DC Power Supply Regulated, Unregulated or...!

[cadcamslawek]

Hi
My name is Slawek, CNC dude for 15 years; I like to build small CNC.

I bought:

1/8 HP 24 VDC MOTOR
New, M.E.T. model 3C-2413182C permanent magnet motor with brushes. Round body motor with no face or base mount.

SPECIFICATIONS
HP 1/8
Voltage 24 VDC
Amps 7.0
RPM 1,800
Reversible rotation
Totally enclosed Duty cont.
Shaft 3/8" dia. x 1-3/8" long w/flat
Overall size 3-1/4" O.D. x 7-1/8" long


Plan is to buy encoder(like to install them on ball screws), Gecko Drives 320, C11 Multifunction CNC Board + Mini power supply.

http://www.cnc4pc.com/Multifunction_CNC_Board.htm

http://www.cnc4pc.com/Mini_Power_Supply.htm

Now my problem is what power supply for these servos?
(Do not know a lot about electricity lol)

DC Unregulated Power Supply is batter to use or Regulated Power Supply or
Linear Power Supply or Switching Power Supply or any of this four will work (is linear same us regulated?)

If DC Unregulated Power Supply is OK, I tough this will work for me but, specifications:

MFG: International Power
P/N: IP500U24
Input: 110/220 VAC 47-63Hz
Output: 24VDC @ 20AMP (NO LOAD:29.2VDC)
Specifications/Features:
UNREGULATED Open frame linear supply. 4% Ripple at full load, No minimum load,Full rated to 50 Deg. "C" and UL/TUV/CE listed.
L: 9.00" W: 4.62" H: 5.62" WT: 18 [/I]


NO LOAD: 29.2VDC is this bad for my 24V DC Motor or not pleas help.

If you have any other toughs on my entire plan, setup and parts pleas write and help.
Sorry for my English

[NC Cams]

Motors are a bit more forgiving about a SLIGHT amount of over voltage. In this case, 29.2 volts is technically overvoltage BUT chances are, the power supply will lose a bit of voltage as load is applied to the motor and current demand increases.

The key think would be to limit the current to the motor via the motor driver circuit. Going overcurrent will cause demagnentization of a PMDC motor.

Overvoltage to the motor will raise the rated speed of the motor. If speed is regulate, this will be essentially irrelevant. If run at terminal voltage and with no load, you MIGHT run into overspeed problems.

With proper care and precautions, the motor and P/S should work OK - you'll still need to be careful.

[cadcamslawek]

Thank you NC Cams for reply.

So do you think I will be batter to use regulated power supply?
About current, the Gecko Drives deliver up to 20A so do I need to adjust these to 7A?

[pastera]

The voltage should not be a problem - the controller will be chopping the power to the motor to regulate speed, so the motor should never see a continous 29V. You also need to account for controller losses but if you are going to use geckos the drop will not be that much.

The voltage rating is more for top speed so you don't over speed the motor and gross overvoltage could cause the brushes to arc and burn. You shouldn't have that problem at 29V

With the gecko drive, you can adjust the current limit lower than the 20 amps, but should not need to. The motor current will be controlled by the servo drive to keep the motor in the correct position.
You will need to set up your controller properly so that you don't demand more torque of the motor than it can provide (acceleration values mostly)

Aaron

[Al_The_Man]

I never use regulated supplies for servo power, unless it is the right price
It is not really required, If you want regulated I would use Linear over switching, just because they are sturdier and easy to fix if they fail.
Also unregulated linear supplies are easier and cheaper to build for the equivalent power regulated linear or switching.
Al.

[cadcamslawek]

Thank you
All for tech support
Look’s to me like I can use ether one of this power supplies.
But now you did say:

“Unregulated linear supplies”

It means same us unregulated supplies?

[Al_The_Man]

Originally Posted by cadcamslawek “Unregulated linear supplies” It means same us unregulated supplies?

A typical unregulated supply consists of Transformer, Bridge Rectifier, Capacitor.
Al.

[cadcamslawek]

Thank you Al

[sswitaj]

For most stepper and servo motor use, you usually want to use unregulated supplies.

And the short answer is yes, your 24 volt supply will work just fine with the motors and drives your talking about.

Unregulated supplies are basic devices for providing bulk DC. Usually, as someone noted before, not much more than a transformer, bridge, and capacitor. Simple, and rugged, but the output voltage can, and does, vary greatly with load.

Electronic devices in general dislike this, so most of the supplies used for driving circuitry contain electronic regulation after the capacitor which modulates the output to keep it in a much narrower range.

But motors are usually not especially picky about drive voltage, especially motors that are fed with modern bipolar chopper drives. (the drives themselves often contain internal regulators that allow them to power their internal logic off the common supply).

Though it isn’t much of an issue with small motors one way or the other, as you move into the world of larger motors, regulated supplies have two distinct disadvantages.

First, in electronic terms, motors take a substantial amount of current, and all that current has to flow though the regulating circuitry, which does it’s job by either just burning off the extra voltage as heat (linear) or by throttling the current through reactive elements (switchers). Either way, those power transistors are expensive, especially at high power levels, and inefficient (losses of 30% are not common)

Secondly, and much more importantly, in any low-friction, system, motors do two things, they accelerate mass, but also they <I>de</I>celerate mass.

When you accelerate mass you do work, and consequently draw power from the power supply. But when you <i>de</i>celerate mass, you get energy <i>back</i> out of the load. The motor, (especially a servo motor) then acts like a generator. That extra energy piles up, and has to go somewhere.

In an unregulated supply, current simply flows back into the capacitor, piling up as excess voltage. If the cap is big, compared to the energy stored, this voltage rise is small and it very soon burns off.

But current usually can’t back up through a regulator (there are diodes in there), and quickly piles up voltage to damaging levels. This is especially a problem with switching regulators, most of are actually configured as current sources with voltage feedback, and they just loose their little electronic minds when the load becomes a source.

For this reason, most people don’t advise you use switching supplies in any but the smallest servo systems (like single-stack 23 frames)

Now granted, this is all pretty immaterial for normal 23 and 34 frame motors in a high-friction environment like a mill table. Frankly, any large, inexpensive, unregulated supply is going to do you just fine for a job like that.

But backdriving is an interesting technical point that you ought to know about if you ever work with big inertial loads (like spindles).

I have one application where a load moves 40 feet vertically, and

[sswitaj]

and when it comes down, the DC bus on the motor jumps from 325volts to 600 volts – and that’s <I>with</I> a big bank of resistors that kick in just to burn off the extra energy.

[cadcamslawek]

Thank you Thank you

Wow, this is what I needed to know

Thanks
Slawek