Checking out a no-name motor

I have a no-name motor I am checking out, let's see if you think these tests are good:

1. I have three phase wires and 5 hall wires. Hall wires were suspiciously cut off when I obtained this motor.

2. When I apply 5V to the red and black hall wires, I get no voltage signals out of the other three when I spin the wheel. I assume this means the halls are cooked. I cannot dissassemble the motor covers, so I'm going to assume that they can't be replaced. Covers are not installed with screws like most motors.

3. Wheel spins freely in one direction, makes noise in the other. I assume this means it must be a geared motor with a ratchet.

4. When I spin the wheel, and touch two phase wires, the wheel spins harder. When I touch all three phase wires, it spins harder yet. This works for all combination of phase wires. All phases measure about 0.3 ohms between wires (this at the bottom of what my meter can resolve) so it does not look like anything is shorted in there. I assume this means the motor is basically functional.

5. When I spin the wheel I can measure an AC voltage between all pairs of phase wires.

6. When I spin the wheel I can measure an AC frequency (my multimeter has a frequency setting) at all phase wires.

7. I have a controller, but the motor does not do anything but bump when the controller is hooked up and throttle sense wire is connected to 5V. I am very suspicious that this controller is bad but the motor is good. Haven't proved it.

8. Can I run this with a sensorless Grinfineon controller? According to the FAQ on ebikes.ca, Grinfineon controllers can run sensorless up to 28000 eRPM.

9. Turning the wheel at 5 seconds per revolution, I measured about 7 cycles per second at the phase terminals with a frequency-measuring voltmeter. (Fluke for the win!)

10. Doing the math, eRPM = #magnet poles X gear ratio X mechanical RPM of the wheel.

5 seconds per revolution = 60/5 = 12 RPM.
7 cycles per second = 7*60 = 420 cycles per minute
I have no way of separately measuring number of poles and gear ratio. But the product of those can be measured
If I assume 18 poles and gear ratio of 2, then 12 RPM X 18 poles X 2 gear ratio = 432 eRPM which is close to the frequency I am measuring. So for now I will assume that it is 18 poles and a gear ratio of 2. Or 36 for the product of the two, whatever the number of poles.

If I want to have a ground speed of 20 MPH 20X5280/60 = 1760 feet per minute
Circumference of a 20X175 tire is 60.15 inches, or 5.0125 feet
RPM of this tire at 20 MPH is 1760/5 = 351 RPM
eRPM is 36X351 = about 12600 eRPM.
It looks like the Grinfineon controller will do this sensorless since it is less than 28000 eRPm

Any of this make sense? What else would you do to test this no-name motor?

llile said:

2. When I apply 5V to the red and black hall wires, I get no voltage signals out of the other three when I spin the wheel.

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if you don't use a pullup resistor (1k-10kohm usually works) from the signal line to the 5v, you won't get a signal, because motor halls don't output anything, by design. they only ground the existing voltage whenever they're turned on by a magnet passing.

the controller does this internally, so if you test it with the halls hooked to the controller, and the controller is powered up, you should get valid signals.

Covers are not installed with screws like most motors.

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some covers are threaded, on small geared hubs. if so, you can look for the splines or grooves in the cover, usually near the axle, possibly under the freewheel if it has one. if you attach good pictures of the entire motor we may be able to help you find out how to open it, if it is necessary to do so.

there are a few motors that pull apart axially instead, usually after first unlacing them from the wheel. these generally have an obvious seam in the middle of the hub, between the flanges.

3. Wheel spins freely in one direction, makes noise in the other. I assume this means it must be a geared motor with a ratchet.

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probably. that's normal for one (though they don't usually ahve ratchets, they usually have a roller clutch).

7. I have a controller, but the motor does not do anything but bump when the controller is hooked up and throttle sense wire is connected to 5V. I am very suspicious that this controller is bad but the motor is good.

Click to expand...

if the controller is sensored only, then it must have the halls hooked up, and the phase and hall wires must be in the right order for that motor and controller combination. this can be determined experimentally in just a few steps. we'll go over that if necessary.

8. Can I run this with a sensorless Grinfineon controller?

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probably.

If I assume 18 poles and gear ratio of 2, then 12 RPM X 18 poles X 2 gear ratio = 432 eRPM which is close to the frequency I am measuring. So for now I will assume that it is 18 poles and a gear ratio of 2. Or 36 for the product of the two, whatever the number of poles.

Click to expand...

the gear ratio is usually more like 5, some are higher; havent' seen one that's lower but there could be.
number of poles varies, but it's often fairly low. if you can measure the phase wire pulses, then you're measuring the magnets spinning past. each pulse is a pole. unfortunatley you don't know the actual motor rpm without knwoing the gearing to determine the number of magnets (which, divided by two, gives the pole pairs)...but it doesn't matter; as you say it's the total number of pulses out per wheel rpm that's important.