Difference between revisions of "I²t protection"
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*[http://www.copleycontrols.com/motion/pdf/IsqT.pdf Copley Controls explanation of I²t method] | *[http://www.copleycontrols.com/motion/pdf/IsqT.pdf Copley Controls explanation of I²t method] | ||
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Revision as of 12:19, 3 May 2012
I²t protection is a motor overload protection method based on motor thermal modeling. I²t is a kind of sensorless motor over temperature protection.
Protection mechanism
Motor heat generation is typically dominated by resistive heat dissipation. The heat dissipation of resistance is proportional to flowing current in power of two. I²t algorithm assumes resistive dissipation being the only heat source of motor which is good enough estimate to prevent motor burning.
I²t protection continuously estimates how much motor is dissipating heat compared to its rated heat dissipation. At 100% of rated current, heat dissipation is at maximum sustainable level. Care need to be taken only when driving more current than rated current.
I²t algorithm will simply limit output current to rated current level if algorithm calculates that motor temperature is already at maximum. If calculated temperature is below maximum, then higher (peak) currents are allowed.
Parameters
When configuring I²t protection, only one GDtool parameter needs to be set:
- Motor time constant
- Time in seconds how long it takes motor temperature rise to 63% from idle temperature to maximum allowed temperature when motor is driven continuously with 100% of rated current. If unsure, use low values (<500 seconds) to have error in safe direction.
