Motor peak and continuous current limits
All GD motor drives feature a two stage current limit in order to protect motor and drive from overheating damage.
Descroption of operation
The basic parameters for current limiting are:
- MMC Motor maximum current a.k.a. motor peak current
- MCC Motor continuous current a.k.a. motor continuous current
- MTC Motor thermal constant time
- Peak current time limit T, normally a fixed value of 1 or 2 seconds depending on drive model
In ideal case drive would output the demanded current always. However due to the fact that motor and drive generates more heat when current is higher, it is necessary sometimes to reduce output current to a safe level.
- Drive outputs demanded current infinitely if demand is below MCC level
- Drive outputs demanded current if demand is below MMC and time limit T has not been exceeded
- Drive reduces T based on thermal time constant (MTC) if calculated motor temperature is already at maximum safe level
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