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BLDC driver, power leads are sparking when shorted?

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player80

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Hi,

I have a 1.5kw BLDC driver here, when I unplug the driver and the leads of the cord touch some metal it sparks relatively strong.
There are quite a few capacitors inside the BLDC to guarantee smooth operation and power hikes I guess, but I have never seen that there's a spark on the power leads when they touch some metal after disconnecting them.

Is this really an acceptable behaviour? I'm concerned about safety. Next I will measure the voltage of the disconnected leads (I expect there should be some DC Voltage)

... just tested the DC voltage on it (certainly it cannot generate AC and backfire that one)... it's 220V and going down slowly... now I'm even more concerned about safety here.
 

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Easy peasy said:
No detailed diagram = no possibility of useful answer ...
Click to expand...
Sorry it's an off the shelf product, the issue is seen from a consumer point of view -- I can certainly open the BLDC driver and try to reverse engineer it however...

The question is are the power leads allowed to carry some voltage/power after disconnecting?
Is there any standard defined?
 

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Hi,

Until now we even don't know what's the input to the driver. Is it AC, DC, which voltage?

But a 1.5kW diver ... isn't equipped with a plug at the input. I guess (and thats all we can do) it is for non movable installation.
If this behaviour is normal for this device I guess there is an warning on the case or in the installation manual.

But I wonder why you can't tell the name of the manufacturer and the exact type.
At least a photo (~100kBytes) could be helpful.
Or did you build it on your own?

Portabke devices often have built in filters including a capacitor. Usually they use a bleeding resistor to discharge the capacitor within a couple of seconds.

Klaus
 

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everything's fine with the driver.

I expect I'm the problematic part here abusing the device with a 220V power transformer and a plug attached.
The device should not be detached and shorted like a consumer device (so I will change my setup here, to switch it off and disconnect the leads from the driver in an isolated box).
 

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Hi,

The internet page is a mixture of English and Cinese(?). Thus it's hard to find informations.

Try to install a about 270k Ohms bleeding resistor across the input. The resistor will continously dissipate power, thus rate it at least for 0.5W, better 1W.
Also it has to be specified for continously working with 250V AC.

Klaus
 

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There are requirements in safety standards, e.g. EN/IEC 61010. For accessible terminals, e.g. power chords, a discharge to safe levels within 10 sec is specified. If internal nodes have longer discharge time, warning labels on the instrument cover and handling instructions in manual are required.

The standards have also definitions of safe energy in terms of charge and stored energy.
 

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    player80

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FvM said:
There are requirements in safety standards, e.g. EN/IEC 61010. For accessible terminals, e.g. power chords, a discharge to safe levels within 10 sec is specified. If internal nodes have longer discharge time, warning labels on the instrument cover and handling instructions in manual are required.

The standards have also definitions of safe energy in terms of charge and stored energy.
Click to expand...

this is exactly what I was looking for thank you! The behaviour of the BLDC driver just made me curious about what is allowed and what not.

the power cord of that BLDC driver is probably not meant to be accessible -- thus I'm using it the wrong way (I have a CNC mill and CNC lathe, and I'm swapping the spindle power supplies).
Certainly someone can do that but extra care needs to be taken because the (industrial) product is not meant to be used that way.
That's what I have figured out so far.
 

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player80 said:
everything's fine with the driver.
Click to expand...
If the residual voltage is present only at the BLDC motor lines, a longer discharge time of e.g 30 - 60 sec, depending on the expectable disassembly time may be tolerated. A warning is nevertheless required according to my understanding. Mains power lines that may be wired to a plug should keep the 10 sec rules for safety standard compliance.
 

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    player80

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I measured:
80V after 10 Seconds (going down from ~220V)
20V after 20 Seconds
(on the disconnected main plug)

The device did not come with a power cord, I'm just curious could this be a regulation loophole?

(again it's an industrial device, not meant to be disconnected or possibly equipped with a power plug, and I was using it the wrong way)

>> EN/IEC 61010.

what a stupid standard ... costs 90$ so the end-user should just trust what he buys and not know about how standard electrical devices should behave. I know several IEC/EN standard documents cost money (I had to deal with them earlier already for quite some time) but in that case I highly disagree with it.
 
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Just unplug it, or switch off, at the mains zero crossing, this should leave a very low voltage residual on the AC pins ....
 

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