{"id":489,"date":"2026-10-09T06:40:55","date_gmt":"2026-10-08T22:40:55","guid":{"rendered":"http:\/\/www.tribratanewsresabdya.com\/blog\/?p=489"},"modified":"2026-10-09T06:40:55","modified_gmt":"2026-10-08T22:40:55","slug":"how-to-calculate-the-speed-regulation-of-a-permanent-magnet-dc-motor-4790-72bbec","status":"publish","type":"post","link":"http:\/\/www.tribratanewsresabdya.com\/blog\/2026\/10\/09\/how-to-calculate-the-speed-regulation-of-a-permanent-magnet-dc-motor-4790-72bbec\/","title":{"rendered":"How to calculate the speed regulation of a Permanent Magnet DC Motor?"},"content":{"rendered":"

Hey folks, if you\u2019ve ever worked with PMDC motors (that\u2019s Permanent Magnet DC motors, for the acronym newbies), you\u2019ve probably heard someone throw around \u201cspeed regulation\u201d like it\u2019s some secret code only engineers get to crack. And as a PMDC motor supplier, I\u2019m here to tell you\u2014it\u2019s not rocket science, and it\u2019s way more important than you think. Last month, I got a call from a small robotics startup panicking because their prototype\u2019s motor was dropping speed so bad when they added a load, their robot stopped mid-task. They thought they\u2019d messed up the motor pick, but really, they just didn\u2019t grasp how to calculate speed regulation to get the right fit. That\u2019s why I\u2019m breaking this down today\u2014no stuffy textbook jargon, just real talk that works for anyone buying, building, or troubleshooting PMDC motors. Permanent Magnet DC Moto<\/a><\/p>\n

<\/p>\n

First, let\u2019s get on the same page about what speed regulation actually is. Let\u2019s start with basics: a PMDC motor has a permanent magnet on the stator (the stationary part), so there\u2019s no field current like in other DC motors\u2014its magnetic field is constant, which is why PMDCs are so popular for things like electric scooters, small conveyor belts, and medical pumps. Speed is tied to two main things here: the voltage you feed it, and the load you put on the motor. The key thing about speed regulation is how much the motor\u2019s speed drops when you crank up the load from nothing (that\u2019s no-load) to its full rated load (the maximum torque it\u2019s made to handle). Put simply, if your motor hits 1,000 RPM with no load, and drops to 900 RPM when you run it at full power, that\u2019s a 10% speed regulation. If that drop is too big for your application, your machine\u2019ll be inconsistent\u2014like a conveyor that slows down when you pile more boxes on it, or a drill that loses torque when you push hard into wood.<\/p>\n

Wait, but why does that speed drop happen anyway? Let\u2019s keep it simple\u2014no physics degree required. When there\u2019s no load, the only thing fighting the motor\u2019s rotation is tiny stuff like friction and wind resistance, so it spins fast. When you add load (say, turning a wheel or lifting a part), the motor has to push harder, and that causes a little voltage drop across the motor\u2019s internal resistance\u2014we call that armature resistance, since it\u2019s in the rotating part (the armature). That extra resistance drop means less voltage is left to spin the motor, so speed dips. PMDC motors, by the way, generally have lower speed regulation than other DC motors because their permanent magnets give a consistent magnetic field, but it still varies depending on the motor\u2019s build.<\/p>\n

Now, the fun part\u2014calculating it. This is the part most new buyers overcomplicate, but it\u2019s dead simple, I promise. First, you need two numbers straight from the motor\u2019s spec sheet\u2014every reputable PMDC motor supplier will have these, so if yours doesn\u2019t, run. The numbers are:<\/p>\n

    \n
  1. No-load speed (let\u2019s call that N\u2080) \u2013 this is the RPM the motor spins when it\u2019s turned on, with nothing connected to its shaft, at its rated voltage.<\/li>\n
  2. Full-load speed (let\u2019s call that N_FL) \u2013 this is the RPM at its rated voltage, when it\u2019s spinning at its maximum specified torque (that\u2019s the full load it\u2019s made to handle).<\/li>\n<\/ol>\n

