# How do I match DC drives to DC motors.. and how do I test them?



## itsme_Bernie (Jan 2, 2021)

Hello Everybody
  If any of this is already described elsewhere, I would appreciate links to any message threads, or websites that describe what I'm confused about, if it has already been covered.
  A little while ago I purchased a number of DC motors and DC drives from a guy who had been "collecting" them to (but had barely began to) match them together.  Any that he could repair, he would if he could.
  One was already "matched", but now I want to begin to test, and then match as many remaining working motors to remaining working controllers.  Many of the motors and controllers I end up not matching together, that won't suit my machines, I may be selling off or finding homes for.
  I don't want to burn anything up for a stupid reason like connecting inappropriate motors/drives together.  After extensive Googling, (possibly using incorrect terms?) I am having a hard time making sure which numbers need to match, or which numbers need to be "less than", or if the motor specs should be much "less than", and when.
SO:
-I would like to learn how to match appropriate motor specs to drive specs
-I would like to know the importance of DC motor "armature voltage" vs "field voltage" (unless I REALLY don't need to know)
-I would like to know how far below the Driver-voltage can the motor be, or does the motor-voltage need to be higher than the driver-voltage?  Or does it need to be exact?
-Is just wiring up possibly-correct motors and drivers together and powering them on a reasonable way to check them? or should I put the Fluke Meters and look for certain readings on motor leads or driver connections first, somehow?
-What do I do when the DC-Driver has no specs, or limited specs?  It has been VERY hard to find vintage PDF's of brochures, manuals, catalogs to glean this information, even for Bodine, who is still in business (I called them!).  Maybe I should try calling them again?
-I heard that the TYPE of DC motor might effect driver choice, as regards matching a drive to either a Permanent-Magnet, Series, Shunt, or Compound motor.. Is this true?
  I can post pics of more motor spec-plates and driver spec-plates (if there they have one)
-All of the motors in question are permanent magnet DC motors, Porter Peerless, Dayton, and one really nice Leeson (**this is one of the first I want to match up, it's new**)
-I have a few different Reliance IMPAK "V-S" drives- one non-"V-S", a nice Bodine drive, and a Dayton drive.
For instance.. 
.
One of the IMPAK drive's plate says:
1.5 HP
AC  230v 9.5 A. RMS. 50/60 HZ.
       ARM 180v 7.5 A. AVE.
DC  FIELD 100V. 2A. MAX
.
A Leeson Motor plate says:
1.1kW (1.5 HP)    F.F. 1.05    D.C. AMPS 7.0
.75kW (1.1 HP)    F.F. 1.40    D.C. AMPS 4.9
RPM: 3000   D.C. Volts: 180 
(This is a nice motor, but is "metric" or something, and does not give NEMA, but IEC numbers)

Do these go together?  
I attached pics of these plates to this post.
... So the most powerful DC motor attached to this should be above or below 100V?
I am assuming the motor should be less than 2A at that voltage.

Thank you for reading!  This was the SHORT version of this post!

Bernie


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## hman (Jan 2, 2021)

DC motors generally come in two "flavors," depending on what kind of stator ("field") it has - permanent magnet or electromagnet.  If an electromagnet, it requires DC power.  Some of the latter type of motors allow the field wiring to be connected to the armature wiring, either in series or parallel.  Other motors with a wired field require a separate (constant voltage) DC supply.  Your power supply has two sets of output terminals.  The terminals labeled "Arm" or "Armature" connect to the motor's armature (thru the motor brushes).  The other set, labeled "field" would be wired to the stator of a motor that has a field electromagnet.  Or they can be left unconnected for a permanent magnet motor like yours. 

The specs on the power supply that are of interest for your motor are the (maximum) values for armature voltage and current.  These look like a good match to the motor.


