power distribution units, digital switching systems, and electronic controls. Engineering research and new product development is conducted in Connecticut. Manufacturing occurs at plants located in Texas, China and Mexico. The company s hydraulic circuit breakers are created with various capabilities in mind. Calibration of these breakers is required depending upon application desired current trip point.
Company Goals And Initiatives Carling Technologies wishes to become even more adept at handling the changes in industry standards. They aim to do this by researching the capability of having breakers controlled via bluetooth or wifi in the near future. This allows for automated controlled and a faster response time than manual analog circuitry. Carling Technologies is also committed to quality. This is demonstrated through evaluating, revalidation, and carefully selecting from multiple design alternatives for each project they choose to take on.
Project Basis In-lab experience showed that manual tuning of breakers was timeconsuming The effort required to calibrate these lead to the idea of creating an automated system Coincided with Carling s initiative to move forward with digital and control systems Something low level enough to safely begin prototyping (A series DC breakers, requiring low voltage and current)
A Series DC Breakers Circuit Breaker Specifications: A-Series Circuit Breakers 5, 10, 15, 20A rated breakers Max Voltage Current Rating: 80 VDC Resistance values from Line to Load Terminal Single Pole 10,000 ON/OFF operations @ 6 per min. Trip free
Objective Design and create functioning circuit calibration unit Comprised of pneumatic press, stepper motor, PSoC, load bank, relays, and other opto-driver switches Breakers of 5, 10, 15, or 20 Amperes must be brought to proper trip point Implement easy to use microcontroller
Applications Minimizes inaccuracies between products Allows engineers and technicians to test products and achieve repeatable results Allows for random testing of breakers before shipment Modifiable for other product lines Can potentially be applied to multiple pole breakers
Traditional Methods Magnetic circuit breaker calibration is traditionally achieved manually on production line Involves the doubling of rated current to bring the iron core within the dashpot of the breaker to the trip-point required This process may be repeated numerous times Small window around the desired trip current value where adjustments can be made Tripping the breaker at the necessary level requires slow adjustments around the point of tripping
Problems To Address Calibration currently done manually Introduces unwanted human error Up to +/- 30% error Effects manufacturing production rate Makes exact adjustment difficult for technicians and engineers
What is Being Calibrated? The spring attached to the actuation arm Controls magnetic flux in the plunger Alters current let-through and trip-point Adjusts spring force on actuation arm
Magnetic Core Operation Iron core brought within the dashpot of breaker Viscous silicone fluid used as damper to prevent instant tripping; this slows its journey through the container, allowing for a time delay on the trip Silicone resists the iron core from being electro-mechanically pulled through (via magnetic flux), causing actuation arm to activate and open the breaker and interrupt circuit Silicone viscosity and magnetic attributes are varied to provide specific trip points and/or time delay of tripping
PSoC PSoC 4 CY8CKIT-049 4200 C code programmable, via USB Monitors current Signals relays and stepper (bidirectional) Conducts calibration adjustments Automates system Complete in 30 seconds or less
PSoC Circuit Switch simulating breaker in position and operator ready Relay for switching between full 200% and 115% loads using high current 120VAC power relay Solenoid relay and Big Easy for motor drive (forward and reverse)
Why PSoC? Carling has been developing a system utilizing PSoC and so have extensive awareness with regard to its programming and application PSoC is the newest family of microcontroller integrated circuits by Cypress Semiconductor With a CPU core and mixed-signal arrays of configurable integrated analog and digital peripherals it offers more customizability than Arduino PSoC is extremely cost effective at $4 a development stick yet can plug and play for each different series or rated breaker
Top Design and Control Clocked PWM can be adjusted to alter speed of stepper motor ADC with follower input configuration from op-amp and protected by Zener. by Zener, looks for contact open/close Provisions for breaker in position are operator active Outputs kept at low level current and drive optocouplers and LEDs
PSoC Approximately 35 pins for I/O Data paths available Easy to program Flash use is 5120 of 32768 bytes (15.6%) SRAM use is 1500 of 4096 bytes (36.6%)
PSoC MiniProg PSoC programmer via USB 5 pin docking and programs in seconds Alternate ten pin or direct USB available
Stepper Motor Nema 11 Motor Step angle: 1.8 ± 5% (200 steps/revolution) Two Phase Bidirectional Driven by an H-Bridge Holding Torque Current / Phase Voltage / Phase Phase Resistance Phase Inductance (1KHz) 0.6 Kg*cm 0.67 A 3.8 V 5.6 Ω± 10% 4.2 mh± 20%
Pneumatic Press/Rig Pneumatic activated to contain breaker vertically (50 psi) via an air compressor Spring loaded compress for horizontal containment PSoC and control circuitry bolted next to rig Motor to be hand held rather than mounted
Power Relay Coil Voltage: 6-600V Current Max: 40A Response Time: 30 ms Average Power Dissipation: 4 W
Questions or Comments?v Why Optocoupler/Zener? A Zener Diode is used to regulate and stabilize the load voltage in the two circuits and control the voltage for input to PSoC, maintaining logic level voltages Optocouplers used in the interface between the load bank and PSoC circuits, provides low current draw for operation and galvanic isolation The key advantage it provides is the electrical isolation with high insulation resistance in the thousands of megohms, which is useful to handle high voltage differential between the two circuits
Load Bank Taps: One tap for 200% Current Another for 115% Current (active during calibration) High current relay will be made interchangeable between loads
Supply Adjustments for System The breaker circuit power supply, like all of them, is affected by loading. To avoid this, we use the following voltages for each breaker: 5A 5.04V 10A 5.11V 15A 5.18V 20A 5.26V These minor adjustments are to be considered In programming PSoC
Schematic
Breaker Test Diagram 40A
Why 200% Current? 200% current is chosen to initialize to move the iron core into position at a rate that allows for good speed without damaging the viscous fluid or the core. The solenoid is activated to prevent the trip arm from actuating, allowing the core to enter the dashpot near trip point without interrupting the current flow or tripping before calibration. After the 10 or fewer seconds have past, the 115% load is activated, and the trip point is reached via digital reading and signaling. The code is adjusted to allow for the reaching of trip point. Reverse operation is also possible if needed
Completion of Project Constructed Load Bank for testing Coding and simulation of PSoC Developed PSoC control circuit on breadboard Completed and tested motor circuit Mounted PSoC and Load circuit to prototype rig Minor adjustments necessary for breaker calibration (via code)
Future Prospects Carling will make modification to our prototype Currently, there remains a human element involved in the calibration to start and stop the software The end goal is a product capable of reliable implementation on the assembly line for automatic circuit calibration Hopes of implementing this in the near future.
Questions or Comments?