Controller Protection Controller Protection/Timed Cutback
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MillipaK PUMP Controller Manual Page 36 07/11/05
Timed Current Cutback
During periods of high current usage the power components of the controller produce
considerable heat. Under normal circumstances the controller will cutback the maximum current
supplied to the load when the heatsink temperature rises above a safe level for the controller
components. However, when the current supplied is close to the maximum rating of the controller
the temperature rise of the components leads the heatsink temperature by up to 40°C. If this
situation was allowed to arise damage may result in the controller. In order to prevent this
situation a timed current cutback feature is incorporated in the MillipaK controller, which works
as described below:
The controller monitors the power through the armature MOSFETs during a 60 second period and
uses the average current seen over this time to determine the new current limit. The new current
limit is then calculated as shown in the table below.
New Current Limit (% of ABR) Current Limit Now
(% of ABR)
Low Power Medium Power High Power
100% 100% 80% 60%
90% 100% 80% 60%
80% 90% 70% 60%
70% 80% 70% 60%
60% 70% 60% 60%
CBR - Is the Controller Block Rating.
The system will limit the current through the motor to the calculated limit during operation.
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