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Which power supply for PowerBrick LV?


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Hi all,

was wondering about the "best" way to supply a PowerBrick LV.

Required voltage 60V, the model has 4 * 5/15Amp amplifiers. (but 3 channels with max 3Arms each will be used)


Switching power supplies are cheap, lightweight and regulated but don't like regenerating current.


"Passive" supplies (Transformer+Rectifier and caps) can take current back but are not regulated. Transformers might be bulky. 3-phase have lower ripple. How much does the ripple affect the performance when you want the maximun precision?


Programmable laboratory labs are regulated, precise, low noise, some can even take some current back but are very expensive and normally are not made to be fitted inside a cabinet. Is the extra performance worth the extra expense?


Any guideline on actual choice? Or even some brand/model suggestion?

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Picking the right power supply needs to take into account the worst-case regen requirement for when the bus must absorb large kinetic energy while decelerating. Curiously, the manual for the PowerBrick LV makes no mention of any regen capability within the drive itself (??) Only that over and under voltage faults are triggered.


We have had good luck with "semi-regulated" power supplies from Puls for applications like this. They have some models which can absorb regen energy, and two units can be put in series for higher bus voltages. Check them out... https://www.pulspower.com/us/home/


Ed Merkle (630) 587-9780 is in tech support, and has been most helpful with application assistance.

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In our application, using Faraday Controls (i.e., Delta Tau UK pre-acquisition) rack-mount Power Brick hardware, we have both:


- the Faraday Controls Quad PSU:



- and a TDK-Lambda rack-mount supply with modular power supply inserts:



Pricing was a wash between the two units, at about $2 or $3k, so relatively minor on a per-axis basis given that each could run 32 axes, if motions are sequenced so not all are running simultaneously.



I missed seeing the 60VDC requirement, which nixes the Faraday Controls PSU.

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Haven't needed to operate anything at 60v myself, and in looking I see that the choices are indeed limited.

First off - as someone alluded to already - are you sure the Brick LV does not have a regen facility ???? Big omission in my mind, but given the range of potential bus voltages....

Here's what I would consider:

0) I share your concern regarding a switch mode supply. I wouldn't, unless I could add capacitance, a 'start-up' resistor circuit, and an isolating diode. Even then not my 1st choice.

1) Three phase unregulated supply with enough capacitance to absorb xx% energy with a +yy vdc rise (you have to define the xx% & yy bus voltage for your app).

I would say the ripple reduction of a 3 phase supply is worthwhile, but at low voltage & low power, capacitance is pretty cheap. Slew rate of the bus should be many orders of magnitude slower than your servo loops, even with single phase.

2) Since the power supply is unregulated, feeding it from a Constant Voltage Transformer (1% voltage reg) will help. These can be expensive enough that you may want to consider 1 phase supply instead of 3 and add some capacitance.

3) Here's where it gets difficult. Looking for a freestanding regen bus module didn't come up with as much as I would have found 10 years ago. It was more common then. Even more limited for a 60 v bus.


I did find this at Automation Direct. Regulates based on differential between supply & bus, across an isolating zener diode. Might be ok with a switcher (??) Provides some bus capacitance.


Cheap, rated 80v, 50W (100W with external resistor, 800W peak)



Automation Direct + Delta Tau Is that an oxymoron???


KB Electronics has a DC-DC drive (KBBC) that could be configured in a voltage feedback mode as a bus regulator. Likely would need a small inductance + power resistor so it looks like a motor rather than a resistive short. (dI/dt fault). Only rated at 48v, but with a voltage configuration setting of up to 1.25 rating allows 60v. But you'll need 65 or 70 to allow some capacitive energy storage before dumping.


If you have any volume on this KB can be pretty flexible.

Relatively cheap, you might even consider one of their AC-DC drives as a regulated supply to avoid the CVT in #2) above.

Kinda' a science fair project at this point.....

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Forgot to say I'm located in Europe so some of the suggestions might not be easy to source.


As for unregulated supplies this looks good and pretty cheap, but still need a braking chopper:



This one fron TDK-LAMBDA looks to be technically perfect GEN-60-12.5-PSINK but costs 2k€


I must admit I am a bit confused. Using a lab power supply is really worth the extra cost?