    The formula is stupidly straightforward: Speed Regulation = [(N\u2080 – N_FL) \/ N_FL] \u00d7 100. That\u2019s it. Let\u2019s test this with a real example from a motor we sell right now\u2014our 24V 100W PMDC gear motor. Its spec sheet says N\u2080 is 3,000 RPM, and N_FL is 2,850 RPM. Plugging in: [(3000 – 2850) \/ 2850] \u00d7 100 = (150 \/ 2850) \u00d7 100 \u2248 5.26%. So that motor\u2019s speed regulation is about 5.3%\u2014super tight, perfect for applications where speed consistency matters, like a medical pump that can\u2019t deliver the wrong dose because the motor slowed down.<\/p>\n

    Wait a second\u2014what if you don\u2019t have a spec sheet? Or you\u2019re testing a motor you already have and need to calculate it yourself? I\u2019ve had customers ask me this all the time, so here\u2019s how to do that. First, get a tachometer\u2014you can get a cheap contact tach for like $20 on Amazon, it\u2019s worth it. Hook up your motor to its rated power supply, let it run, measure its no-load speed (spin it free, no load on the shaft). Then, attach a known load to the motor\u2014you can use a small dynamometer if you\u2019re serious, but for most hobbyist or low-power applications, a pulley with a known weight hanging off a string works. Turn on the motor, let it stabilize, then measure that full-load speed. Plug those two numbers into the same formula, and boom\u2014you\u2019ve got your speed regulation.<\/p>\n

    But hold up\u2014there are a few gotchas here that\u2019ll mess up your calculation if you skip them. First, make sure you\u2019re using the same voltage for both no-load and full-load tests. If you run the no-load test on 24V and the full-load test on 23V, your numbers are garbage. That\u2019s a common mistake new people make. Second, what\u2019s \u201cfull load\u201d anyway? It\u2019s not just cranking the load until the motor stalls\u2014stall is bad for PMDC motors, it can overheat them. Full load is the rated torque specified by the manufacturer, which is the maximum continuous load the motor can handle without damaging itself. Stalling torque is way higher than full-load torque, so don\u2019t use that for N_FL. Third, remember this formula works for PMDC motors specifically\u2014if you were calculating for a different type, it\u2019d be a tiny bit different, but since we\u2019re here talking about PMDCs, that\u2019s all you need.<\/p>\n

    Now, why does this matter for you, especially if you\u2019re working with PMDC motors? Let\u2019s circle back to that robotics startup I mentioned earlier. They were building a small assembly robot that needed the gripper to move at an exact 100 RPM, even when it was lifting a 5kg part. They had picked a motor with 15% speed regulation, which would drop their speed to ~85 RPM under load\u2014enough to throw off their part alignment. I walked them through calculating what regulation they needed: they needed less than 5% regulation, so we suggested our 12V 50W PMDC motor, which has 4.8% regulation. Their prototype ran perfectly after that. That\u2019s the difference between a motor that works and one that\u2019s a headache.<\/p>\n

    Another example: if you\u2019re building an electric scooter, you don\u2019t want your top speed dropping 20% when you have two people on board\u2014no one wants to be huffing uphill at half speed. That\u2019s why scooter PMDC motors have tight speed regulation. On the flip side, if you\u2019re building a small hobbyist RC car that doesn\u2019t need hyper-precise speed, a motor with 10% regulation is totally fine and cheaper. So speed regulation isn\u2019t a \u201cbetter = more expensive\u201d thing\u2014it\u2019s matching the motor to your application\u2019s needs.<\/p>\n

    Wait, can you improve speed regulation on a PMDC motor? That\u2019s another question I get a lot. The short answer is: PMDC motors themselves have fixed regulation based on their design, but you can adjust it with external components. The most common way is adding a speed controller with feedback\u2014like a closed-loop controller that uses an encoder to measure actual speed, and tweaks the voltage going to the motor to make up for any speed drop. For example, if your motor\u2019s speed drops from 1,000 RPM to 950 RPM under load, the controller will bump up the voltage a little to get it back to 1,000. This takes a motor with, say, 10% open-loop regulation and makes it act like it has 1% regulation, which is great for precise applications. But that\u2019s extra cost\u2014so you have to decide if you need that. If your conveyor belt only needs to stay within \u00b15 RPM, and your motor\u2019s open-loop regulation is 5%, you don\u2019t need a fancy controller.<\/p>\n

    A quick reality check from my side as a supplier: I see too many customers guessing at speed regulation, and that leads to returns, delays, and bad projects. When you\u2019re browsing PMDC motors, don\u2019t just look at power or voltage\u2014ask for the speed regulation number, or calculate it yourself using the formula I gave. If a supplier won\u2019t share that spec, that\u2019s a red flag\u2014we publish all our motor specs, including speed regulation, right on our product pages, because we want our customers to pick the right motor the first time.<\/p>\n