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## itsme_Bernie (Jan 2, 2021)

Wow, thanks John!!  You taught me a lot already!
So as regards the motors I mentioned being all permanent magnet, I can "ignore" the Field specs.
... and if I find other motors that are NOT permanent magnet, I should keep an eye on Field specs that would be listed on the DC motor plate I guess?
NOW.. Should I be testing/taking readings through the motor, or the drive, before hooking them together?  What usually dies on these motors or drives that could end up not working?  Can then damage each other?
Thanks SO much

Bernie


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## RJSakowski (Jan 2, 2021)

Two parameters are of importance;  voltage and current. A driver can output a lower voltage than the d.c. motor is rated for at a loss in maximum speed and available power. I motor should not have a higher current draw than the driver can supply although some drivers have settings for the maximum delivered current and the motor will safely operate but at reduced maximum power.

From the specs that you have given, you should be OK as they are both rated for 180 volts and the current output from the driver exceeds the motor current.  You can ignore the field current spec since the motor is a permanent magnet motor.


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## hman (Jan 2, 2021)

Happy to help.

Regarding "field" specs - you got it.

Testing the motor - Motor windings generally fail open or short.  Hang an ohm meter across the motor terminals to check this.  Give the shaft one slow rotation by hand, so that you check each of the commutators and rotor windings.  Resistance will change a bit as the brushes alternately make contact with one or two commutators, but should never go short or zero.  You should also check the motor brushes (remove them one at a time, and replace in the same orientation they were originally).  Basically, you're looking for lengths below 1/8" (or 1/4"?), which would indicate the brushes are ready for replacement.  Once you've done this, you're ready to try the motor under power.

As for the power supply, as long as the maximum armature voltage isn't too far (~20% or so?) over the motor voltage, and the maximum current rating is equal to or greater than the motor's rated current, the easiest thing is to just go ahead and connect them and try them out.  If the voltage is correct, the motor will only draw the current it needs.  If the motor runs, both the motor and supply are OK.  If the motor doesn't run, check the armature voltage.  If it's zero (and you've checked the motor for shorts), the supply may well be bad.  Just be careful - 180 volt is dangerous!

Unless the motor has a short, it shouldn't damage the supply.  If it's open, it just won't run.  And as long as the supply's max voltage is close to the motor's, the supply shouldn't damage the motor.  

Disclaimer - I'm pretty sure this is all valid, but I'm not an electrician.  And yes, there's lots of fine details and rabbit holes that can complicate things.  But this should get you started.  PS - @Bi11Hudson is very knowledgable in all things electrical.  If he decides to join in, his post will be worthwhile reading in detail.  And ANY difference(s) between us should ALWAYS be decided in his favor!


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## markba633csi (Jan 3, 2021)

Permanent magnet motors act like generators- they can be easily checked. Turning by hand, you should see a small voltage at the leads
Most controllers are old technology SCR type as opposed to Mosfet and very rugged. They usually have a fuse or fuses to protect them too
-Mark


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## itsme_Bernie (Jan 5, 2021)

hman said:


> Happy to help.
> 
> Regarding "field" specs - you got it.
> 
> ...


Hman, markba633csi,
Thank you SO much.  What you are both telling me makes sense.. 
I worked with an electrician in college, wiring businesses and houses, but my learning curve understanding how circuits work etc is pretty steep t this point, hahah
Maybe I will nudge @Bi11Hudson, even if he doesn't have time to answer for a while, so anyone searching this in the future will get the best scoop they can (and for ME hah hah)

I think you have me off and running, and I cannot thank you enough!! 

I will ask, just to keep working on my learning curve (so whenever anyone has time, no rush):
What makes so many of these drives show up on auction sites so inexpensively?  I guess people like me don't know how to test them, so they are just unloading them?  It would seem a worthwhile risk to purchase a few and get one or two good ones, and maybe repair another

I will post my updates in the next day or so

Thank you!!

Bernie


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## hman (Jan 5, 2021)

Bernie, you're very welcome.
I really have no idea why the drives are showing up often or inexpensively.  It's not something that I've tried to buy or look for.  Might well be worth your while, once you've checked out the ones you already have.  Do you have a bunch of projects in mind, or are you planning to sell "matched" drives and motors?  I'd be willing to bet that a "tested and known good" matched set would get a lot better price than the components sold separately.
Best wishes for your enterprise, and keep on asking questions!


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## Bi11Hudson (Jan 5, 2021)

Better late than never????? Well, late but here means I'm still alive, anyway. I found the link to your question just a few minutes before a higher priority had to be dealt with. But, I'm here now and can expound on my (limited) knowledge of the subject. For the most part, I have working knowledge rather than schooling. So I do thing a little "left handed".

