How to Select DC Motors Image Credit: Dart Controls, Inc.; Galil Motion Control; Stock Drive Products/Sterling Instrument   DC motors are electric motors that are powered by direct current (DC), such as from a battery or DC power supply. Their commutation can be brushed or brushless. The speed of a brushed DC motor can be controlled by changing the voltage alone. By contrast, an AC motor is powered by alternating current (AC) which is defined by both a voltage and a frequency.
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Q & A on DC Motors

We asked our users for their input on DC Motors. Here are the results of 351 users familiar with DC Motors.

Who Took Our Poll? | Design Trends | Applications and Use | Features | Buying Advice

Who Took Our Poll?Top

Design TrendsTop

Q:
What new technologies are influencing DC motor design?
51 answers
Answers:
DC electric motors are apparently more powerful and thus able to substitute for hydraulic / mechanical systems.
~DAVID P, Engineer, WESTLAND, MI
Micro-magnetics, better insulation materials, miniature hall-sensors, ESD protection for hall sensors.
~Engineer, Seattle, WA
The new uses in cars and vehicles in general, because the motor must have less weight and more power.
~Technical Support/Services, Madrid, Spain
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Q:
From your perspective, which companies are creating the most innovative DC motors?
39 answers
Answers:
I can't remember the name of the company as we used to purchase ours through a distributor out of Australia.
~Fredrick G, Engineer, Suva, Fiji Islands
Toshiba Mitsubishi General Electric Most of the larger manufacturers are adding to better performance
~Engineering, Consulting, Blue mountains, Australia
According to me, Johnson Motors is what I think creates the most innovative Motors.
~Akshay Gosavi, Student, Nashik, India
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Applications and UseTop

Q:
What are some of the applications you have used DC motors for?
95 answers
Answers:
AS CUTTER MOTOR
~MAHESH KUMAR G, Faculty/Staff, BANGALORE, INDIA
Mill drives, mine winders, traction, cranes, shovels, drag lines, paper mills, roller table drives, steel processing lines, copper rolling mills, toys and basically anywhere where you can use motors or generators.
~Mathys B, I am a retired electrical engineer, now doing consulting., Benoni, South Africa
Mostly as driving motors of belts in capacitor coil welding machines, main motors of capacitor winding machines and other machines related to capacitor production.
~Manufacturing, Hubli, India
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Q:
Please share with us any “non-standard” applications that DC motors have been used for.
34 answers
Answers:
I am only concerned with prototypes of new types of powered surgical instruments, so all the applications are non standard.
~Martin P, Design Engineer, Farnham, UK
For military applications, each vehicle appears to be "special" and requires a custom designed dc motor.
~DAVID P, Engineer, WESTLAND, MI
Medical devices such as infusion pumps (micromotors). Sample pumps (low noise good linear behavior etc.)
~Martin L, Technical Support, Hoorn, The netherlands
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Q:
Do you know of any disastrous mistakes that occurred due to the incorrect usage of DC motors?
25 answers
Answers:
One major problem is the quality of the DC motor control. If and when that goes bad, the user has to be careful when working/testing the motor. I nearly got my face smashed when the 200V DC motor suddenly went to high speed and flung the connected empty barrel at me! This was due to the faulty speed control. So better have the full load connected when trying out the operation.
~Manufacturing, Hubli, India
Oversizing the motor is bad for the carbon brush life and performance, which in turn will reduce your commutator life. Also, change the brushes more frequently as they are most likely the least expensive component on your equipment that has the greatest impact on your production output. Remember, a carbon brush prefers to be overloaded than underloaded.
~Ed S, Regional Sales and Service Manager, Lakeland, FL
Yes, built in motors with too bad carbon brushes. Too soft and bad expellation of carbon dust in such a way that the collector of the motor is running full with dust and therefore the torque goes down and current goes up.
~Martin L, Technical Support, Hoorn, The netherlands
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FeaturesTop

Q:
What would your design or feature "wish list" be for this product?
48 answers
Answers:
With only basic DC Motor training back in 1970 and as a hands on industrial technician I am always watching for new technology as it grows. The brushless DC motors and controllers are a real achievement and with the demand for portable quite drive applications, enthusiasts like my self can now build to suit. With the internet as a search engine and the sharing new technology brought to me and the world through GLOBALSPEC, I stay prepared to build for myself. I now watch for regenerative energy in DC breaking technology. Some day builders will have package arrangements for various control scenarios from large to small applications available on the shelf for do-it-your-selfers like myself. That may be pretty large for a wish list, but wouldn't it be nice to purchase brushless DC motors by power and speed, single or dual motor directional control with expandable accessories for different input control applications from a single stocking manufacturer?
~Engineering, Faculty/Staff/Student, Redding, CA
Usage (private / hobby) of good DC motors for transportation usage. Good weight to power ratio and high initial torque.
~Martin L, Technical Support, Hoorn, The netherlands
ESD protection of hall sensors in miniature brushless motors is a big wish that seems unsatisfied at the moment.
~Engineer, Seattle, WA
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Q:
Is there any advice you want to share with users to help them avoid common errors in selection or usage of DC motors?
27 answers
Answers:
Kt and Ke are strong functions of temperature, motors operating at temperature a may not deliver the same starting and running torque at elevated temperatures. This may cause your highly optimised motor to lock, jam or misbehave.
~SUBRAHMANYAM SISTA, CHIEF TECHNICAL MENTOR, HYDERABAD, INDIA
I would not oversize the motor. In other words, if you need say 90 HP to meet your requirement, do not buy any larger than 100 HP. 95% chance you will probably never even reach 75 HP requirements.
~Ed S, Regional Sales and Service Manager, Lakeland, FL
Use 1.5 times higher capacity motors for trouble free service, keep filters changing for cooling blowers regularly, check brushes and clean commutators regularly.
~Sanjay Nagarkar, Facilities Manager, 1Lagos, Nigeria
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Buying AdviceTop

Q:
Do you have any advice for people relative to buying or using DC motors?
32 answers
Answers:
Yes. Generally the motors of standard companies are of good quality and last for years. Even after many years, when problems do come, they are generally to do with bearings and not with motor winding itself. So see if you can repair them yourself by replacing bearings. The 'advice' given by the original manufacturer is always to buy new ones and that will prove to be very expensive. Your old motor still will have lot of life left.
~Manufacturing, Hubli, India
I work with hydraulics and use DC motors to produce the needed flow for small power pack units that are powered with 12 or 24 volt. Before selecting the DC motor you need to look at your working pressure and flow requirements. I had to go back to my salesman and recommend that they use a different crane that has a lower working pressure to get a decent continuous operation time vs cooling time.
~John M, Design Engineer, Perrysburg, OH
Please check complete specs for the unit which is compatible for your application. Especially Current,Voltage, Watts, and RPM ratings.
~Cruz Jr. O, Technical Support, Quezon City, Philippines
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