Need Help!- Hitachi SJ200-015NFU2 braking question

[arvidj]

As the title implies I have a Hitachi SJ200-015NFU2. I also have two 33 ohm 150 watt resistors that I want to use for braking.

Page 2-8 of the manual suggests that the braking resistor goes between the + terminal and the RB terminal. Page 2-20 shows these terminal with the + terminal having a jumper to the +1 termina.

I am assuming that I can put the two resistors in series for a total of 66 ohms and then attach them to the + and RB terminals and be good-to-go. I thought I saw that the Hitachi braking resistors were in the 50 ohm range so I also assumed that 66 ohms would be close enough and would error on the conservative side.

Does anyone care to comment on this plan? Good? Bad? Lost my mind?

Thanks,
Arvid

[Karl_T]

That's the right place to connect. Double check, but IIRC the resistor value is quite a bit lower than 66 ohms. There's a table in the manual. You'll get overvoltage alarms with too high a resistance.

Karl

[thosj]

When installing one of these braking resistors in an SJ200-15NFU2, are there any parameters that need to be set or does it just work?

Reading the manual, B090 and B095 might be suspects!

Right now, without the resistor, mine takes 15 seconds to haul my BP clone CNC mill down from 4300 rpms. If I set parameter F003 (decel) lower than 15, I get an over voltage E07 error. I've set B090 to 75% and tried 25% and 50% and I've set B095 to 01 On at RUN and 02 ON, to no effect, so I'm thinking I need a brake resistor. Question is do I also still need these parameters and what to set them to.

Thanks,
Tom

[thosj]

Just for anyone finding this in a search:

I bought a Hitachi JRB120-3 resistor from driveswarehouse.com. $85, not cheep, but it does the job.

I connected to RB and + terminals. The jumper remains that was factory installed. The two small wires on the JRB120-3 were not connected to anything. I think they are for sensing.

I set parameter B090 to 75%, just winging something. I set B095 to 2, ON.

Works fine. I set F003, deceleration time in seconds to 2.5. It will stop the BP spindle from 4500 RPM to stopped in that 2.5 seconds and the resistor gets warm but barely. I could probably set decel lower, but it seems OK now, WAY, way better than the 15 seconds I was getting and if I tried to stop faster, F003 lower than 15, it would E07 overvolt error, l guess from generating back.

Anyway, works great with resistor. Gets cost of SJ200-015NFU2 up to around $400 tho'.

[boilerbots]

I believe the two other wires are for temperature sensing. Keeps the drive from over heating the resistor from to much breaking.

[thosj]

Originally Posted by boilerbots I believe the two other wires are for temperature sensing. Keeps the drive from over heating the resistor from to much breaking.

OK, where do they connect? The included documentation seems to show them attaching to some external something, perhaps a temp display(?), not to the drive itself. I would love to know if they connect to the drive to keep it from overheating, and where on the drive

[TOTALLYRC]

Did you get an ohm reading on the resistor??

Thanks,
Mike

[thosj]

Get an OHM reading? I didn't put an meter on it, I trusted the label/order info. 50 Ohm, 120 watt. Should I put a meter on it and actually TEST it? It works fine, so I'm guessing NOT. It gets warm to the touch slamming the spindle to a stop from 4400 rpms in 2.5 secconds, a couple times in succession, but not HOT. The 4400 is on the overdriven pulley on my BP clone, ~3500 motor, 5560 spindle, top, at 120Hz on the drive, wired to the 4 pole terminals on the motor.

Or if you're just looking to see what the resistance is so you can go somewhere and just buy an equilivant resistor, well, then 50 Ohm!! It's pretty big, maybe 1 3/4 wide by 6 3/4 long by 3/4 thick, alum case with the back some sort of imbedding medium. It doesn't heatsink to the mounting spot on back, it's not flat alum but the imbedding stuff. I just screwed it to the inside of spindle control box I have the drive in.

