DC Motor. Which Type?

If it goes the other way with you excange the leads it is a PM motor. The exceptions are that it go "clunk" before it starts turning or it draws a huge current and goes very fast even on 12V.

Yes, but it is unlikely to be the use of those wires.

I suspect the 22 gauge wires are either connections to an over temperature switch intended to be used in an interlock circuit, or a tach generator output for speed feedback.

Runs with only two connections, has speed roughly inverse to load torque.

can have only two external connections, but speed varies much more than inversely proportional to torque. In other words has very high no load speed. If the nameplate has a speed rating, it is probably not universal (series) wound. Also, runs almost equally well on AC or DC. This also means that it turns only one way, regardless of polarity, so you have ruled this out.

Normally has 4 wires exiting the motor, so the shunt supply can be adjusted separately from the variable armature voltage (when used as variable speed motor). Also has a speed roughly inverse to torque load. If internally parallel connected, and intended for only full voltage operation, it will turn the same way, regardless of which way you connect the DC. So your test already rules this out.

You have a PM motor.

For large motors, yes. But there is usually a minimum size wire used for voltage rating, even if it is not needed for ampacity.

Permanent magnet DC motors are frequently 90 VDC so it probably is a PM motor. (and you only have two leads to make it go . . . it wouldn't turn at all if the field needed excitation or would turn slowly)

They see a lot of applications in exercise treadmills - but are also widely used in industry due to the very inexpensive controllers they require and single phase power.

PM motors reverse direction when the power is reversed.

Measure the resistance between the 22 AWG wires - likely to be a temperature sensing thermistor or over temp switch. Probably not a winding.

if you had a shunt motor, it wouldn't be turning. And thus, this leaves you with a universal type how ever, you did say that when reversing the wires the motor changed direction? so in this case, it would have to be a PM motor.

I deal with motors like that all the time. One application which all electronic geeks and college students can appreciate is the use of that type motor for the conveyor belt inside a pizza oven. The two smallest leads for the conveyor motors come from a magnetic pickup coil that picks up a pulse from a wheel shaped ceramic magnet on the end of the motor shaft. The pulsating output of the pickup coil is fed to the motor drive for the purpose of speed control ie cook time. The next time you visit your favorite mass production pizza place, ask someone if you may look at the drive unit for the oven belt. This same type motor is also used in automatic doors for grocery stores and hospitals.

So, in a few words, they might be tach leads, right? :-)

Now that I've nosed into the thread, I once saw a 90VDC 5 hp =:-O permanent-magnet motor. It was about the size of 1 1/2 loaves of bread on end.

Just by inspection, a PM motor won't have visible laminations on the outside - wound-field motors usually do.

I wonder what happened to the motor's nameplate?

Thanks, Rich

Cheers! Rich

Just a note, since the above could be read as series wound are only built with 2 connections. Series motor come in at least 2,3,4,5 or 6 connection variations. 2 or 4 are by far the most popular though.

I do agree this is mostly likely a PM motor though.

Robert

I think maybe the op may have been thinking of a universal motor?

We have Series would shunt motors that we deal with, and those do change direction when reversing. the series winding helps some times but does not always need to be used!

Could be, but hydralic pump motors often use the same type of wiring. They just aren't normally run on AC.

That sounds more like a compound motor. With both series and shunt wound fields. The series field acting to strengthen (or weaken) the field created by the shunt wiring. There are many true series wound motors with more than 2 terminals. And, of course, those do change directions unlike the 2 terminal motors.

Robert

Last week I was trying to find some information on Starter-Generators, aka Dynastart or Dynastarters.

These are often used on aircraft as 28V engine starters, and then battery chargers. They have a series field and a shunt field.

On the face of it they look like a compound motor/generator. But things are not as they seem.

It is a series-wound motor for starting, but a series-wound motor does not generate any voltage when spun in the direction of motoring. So, in order to generate an output voltage, the shunt winding then has to be energised to produce the correct polarity magnetic field .

The thing that is confusing (to me) is that any output current also goes through the series winding, in a direction that reduces the field generated by the shunt winding. The Ampere-Turns in the shunt winding must be very large to overcome the series field.

There is also the possible problem that the adverse compounding requires quite a lot from the voltage regulator circuit.

Does anyone have experience of Starter-Generators?