Electronic – Driving Partly Specified DC Motor With AC/DC Power Supply

dc motordc-transformerledpower supply

I'm currently doing a hobby project regarding a wood cutting saw. To do so, I have bought a DC motor from a local seller. The seller provides this information only:

  • Voltage: 12-36V
  • Max Rpm: 15000
  • No load current with 12V: 1A
  • No load current with 24V: 1.5A

As a matter of fact, no rated/nominal voltage, current, and power values are available. However, once I researched on the web I found these:

  • Brand: Mabuchi
  • Model: RS-775SF
  • Power: 230W

Then, I bought a 12V/30A power supply (AC-DC transformer mostly used with LED strings) assuming that it could drive my motor up to 30A once I forced it (apply high load by holding the shaft with gloves ). Unfortunatelly it did not, it gives max 4.5A only.

I'm new on electronics and confused very much. I have a lot to ask but the main things are:

  1. First of all, is there any environment on the web to find the offical specifications of DC motors?
  2. What is wrong with my 12V 30A power supply? Isn't it supposed to give much more than 4.5A if loaded?
  3. Which power supply (or any configuration) should I use to drive my DC motor optimally if my design criteria is such: around 10000 rpm with 150W cutting power (1.45 kg*cm torque)?
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Best Answer

Based on the comments (later they have been moved to chat) and my subsequent work, I want to share my last position, self answer in a way. Because I finally succeeded to get what I want. And I know there will be newbies who face them exactly.

  1. No, there is not such a safe platform including all available DC motor specifications. Try not to buy/use electronic devices without datasheet, which are supplied by manufacturer. If it is inevitable:

    • Examine the motor if there is a label on it. Serial number might be written there. Just google by it hoping to find an another trustworthy seller who gives specifications about the same motor.
    • Again if serial no is available, maybe you can find some others (papers, Youtube channels, blogs etc) who have made 'parameter identification' and share the results.
    • Do system identification yourself. Really really big journey, I have not done it. Research. Keywords: Parameter Identification, System Identification, Parameter Estimation..

  2. There is nothing wrong with my earlier power supply. However; in addition to output voltage/ampere/power, protection standards (!?) of a power supply should also be considered. For example in my case, there was short-cut protection for my first p.s., so if huge torque coming from wood cutting (or if it is prevented from rotating by holding a glove to stops dc motor shaft) p.s. assume that there is an abnormality and shut down in case of fire or any other disaster. It is for LEDs so short-cut and its effects should be avoided.

  3. I was not able to find a specific type/name/branch/model etc. of power supplies for this purpose. As suggested in comments, again a datasheet is crucial. I should have known specially the stall current of p.s. in addition to its max current. Back to my solution; I reordered another one, but this time I asked to seller whether it could be used for stalling dc motors, he said no problem. Same voltage-ampere-power same price same size. But yet it works properly as the seller had claimed. It shuts down only if I do not use proper cables, since most cables cannot support 30A.

Summary:

  • Never underestimate protection standards (please correct me if any technical name for it) when using AC-DC power supplies.
  • Never think mechanically, same size-price-appearance (even power) could create huge difference. Datasheet datasheet datasheet :)
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