Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: fast89 on March 08, 2018, 06:16:16 PM
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Hello everybody,
I've got an Allen Bradley dsd-020 drive and motor as a spindle motor. Motor turns 5k and spindle turns 7500. It has quite a bit of regeneration when decelerating. I added an ALLEN BRADLEY 2090-UCSR-A300 shunt module. Well, i tried to anyway. I bought a used one on eBay and it wouldn't activate and the drive would get bus over voltage alarms. I tried turning the adjust screw all the way down but the shunt never activates. So i bought another one. Same thing. Am i missing something or have i just gotten two bad drives in a row now.
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I meant to say bad shunt modules, the drive is fine.
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Hi,
I have an identical drive for a 1.8kW servo used as spindle motor.
If I recall correctly the 050,010,020 and 030 drives are not fitted withe the switch which engages the
brake resistance. Again from memory the braking module for these drives has a switch (MOSFET/IGBT)
inside. If that is the case there is a distinct possibility that a module is faulty and with bad luck two faulty
modules is not impossible either, they are after all right at the business end and come under extreme stress.
I no longer have the manual but it is a free download from Rockwell Automation.
Craig
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Hi,
downloaded the manual and yes they are active. Do you have the line detect terminals populated, I rather think
they will be needed.
How do you feel about opening it up to have a look inside? I fix welding equipment, a lot of inverter stuff, for a living
and am quite used to inspecting/repairing switching circuits both single phase (320VDC Link) and three phase (585VDC Link)
and that's when the manufacturer is not using PFC boost.
If I recall your previous posts that you are Austrailian? Surely we can cooperate to fix it.
Craig
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Definitely have the ac line detect terminals wired. I read the manual too but no mention of what to do if the active light does not come on. They were both cheap so i don't mind opening up to fix.
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Here is the inside
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Hi,
lower right hand corner, the TO247 device, cant read it but guess is a MOSFET or IGBT. Not sure what the IC north
of that, logo =L, whats the part no.?
I would be testing the MOSFET/IGBT and make sure you have continuity through the resistor (the big one top
left).
Craig
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Hi,
have you considered making one? I think a working unit could be done pretty simply.
Craig
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Hi,
something like this.
Rectified and smoothed ACline for DCLink reference voltage. If the DCLink+ goes 24V (zener drop) higher then the opto LED conducts turning the shunt
MOSFET on. Cheap and cheerful gate drive powersupply with a little transformer, rectifier and filter cap.
Craig
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Hi,
that very simple idea might have a few weaknesses. What happens if the ACline voltage disappears while the DCLink holds up for a second or two.....
the LED of the opto looks like it could come under severe reverse bias...not a good look for an LED.
Some refinements are definitely in order. I might try making one to see how it pans out in practice.
Craig
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Hi,
added a couple of diodes, D2 prevents the opto LED of high reverse bias if ACline disappears but DCLink stays up.
D3 prevents massive forward current in the event that ACline is still up when DCLink is down or shorted low.
Craig
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The big round resistor has 306k ohms. The larger igbt in the lower right corner has 11.5 ohms from center to left leg and .5 ohms center to right leg.
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Hi,
don't think those sound right.
The big (main) braking resistor should be about 36 Ohms.
Resistance measurements are not really effective with a MOSFET/IGBT.
You need to use diode check on your multimeter, positive drain (center) negative source (right) should be close to open circuit.
Negative drain (center) to positive source (right) should be the MOSFET body diode, about 450mV.
Would expect drain (center) to gate (left) to be close to open circuit.
Craig
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I just opened up the second one i bought. No wonder it doesn't work, its completely burnt inside. Just can't have nice things.
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Hi,
yeah, these things live at the 'sharp end', if anything is going to go bang its these.
Craig