Method and apparatus for sensing load current in a motor controller
US5874818A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 11, 1997 |
| Grant date | Feb 23, 1999 |
| Priority date | — |
| Expiry date | Jun 11, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02M7/5395
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
The approach to measuring load current in a multi-phase bridge inverter circuit connected to a multiphase load involves placing a single current sense resistor in series with the inverter circuit and power supply. The current flow through the sense resistor is sampled during a portion of the switching cycle wherein the inverter is configured to enable current flowing through the multi-phase load to flow through the sense resistor. Typically, this will occur during a portion of the switching cycle (e.g. PWM cycle) wherein the load is being actively driven. For a 120.degree., 3-phase, 6-step commutation sequence typically used to control a d.c. brushless servo motor, the sampled current is a time-multiplexed measure of the current flow through each load phase. The same sense resistor is also used for indicating a short circuit condition by comparing the voltage across the resistor to a reference voltage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.