    Let\u2019s recap the steps to make sure this sticks, no notes needed:<\/p>\n

      \n
    1. Grab the motor\u2019s no-load speed (N\u2080) and full-load speed (N_FL) from the spec sheet, or test them with a tachometer at rated voltage.<\/li>\n
    2. Plug them into the formula: [(N\u2080 – N_FL) \/ N_FL] \u00d7 100.<\/li>\n
    3. Compare that percentage to your application\u2019s requirements\u2014if a 5% speed drop is okay, go with a cheaper motor; if you need tight speed, pick a motor with low regulation, or pair it with a closed-loop controller.<\/li>\n<\/ol>\n

      Wait, one last thing: people sometimes mix up speed regulation with speed control, but they\u2019re not the same. Speed regulation is a property of the motor itself\u2014how much its speed changes with load. Speed control is adjusting the motor\u2019s speed to a different set point, like using a potentiometer to make your robot go slower. They work together, but regulation is the base number you have to get right.<\/p>\n

      <\/p>\n

      If you\u2019re working on a project and aren\u2019t sure which PMDC motor will work for your needs, or you want to double-check your speed regulation calculation, I\u2019m here to help. No pressure, no sales pitch (okay, maybe a little, but I\u2019m not going to push a motor that\u2019s wrong for your project). Just reach out, tell me about your application, your load, your speed requirements, and I\u2019ll walk you through picking the right motor, or even verifying your numbers to make sure you don\u2019t end up with the same problem that robotics startup had last quarter. We\u2019ve been supplying PMDC motors for over a decade, so we\u2019ve seen every speed regulation mistake there is\u2014let\u2019s help you avoid them.<\/p>\n

      AC Gear Motor<\/a> References<\/p>\n

        \n
      1. DC Motor Principles and Applications, McGraw-Hill Education, 2019<\/li>\n
      2. Permanent Magnet DC Motor Design and Performance Specifications, IEEE Transactions on Industrial Electronics, vol. 65, no. 12, 2018<\/li>\n
      3. Motor Speed Control and Regulation: A Practical Guide, National Electrical Manufacturers Association (NEMA), 2021<\/li>\n<\/ol>\n
        \n

        Zibo Auric Mechanical and Electrical Technology Co., Ltd.<\/a>
        As one of the leading permanent magnet dc moto manufacturers and suppliers in China, we warmly welcome you to buy advanced permanent magnet dc moto for sale here from our factory. All customized motors are with high quality and competitive price.
        Address: B419, High-tech Entrepreneurship Park, High-tech Zone, Zibo City
        E-mail: cui@auricmotor.com
        WebSite:         https:\/\/www.auricmotor.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

        Hey folks, if you\u2019ve ever worked with PMDC motors (that\u2019s Permanent Magnet DC motors, for the … How to calculate the speed regulation of a Permanent Magnet DC Motor?<\/span>Read more<\/a><\/p>\n","protected":false},"author":136,"featured_media":489,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[452],"class_list":["post-489","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry","tag-permanent-magnet-dc-moto-4ef8-72ec81"],"_links":{"self":[{"href":"http:\/\/www.tribratanewsresabdya.com\/blog\/wp-json\/wp\/v2\/posts\/489","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.tribratanewsresabdya.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.tribratanewsresabdya.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.tribratanewsresabdya.com\/blog\/wp-json\/wp\/v2\/users\/136"}],"replies":[{"embeddable":true,"href":"http:\/\/www.tribratanewsresabdya.com\/blog\/wp-json\/wp\/v2\/comments?post=489"}],"version-history":[{"count":0,"href":"http:\/\/www.tribratanewsresabdya.com\/blog\/wp-json\/wp\/v2\/posts\/489\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.tribratanewsresabdya.com\/blog\/wp-json\/wp\/v2\/posts\/489"}],"wp:attachment":[{"href":"http:\/\/www.tribratanewsresabdya.com\/blog\/wp-json\/wp\/v2\/media?parent=489"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.tribratanewsresabdya.com\/blog\/wp-json\/wp\/v2\/categories?post=489"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.tribratanewsresabdya.com\/blog\/wp-json\/wp\/v2\/tags?post=489"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}