_For starters, let's differentiate motors and "drives". _DC motors come in many configurations. I have worked with a "servo" motor in the 5 HP range. And an "overhauling" motor that was 25HP or so. The "overhauling" is my term for a motor that is powered in only one direction. Lowering was accomplished by applying a small raising force that was less than the load. So it lowered slowly. When enough power was applied, the motor would hoist. Quite a machine, taken in its' entirety.

DC motors have a field and an armature. The armature leads are usually labeled "*A-1*" and "*A-2*". The fields is where it gets weird. There is a "shunt" or parallel field. This is the most speed stable form. The fields are, again usually, "*F-1*" and "*F-2*". Then there is the "series" field, where torque is the determining factor. the field will be marked "*S-1*" and "*S-2*". Higher still is a "compound" motor, which is then divided further as "short shunt" and "long shunt". There may well be multiple windings that are brought out with the same designation but higher numbers. *A*, *F*, and *S* are the keys.

Then there is the "Permanant Magnet" or *PM* field. This is the ultimate in speed regulation with a steady load. But there are many down sides, not the least being lower torque. The key factor here is "steady load". As the load increases, the speed will be reduced. (And vice versa to some extent) Another downside is that a PM motor cannot be run above base speed through a technique called "field weakening". But that is not usually done on small motors (<5HP) anyway. PM motors are quite common for small applications where speed and load are relatively constant.

The first rule of ALL* DC motors is that they must never be run without the field connected*. And a straight series motor never without a load. There is always a small residual magnetism present that will cause the motor to continually increase speed until it literally throws itself apart. The end result of which is not pretty.

With the basics covered, let's now look at drives. For simplicity, I will only delve into PM motor drives. For others, you need to find a good school on the subject just to know the terminology. Then, you can learn *why* they work. Only then can you learn *how* they work. It goes on from there.

In its' simplist form, a resistor in series with the motor will serve to lower the speed. From there are many forms of control, some electrical, some electronic. Most electrical controls consist of "dropping resistors" in some configuration. Most electronic controls involve SCRs or transistors. Although "duty cycle" controllers have become more and more popular in recent years. Duty cycle control uses pulses of full line voltage/current of varying width to vary power. They work very well, but are electrically noisy.

To test the controller, two light bulbs in series will serve up to 240 volts. As speed is increased, the lamps will glow brighter. And conversly, as it is lowered, they will glow dimmer. At the very low end, they can't be seen. But if they work well enough in the higher speeds, that means the controller is usually good. At least on the basics. 

That alone will serve to prove the controller is at least functional. There are countless derivitives of controller "brands", functions, special functions, voltages, ad infinitum, ad nausium. Since each model is individual, I cannot expound on what you have on hand. You will be on your own there. Test with the light bulbs for a basic "go/no go", find blown fuses, loose connections, and the like.

Try to keep voltage to voltage for motor to control. A 90 volt motor should not directly connect to a 180 volt controller. That should be obvious. A 180 volt motor to a 90 volt controller would be alright. It just won't run top speed. There are many "shenanigans" to reduce line voltage. Not the least of which is to run 2 motors in series. Just try to balance the load a little, if possible. There is *some* give with DC motors. A 12 volt PM motor will run on 18 volts. Albeit a little warm. But would otherwise survive. To run it on 24 volts would be questionable at best. and at 36 volts, keep a fire extinguisher handy. The same thought applies with the higher voltages you are pursuing. There are limitations and usually reveal themselves when the smoke gets out. And that *smoke is a lot harder to get back in than it was to let out*. 

Contact me if you have any further questions. Please use eMail, though. I don't usually answer even that right away. Most electrical questions require some thought. I'm an old man, and usually need to "talk down" to the less qualified. Often just to translate "old school" terminology into something useful. 

.


