DC motor control and snubber circuits

[hotrodder]

This is all witchcraft to me but basically i have a 24V DC 16A gear reduction motor (with brake) i want to control via PWM with a double pole double throw switch for direction control. I recently won the 20A version of this for a power supply (assuming it copes ok starting under load, if not i'll try blowing it up with electrochemical weld cleaning experiments)

I can get my tiny mind around connecting everything up OK but do i need to worry about adding a snubber circuit for (potentially at least) long term survival of the power supply/PWM or is that sort of thing already taken care of when buying these as complete units or part of the reason why PWM controllers are either dirt cheapnese or 'kin spendy?

If i do need to worry about a snubber then how do i go about it (witchcraft remember!)? The internet talks about several methods... basic diode no good with reversable motor which leaves RC and varistor / zener diodes. Everything i've looked is talking about much smaller motors so i've no idea if the power involved narrows the choice (what's available/costs) etc. What about component 'sizes'... found various calcs but they all use values which are unkown to me. Is there a simplish way of guestimating things?

Thanks in advance and please try to avoid talking in component part number short hand

 

[MattF]

Your speed controller should have anything it may need built in to the circuit.

 

[Shox Dr]

000001111000001000001110011010110000111000000110010101010100000000111111000000111110111000000011100001001010101010100000000001111111000000001111000000111101010101010111100001101010100111101010101111111111111000000001101010111101010111010101001


If that doesn't work sorry I cant help.

 

[hotrodder]

Cool that makes life simpler, cheers

000001111000001000001110011010110000111000000110010101010100000000111111000000111110111000000011100001001010101010100000000001111111000000001111000000111101010101010111100001101010100111101010101111111111111000000001101010111101010111010101001


If that doesn't work sorry I cant help.

As Bender would say

011000100110100101110100011001010010000001101101011110010010000001110011011010000110100101101110011001010111100100100000011011010110010101110100011000010110110000100000011000010111001101110011

 

[Shox Dr]

I was going to google that. But couldn't be bothered as a nod to Bender

 

[chriskelland]

Shouldn't be any problems, If this is a variable speed controller you should be able to set the ramp up and down time. Is the motor starting under load? The one thing you will need to know is the stall current, if it's starting under load the current could rise by half as much again at start up. Set the ramp time to about a second that will give it time to start moving before hitting full power. You should not need anything else, by the way what are you using the motor for?

 

[hotrodder]

If/when i get it sorted it'll be used for various sheet metal tools, most of the time it'll live on the jenny swage at home- various bodies at work that complain more than a leccy motor but are (in most cases) more intelligent.

Variable speed control will be via pulse width modulation, motor is switched on and off at 100s of kHz and varying the dutycycle alters the speed. The motor has more than enough guts for the jobs at hand, the only info on the motor i have is the usual operating stuff, 24V DC / 16A, 2450rpm with output specs of 60Nm / 32rpm. Whether the 20A power supply has enough balls to start it under load i don't know yet but it was dirt cheap 2nd hand and i have other uses for it if it comes up short. I think it'll be fine and i can always gear it down 2:1 if needs be

 

[AndyStobbs]

Is that a BLDC motor then? Ace bit of technology those things. Max torque at any speed, even a neoludinite like me can see the progress.

 

[hotrodder]

No idea if it's brushless or not... if it's got brushes they're buried inside instead of easily replacable but there's only 2 wires poking out of the casing + another two for the brake which is a seperate module. Not had it apart to investigate further- finally got bored of tripping over it i thought it was about time i did something with it.

Looks identical to this one and came out of stairlift http://www.tornado-drives.com/produkte/kundenspezifische-antriebe/?lang=gb#c170