[TOTALLYRC]

Originally Posted by thosj Get an OHM reading? I didn't put an meter on it, I trusted the label/order info. 50 Ohm, 120 watt. Should I put a meter on it and actually TEST it? It works fine, so I'm guessing NOT. It gets warm to the touch slamming the spindle to a stop from 4400 rpms in 2.5 secconds, a couple times in succession, but not HOT. The 4400 is on the overdriven pulley on my BP clone, ~3500 motor, 5560 spindle, top, at 120Hz on the drive, wired to the 4 pole terminals on the motor. Or if you're just looking to see what the resistance is so you can go somewhere and just buy an equilivant resistor, well, then 50 Ohm!! It's pretty big, maybe 1 3/4 wide by 6 3/4 long by 3/4 thick, alum case with the back some sort of imbedding medium. It doesn't heatsink to the mounting spot on back, it's not flat alum but the imbedding stuff. I just screwed it to the inside of spindle control box I have the drive in.

I have some large resistors here and yes I was wondering if I could use what I have instead of paying $80 for the factory one.

Sorry if I upset you.

Mike

[thosj]

Nowhere NEAR upset! Just wondering if I'd missed something not checking the actual resistance. I think you COULD use any resistor, long as it was big enough, watt wise, to dump the heat. The docs DO show using two of these in parallel, too, just for your info.

Tom

[boilerbots]

Originally Posted by thosj OK, where do they connect? The included documentation seems to show them attaching to some external something, perhaps a temp display(?), not to the drive itself. I would love to know if they connect to the drive to keep it from overheating, and where on the drive

Good question. I can't find any explanation as to what those extra two connections are for. Maybe you can put an Ohm meter on them and see if they are isolated or common with the other leads. If they are isolated and have a decent amount of resistance then it is most likely a thermistor (temperature resistor). You can test this by running and braking to heat the resistor and see if the resistance changes.

The other option is that it is a sort of alarm output. The description of the device says it has a relay that protects from over temperature situations. Perhaps these wires are also connected to this relay and can be used to generate an alarm signal to the inverter. The inverter would not have any other way of knowing this device was open circuit except that it's DC bus power does not get disapated during braking and thus goes overvoltage and shuts down to protect itself.

For those asking about resistors, the specs say 200W at 100 ohms, so there are your specs. The drive internally has a high voltage DC bus somewhere around 300V and when you try to stop the motor it is regenerating power back into this DC bus. That power has no place to go and has to be burnt off through some resistance.

The cheapest option is to enable DC braking. In this mode you are using the resistance of the motor to burn off some of that power and also creating a magnetic field that helps stop the motor. This is all I use on my Wells Index CNC mill and it works most of the time. It is only a problem sometimes when going from max 4400 down to zero rpms, but smaller changes are pretty good. You have to play with the limits of when it kicks in and for how long.

[boilerbots]

I should amend what I just said about the DC braking on my Wells Index. It does work and can make a difference as opposed to not enabling it. I can not remember the limits to how good it was, I forgot that ultimately I made a mechanical brake for the spindle.

My Wells Index had a mechanical brake on the spindle motor shaft that was a simple on-off motor brake and was controlled by the 3 phase power that also went to the motor. Simple magnetic brake thing.

I couldn't use it because I was not running the spindle from the SJ200 VFD. Although deceleration was working OK, it can not hold the spindle in a "locked" position at zero RPMs for changing tools. I have a quick change adapter on the spindle, so the spindle needs to be held tight to make changes "quick".

Ultimately what I did was to remove the electro magnetic guts from the motor brake and externally mount air cylinders. Now the SJ200 braking output signal controls the air valve that actuates the motor brake. This has been working good for me over the past year, except for the occasion where I forget to turn on the shop air!

I mentioned this pneumatic brake idea to the motor brake manufacture, they have been in this business for something like 100 years and they never had a product like this.... seems like I gave them a free idea. The nice thing about this, in my opinion, is that it works independent of your machines voltage, all you need is the correct air valve to match your controllers voltage.