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Forgot to say I'm located in Europe so some of the suggestions might not be easy to source.


As for unregulated supplies this looks good and pretty cheap, but still need a braking chopper:



This one fron TDK-LAMBDA looks to be technically perfect GEN-60-12.5-PSINK but costs 2k€


I must admit I am a bit confused. Using a lab power supply is really worth the extra cost?


Something I have done before for battery charge and other DC power supply applications (should have mentioned this before) is to use a good old fashioned SCR, brush motor, 4Quadrant, DC drive.

- Cheap

- Single phase at standard line voltages with fully adjustable output.

- Three phase for more $$, less ripple

- Line regen. No resistor / no heat / no 'chopper' / 100% regen capacity

- Tachometer input can be used as voltage sense on PMAC side of bus filter, allowing fairly tight regulation (0.1-0.25%)

- Can use accel/decel settings for controlled power-up & bleed-down of bus.

- DIN rail mounting

- Example would be a Bardac K680XRi for ~US$800. Fully digital, ~7A @ 0-100vdc. Should be avail in EU, but there are many manufacturers. This is just one example.



- BUT! You still have to add bus filtering. The notching that the SCR's deliver (and to protect against dI/dt faults) will require a series inductor (+R?) followed by R||C. I would be tempted to add a zener in series with the R.

- The filtering is pretty simple and could be done on a terminal strip with standard components.

- The drive provides a regulated 10vdc output that can be split with a simple voltage divider as a control reference (stability more important than precision)


I'd estimate the whole thing at US$ 900-1000


As for the lab supply, I don't think a dead stable bus is that critical. You would be adding a chopper for regen. More important is that variation/ripple be << slower than your current loops in the PMAC.

For very high precision, it may matter more than I realize.


For the price, the unregulated supply you found with a chopper is worth a try. You can always add a little capacitance if needed. You'd be

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The Brick LV is rated to a "maximum voltage" of 80VDC. The listed nominal supply voltage is limited to 60VDC for thermal reasons -- operating continuously at 80VDC and rated current levels in a 45C ambient environment could overheat the drive. But occasionally increasing the bus voltage to 80V due to rapid deceleration is perfectly acceptable.


I think it is worth a close examination as to how much voltage increase you could really expect in your application, with the key factors being how you decelerate motors and how much DC bus capacitance your power supply has. Few real applications will ever create a 33% increase over nominal.


If your supply can also withstand 80V and has adequate capacitance, you may not need any shunt circuitry at all.

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  • 2 weeks later...

So basically a lab-grade power supply with current sink is not going to make things better precision-wise than a decent unregulated power supply?


The application is not going to regenerate much, btw.


So far I can envision 3 topologies:

1 Classic unregulated PS (trafo, rectifier and caps)

+Cheap +Can absorb power -Not regulated -Ripple

2 Switching PS + Protection diodes + (extra capacitance)

+Cheap -Can't absorb power, extra energy make voltage raise on caps +Regulated (but only when providing power)

3 Lab PS

-Expensive +Regulated, low noise +Can absorbe power ?Is it worth the extra price


Not really sure about what to choose...

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I don't see any reason to pay for an expensive regulated supply. Most supplies for servo drives are pretty simple rectifiers, and the DC bus voltage can vary quite a bit. While changes in the bus voltage are effectively a gain change, the use of current feedback to modulate the voltage supplied to the motor makes the performance effect of this change insignificant.


As you note, adding capacitance to the DC bus will reduce variation, both within AC line cycles, and over longer time spans.


Shunt circuits are used to protect against overvoltage damage, not to keep a tightly regulated supply voltage.

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We (Faraday Motion Controls) use an expensive regulated supply in our Quad PSU because it allows us to fit two 24V supplies (logic and IO) and a 1.6KVA 48V motor supply into a 1U high rack to power four Bricks. The Quad PSU also incorporates a regen circuit and has thermal circuit breakers to allow each Brick to be individually switched. Because it can power four Bricks, the cost per axis is reasonable.


We have previously used a simple rectified and smoothed DC supply but that occupied a 3U rack, was very heavy and generated a fair bit of heat from the transformer.


Both types of supply work well for most applications but the space saving is a valuable benefit for our scientific customers as they have so many axes control in a small space.

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