Hi,
I'm after suggestions for protecting a DC permanent magnet motor.
The motor is used to drive a hydraulic swash plate pump for typically 30 min -1 hour at a time. Mostly the motor is on light load when running, but it is intermittently loaded to higher than its continuous rating, for 5 mins or so.
The failure mode is overheat of the rotor winding - but it isn't going to be easy to sense the temperature of the winding directly.
I've been thinking of:
1) putting a small value resistor in series with it and bonding a temperature sensor to that - tripping the supply if it gets too hot.2) putting a temperature sensor in the airflow from the motor's cooling fan.
3) sensing the motor current and feeding that into an integrator and setting a trip level on the integrator output.Any thoughts? The motor only has a fuse* at the moment, plus a nose to sense that it is "smelling a bit hot"..
- A fuse with the correct i2t curve would do nicely, perhaps. The present one, fitted by the system manufacturer, is a quickblow one that doesn't even blow if the motor stalls..