Cyclone electric motor - Did I kill it?

Discussion in 'Electric Bicycles' started by lookingelectric, Oct 28, 2007.

  1. I have a cyclone motor that I usually run with a couple of 28V batteries in parallel. The person who had it before me ran it at 56V, so I tried moving some of the batteries into a series configuration so that I could produce more power. I took this on a steep hill and the motor went off partway up the hill.

    I put the system back into the 28V configuration, gave it an hour to cool down and tried it again. The motor gave a little jerk and then stopped.

    Did I kill my motor? Or is it something else?
     

  2. beast775

    beast775 Guest

    voltage

    im thinkin a bad connection somewhere,which configuration did you set up in.ie 3 series 2 parallel?e motors wont bolt if there fried.more info on your config battery setup.;)
     
  3. mickey

    mickey Guest

    I'd suspect the controller rather than the motor. Can you remove the sprocket and straight wire the motor to a lesser voltage to see if it will spin?
     
  4. billvon

    billvon Guest

    Note that this will work ONLY with brushed DC motors. It will not work with brushless motors. If you connect a brushless DC motor to DC power directly, it will jerk a bit and then "lock up." But it probably won't damage anything as long as you limit the current.

    (Cyclone makes both brushed and brushless motors, so check your manual!)
     
  5. mickey

    mickey Guest

    Do brushless motors require the controller to spin then? Good to know. Thanks.
     
  6. billvon

    billvon Guest

    Basically yes.

    Brushed DC motors have magnets on the outside (stationary) and coils on the inside (spinning.) The motor works by creating an electromagnet out of the rotating coils such that it is attracted to the magnets on the outside.

    Once the electromagnet lines up with the magnet, though, motion stops. That's not that useful, so a system called a commutator is used so that the electromagnet's field is always at an angle to the magnet's field. Once the fields get close to lining up (which would stop the motor) the commutator turns off that electromagnet and turns on the next farthest away one.

    In regular motors, this is done with brushes and commutator rings; the brushes are constantly connecting and disconnecting the various electromagnets as the core rotates. That's why you often see sparks when you look inside a regular DC motor. The sparks come from the circuit being opened and closed while current is flowing.

    This is also why you can just hook one of these motors up to a battery and see it spin. All the "work" of switching the coils happens inside the motor.

    Brushless DC motors do things backwards. In a brushless DC, the magnet spins and the electromagnet coils are on the outer (stationary) part of the motor. Since there are no spinning electromagnets to help with commutation, it must be done externally. So for brushless DC motors, an external controller switches the power on and off to the outside electromagnets to keep that magic angle between the electromagnetic field and the magnetic field. The good thing there is that there are no brushes to spark and wear out, and only one moving part within the motor (the magnet) to deal with.
     
    Last edited by a moderator: Oct 29, 2007
  7. ibdennyak

    ibdennyak Guest

    how brushless motors work

    Hey, thanks for the explanation. I knew how brushed DC motors work, but wasn't sure of the function of the controller in the brushless setup. Recently had problems with my hub motor setup, which turned out to be corroded connections, and a non waterproof plug, (constant rain here lately) but some automotive water resistant ;) plugs, and renewal of my soldering skills seems to have solved that, at least temporarily. Now a question. I run about 20 mph with 48 volts (speedo on the way) but the specs on the controller and motor claim they are good to 60 volts. What do you think? (I may be old, but I ain't dead yet) Thanks

    Denny
     
  8. billvon

    billvon Guest

    That's a tough question to answer. Here are a few things that go into it:

    1) Motors don't care much about voltage unless we're into the hundreds of volts; that's where insulation starts to break down. Motors DO care about current, though, and higher voltages can push more current through a winding. Too much current is a bad thing; it overheats the motor. Brushless motors are more immune to this than most other motors (there are just so few parts) but with enough heat you can cook the bearings or even damage the magnets.

    2) Brushless controllers, alas, do care quite a bit about voltage. Most controllers nowadays use FETs, and FETs have a rating called Vbrdss (voltage breakdown, drain to source) that indicates how much voltage they can "switch against." If the voltage exceeds the Vbrdss of the FET, it will either be damaged or will "avalanche" (turn on all the way, even when it's not supposed to.) This can blow the fuse (if you're lucky) or the FET or even the circuit board (if you're unlucky.)

    3) Vbrdss indicates what voltage the FET can withstand, but that does not mean that a 60 volt FET can be used with a 60 volt supply. When phases switch off, a "spike" of voltage is generated due to inductive flyback. This is supposed to be conducted back to power/ground by the body diodes of the FETs, but they are not always fast enough to 'catch' the spike. Thus, an inverter designed to operate at 48 volts is going to use at _least_ 55 volt FETs (if not 60 or 75 volt FETs.)

    4) You can't just go up in voltage on the FETs. Typically higher voltage FETs have higher on resistances, which means a lower current rating. If the controller's current limit is not adjusted to a lower rating, this can overheat the FETs and cause failure.

    5) Another gotcha - a 48 volt lead-acid system will be charged at 60 volts, and will float around 55 volts. A 36 volt lithium-ion system will be charged at 42 volts and will float at 42 volts. Generally you have to design the controller to handle the maximum voltage the system can see unless you have an interlock to keep the controller off above a certain voltage.

    Anyway, if you have a "48 volt system" then the system is likely really designed to operate at 60 volts. If you want to add one more 12 volt battery to bring that up to 60 volts, the controller will really have to deal with 75 volts. (Or 69 volts if you use an interlock.) To see if your controller can handle this (from a purely FET perspective) open it up, get the part # off the FET and look up its Vbrdss.
     
  9. ibdennyak

    ibdennyak Guest

    over voltage electric

    5) Another gotcha - a 48 volt lead-acid system will be charged at 60 volts, and will float around 55 volts. A 36 volt lithium-ion system will be charged at 42 volts and will float at 42 volts. Generally you have to design the controller to handle the maximum voltage the system can see unless you have an interlock to keep the controller off above a certain voltage.

    Anyway, if you have a "48 volt system" then the system is likely really designed to operate at 60 volts. If you want to add one more 12 volt battery to bring that up to 60 volts, the controller will really have to deal with 75 volts. (Or 69 volts if you use an interlock.) To see if your controller can handle this (from a purely FET perspective) open it up, get the part # off the FET and look up its Vbrdss.

    Thanks for the information. I am using a 31 cc engine to drive a PM motor as a generator, so I can raise the voltage of the system by revving it a little higher. It does give me more speed, but I didn't want to ruin the batteries by doing it continuously. Think I better just be happy with moving.........until I get the other one running again. Thanks.

    Denny
     
  10. From your description of how a brushless motor works, I think that the controller may be failing to function. The single jerky movement that I get may be due to one electromagnet being turned on and never changed.

    I suppose I'll take the motor off and try to get it open to look at the controller. If the FETs are busted, I doubt I'll have the soldering skills to replace them though (unless they're the sort of thing that plugs in, which I doubt).
     
  11. billvon

    billvon Guest

    A great overview of how to fix a controller (a Crystalyte, but same basic rules apply)

    http://www.endless-sphere.com/forums/viewtopic.php?t=764
     
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