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## itsme_Bernie (Jan 9, 2021)

Bill.. I don't know what happened to my response a few days ago!  I am pack to pose another question and don't see it here!
I have been reading and rereading your post all week!
I am lucky to have a Hobby-Machinist school here to attend
Thank you so much.  I am getting a grip on all this and will have some results to share in a day or so

Bernie



Bi11Hudson said:


> Contact me if you have any further questions. Please use eMail, though. I don't usually answer even that right away. Most electrical questions require some thought. I'm an old man, and usually need to "talk down" to the less qualified. Often just to translate "old school" terminology into something useful.
> 
> .


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## Bi11Hudson (Jan 9, 2021)

Some afterthoughts:

It has been mentioned that a PerMag motor can be driven as a generator. In actuality, *any* DC motor is also a generator. Which is just a matter of whether a "load" or a "prime mover" is connected. Many(most) diesel-electric propulsion ships use the generator connected to a battery to "motorize" the prime mover (diesel) to start. There are exceptions, I served on one. But most do. Railroad locomotives use the same process. It is necessary to have controls for the field to some extent, but depends on the situation. Basically, the "generator" is also the "starter" motor.

Another thought that doesn't really fit your situation is to reverse a series DC motor with only two(2) leads. The series field is routed through a diode bridge rectifier mounted at the motor. The bridge carries armature current, so for large motors (over a very few HP) is not really an option. I had devised the solution for a bridge crane in 1978 or 79. Reliance Electric picked up the thought and used it on their DC drives later. But most of their drives were for shunt fields, so the connections were a little different. My implementation was to reduce the number of "trolley slides" (hence wires) on a bridge crane.

.


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## itsme_Bernie (Jan 10, 2021)

Bi11Hudson said:


> Some afterthoughts:
> 
> It has been mentioned that a PerMag motor can be driven as a generator. In actuality, *any* DC motor is also a generator. Which is just a matter of whether a "load" or a "prime mover" is connected. Many(most) diesel-electric propulsion ships use the generator connected to a battery to "motorize" the prime mover (diesel) to start. There are exceptions, I served on one. But most do. Railroad locomotives use the same process. It is necessary to have controls for the field to some extent, but depends on the situation. Basically, the "generator" is also the "starter" motor.
> 
> ...


Man, I am copying everything you guys are telling me into a "note" on my computer.. nothing like learning from people like in school (wow, what happened to me?)


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## itsme_Bernie (Jan 10, 2021)

Anyone recognize this threaded plug on the motor?  Or what type of connector it is to get me closer to finding it?  It would be pretty FANCY to find a plug to leave the controller/driver to the motor!


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## Bi11Hudson (Jan 11, 2021)

itsme_Bernie said:


> Anyone recognize this threaded plug on the motor? Or what type of connector it is to get me closer to finding it? It would be pretty FANCY to find a plug to leave the controller/driver to the motor!


In the first place, I am purely *speculating*. Without taking the motor in hand and making measurements, it would be impossible to say for sure. In its' simplist form, at first glance it is a "nominally" watertight line cord connector. My opinion is that it can be replaced with a line cord and wire restraint. Since there are only two wires coming out of the motor, I would speculate that the Red wire is A-1. The plastic block looks like a terminal point and nothing more. For sourcing one, I would look at a European or DIN source for _electrical_ parts, *not electronics*.

I personally use https://expert.alliedelec.com/ and https://www.mpja.com/. The former is oriented toward new components and the latter is a "salvage" house, meaning the products come and go relatively quickly. They both are "industrial" in nature and both easy to work with, even in small quantities. While the adverts appear electronic, there are a number of parts that are electrical in nature. There is a fuzzy area where the two crafts overlap and these are the two vendors I use for that area.

Think of "Radio Shack" from the mid '70s when they didn't carry "toys" and telephones and computers. Allied is the original before the retail outlets were bought by Tandy Leather. Either one may have the connector, and if it gets too wierd or costly, both have watertight cable clamps.

.


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## itsme_Bernie (Jan 13, 2021)

Gotcha.  I have been searching connectors that show the measurements and voltage and amperage specs and I'll post when I have success


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## itsme_Bernie (Jan 18, 2021)

I am a bit of a dork.  There are only two wires and a ground connected in that box.  I like the idea of the treaded, pinned connector, since it won't easily come apart.  SO I just found some 600v, 10amp connectors that I can replace in the box on the motor.   
I will show this when I get them in my hands.


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