pismorat
1/2 ton status
I have 40 amp relays that trigger the fans, but 30 amp fuses are inline, going from the 12v hot wire to the relays.
CK5
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Alternator can't cut it after Windstar fans
- Thread starter pismorat
- Start date
I disagree, since this fan is most likely a permanent magnet type. The current is a function of only the speed, voltage and internal resistance. There is no field current or phase advance in these simple motors. The load affects current mainly by slowing the motor down (the back-EMF decreases with speed, while the source voltage stays the same, so more current is driven through the coil resistance.) So as you lower the voltage, the current through the motor is lower.
The high current draw must have been pulling the voltage down and now that you've improved the electrical system you can get more current through that fuse. Are you using automotive-type blade fuses or some kind of glass fuse? For a fan motor you need one that is "slo blo" since the starting current is very high. To get a fast-acting fuse rated high enough to survive the starting current would be too high to properly protect the wiring and motor.
Hmm, quite sure you are correct.
Given the horsepower requirements to drive a big fan, I had assumed that it would be either a shunt wound also called a shunt field brush type DC motor, or a brushless AC motor which is what everybody is going to these days.
But, given the rare earth magnets available these days, PM motors can get truly powerful.
And, even in the case of the brushless motor, I'm not sure of the voltage/current relationship.
Since its more or less a standard three phase motor, you would expect it to behave like one. However, since its being run off DC through a controller, the voltage/current relationship is whatever the programmers say it is.
I know when working with AC controllers, I can program whatever current gets delivered to the motor at different speeds.
Given the horsepower requirements to drive a big fan, I had assumed that it would be either a shunt wound also called a shunt field brush type DC motor, or a brushless AC motor which is what everybody is going to these days.
But, given the rare earth magnets available these days, PM motors can get truly powerful.
And, even in the case of the brushless motor, I'm not sure of the voltage/current relationship.
Since its more or less a standard three phase motor, you would expect it to behave like one. However, since its being run off DC through a controller, the voltage/current relationship is whatever the programmers say it is.
I know when working with AC controllers, I can program whatever current gets delivered to the motor at different speeds.
pismorat
1/2 ton status
I ended up going with a 40 amp fuse for the larger motored fan and that did it. It was requiring more amps to start off. I've run it on and off for a good amount of time now and have had no issues with anything getting hot. Down the road I may go to self-resetting circuit breakers, but for now this seems like the simple and solid fix. Thanks for all the help!
