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Thread: Marquip Servo

  1. #1
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    Default Marquip Servo

    I have a Marquip servo motor and I have not been able to find the power requirements as yet.

    It has a PN of 9601606 and a SN of 5011/6353170
    case is 3.25" in dia. X 8" long
    Has a 1/2" dia output shaft with a 1/4" encoder shaft
    mounting bolt circle is about 2.5"

    If anyone could supply me with operating voltage, current draw and max RPM I would be glad to hear from you.

    Thanks

    paul

  2. #2
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    Default

    Is this a brushed or BLDC/AC type?
    There are certain ways to find servo characteristics.
    Max.

  3. #3
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    Default motor type

    This is a brushed PM motor. It has one pair of brushes. The motor leads are approximately 16 gauge.

    I was thinking of checking with Helwig Carbon to see what they thought about the current capacity of the brushes...

    Can I derive any useful information if I were to measure the current draw at 24 volts and then raise the voltage to 36 and check current there? Does motor current go up linearly with voltage increase though out the operating range?

    The motor barely turns at 12 volts... leading me to believe that the actual motor voltage might be quite a bit higher... possibly 90 volts. The original motor had a tach on the small shaft, but it was damaged when I got it.

    I have mounted a CUI encoder on the small end. Might be jumping the gun considering I don't even know what the operating voltage is.

    Hope to use this for the leadscrew drive on a cnc lathe conversion

    Thanks

    paul

  4. #4
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    Default

    A lot of those motors run in the 80v area, some even higher. Put a tach on it and start turning up the voltage. These kind of motors are usually happy around 2000 rpm. I would suspect the motor is in the 200 to 300 watt range.

  5. #5
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    Default

    One way, assuming the maximum rpm for this motor is around 2000rpm which has been stated is typical for this type of motor, back feed it at 2000rpm and check the generated voltage, this will equal the maximum applied voltage.

    This is some notes I made when I was looking for similar information and found them in various sources:
    Personally I think that a simplified model of a DC motor can be derived
    assuming the armature inductance to be zero and ignoring the resonance
    effect. With these stipulations the equations are:
    1. V=Ia R + Ke omega (Ia=armature current, R=armature resistence,
    Ke=electr. constant, omega=speed)
    2. Tg=Kt Ia (Tg=costant, Kt=torque constant)
    3. Tg=J d(omega)/dt (J=inertia, d(omega)/dt=accel.)
    The DC motor transfer function is:
    Gm(s)=(1/Ke)/(1+s(Rj/KtKe)), which can be written Gm(s)=(1/Ke)/(1+sTm)
    where Tm=mechanical time constant.
    To measure the parameters you are asking for, I suggests the following:
    A. To Measure the armature resistance see note 2 below, then apply voltage to the motor without load and measure the current and speed. From equation 1. you can easily derive Ke.
    B. Apply nominal current to the motor (with the shaft locked) and by means
    of a variable voltage source. Measure the torque on the shaft. From this you can derive the torque constant Kt=Torque/Amp. See note: 3.
    C. You will find that Kt is approx. equal to Ke
    D. For the inertia you can obtain it by calculation from the size and
    material of the rotor.

    Note1: inductance can be ignored- the electrical time constant is
    very short compared to the mech time constant so that it can usually be
    ignored.
    You can measure the mech time constant by running the motor up to
    speed at no load, disconnecting the supply and letting it coast down- plot speed vs time and fit to exponential N=No(e^-t/Tm) time to drop to 36.8% of original speed is the time constant.

    Note2: If it is a permanent magnet motor, you can determine the internal emf by spinning it at rated speed and measuring the open circuit voltage. The voltage at any other speed will be directly proportional to speed. To measure the winding resistance, lock the rotor so it doesn't turn and measure the current with a small voltage applied (so as not to exceed rated current) Don't bother using a multimeter's ohm range- not worth the effort.
    For inductance, you should use a scope- apply a voltage, rotor locked and look at the current trace vs time.
    This will be of the form i=K[1-e^Rt/L] where i is the current at time t.
    In most cases the inductance can be ignored as its effects are generally swamped by the mechanical inertia in transient cases and is of little importance for steady state.

    Note 3: A pulley or lever attached to the shaft can be used with a string around the pulley and a spring scale used to measure the torque.
    Hope it helps a little.
    Max.

  6. #6
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    Default first test

    Thanks Max

    I am constantly surprised by the obvious... should have thought of the generator angle... oh well.

    I spun the motor at 1700 rpm and got 65 volts. That would be about 76 volts at 2000 rpm, which is near enough to the 90 volts that I suspected.

    More tests to follow...

    The next step for me might be hooking it up to a servo driver and power supply and see what happens for torque. Don't think that will be a problem, as my application will require about 200 rpm max, so I will be using a reduction belt drive.

    thanks for the help

    paul

  7. #7
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    Default

    What drive are you going to use?

  8. #8
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    Default drive

    I am considering the Gecko G320X but I am open to suggestions.

    I do want to use encoders. I thought the ability to use the encoder for the DRO function when the drive was not engaged would be a plus.

    That was the main reason I steered away from steppers. I could add encoders to a stepper, but I didn't find any drives that accepted the encoder input.

    paul

  9. #9
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    You do know the encoder does not go back to Mach, if this is what you are using?
    You would either need a controller that closes the loop or take the encoder back to Mach or other control of the same type.
    Max.

  10. #10
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    Default passthough

    In one of my bookmarks I have seen a board that passes the encoder data back to the pc... I should look for that again...

    I don't know about these:
    http://www.cnc4pc.com/Store/osc/prod...roducts_id=338
    But this appears to have the dro built into the drive...

    paul

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