Load controller with digitally modeled overload protection and analog tracking of heat state during power off
US5303160A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 13, 1992 |
| Grant date | Apr 12, 1994 |
| Priority date | — |
| Expiry date | Jan 13, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H6/005
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Microprocessor based apparatus for controlling an electrical load, such as a motor, includes an external capacitor for storing an analog equivalent of a digitally modeled heat state signal, such as the I.sup.2 t characteristic of the motor. The voltage on the capacitor decays to mimic motor cooling when the microprocessor is powered down with deenergization of the motor. The stored analog signal is updated by periodically converting the analog signal to a retrieved digital heat state signal which is compared to the latest calculated value of the heat state signal. If the retrieved value is below the present calculated value, an input/output port is set to a high output state to charge up the storage capacitor. If the retrieved value is above the calculated value, the port is configured as an output port with a low state to reduce the voltage on the capacitor. When the retrieved heat state signal equals the calculated signal, the port is configured as an input port with a high impedance to maintain the stored value on the capacitor. To maintain accuracy over a wide range with an 8-bit processor, the selected limiting value of the I.sup.2 t characteristic is loaded into a large regis…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.