Hello, I have an old Bridgeport J head with a 2hp 3 phase motor. I want to use a VFD for speed control as well as for ON/OFF and FWD/REV. Do any of you have any suggestions on what brand/type works best for this application?

Thanks,
Scott

I use a Hitachi SJ200-015 with that same size motor. You'll need a braking resistor, unless you like 10 second accel/de-accel ramps. I used a 120 volt 300 watt (50 ohm) car block heater - works great...


You can buy the Hitachi and others from www.driveswarehouse.com...

Thanks, that's the one I was considering, called driveswharehouse and they confirmed it as well. I asked them about a braking resistor, they quoted me an additional 181.00:eek: is there anything else I can use that may look a little less, well like a block heater?:D

Scott

Would a 97 ohm 300 watt braking resistor work? does it have to be exactly 300 watts and 50 ohms?

Is that just a resistor or do they call out a braking unit or something, I don't know if it is that easy on that drive......not at all sure tho....

I too am using the Hitachi. Works great but dont find the need for a resistor. What am i missing?

I use a Hitachi SJ200-015 with that same size motor. You'll need a braking resistor, unless you like 10 second accel/de-accel ramps. I used a 120 volt 300 watt (50 ohm) car block heater - works great...


You can buy the Hitachi and others from www.driveswarehouse.com...

Do you have that plugged into the bottom of your coolant tank?????

archie =) =) =)

Would a 97 ohm 300 watt braking resistor work? does it have to be exactly 300 watts and 50 ohms?

It would work but it it won't provided a whole lot of braking torque. The minimum (for the 015) is 35 ohms... I choose 50 'cos that's what I had.
there is a table in the user manual that shows the relationship between resistance and braking torque.

The high wattage just helps with the duty cycte. Again, there is a table that show that relationship.

Is that just a resistor or do they call out a braking unit or something, I don't know if it is that easy on that drive......not at all sure tho....



That drive has a braking unit built inside. So yes, it's that simple. The OEM resistor has a Nema cage and a thermal cutout, but they are expensive.

I too am using the Hitachi. Works great but dont find the need for a resistor. What am i missing?

If you accept longish ramp down and up times, you generally won't need it. I like the precision of a short start/stop cycle.

It also depends on your motor size and construction. My US Motor 2hp really kicks out the voltage (386 or so... ) when it turns into a generator!

Thanks, that's the one I was considering, called driveswharehouse and they confirmed it as well. I asked them about a braking resistor, they quoted me an additional 181.00:eek: is there anything else I can use that may look a little less, well like a block heater?:D

Scott

$181 - that's just for one, and you'll likely need THREE for high performance braking!


Search ebay for "OHMITE" or "POWER RESISTOR" etc... many many surplus high wattage resistors available from $3 to few 10's. Slap in a high wattage device and you can forget about the thermal cutout etc. make sure it's vented and protected from chips. I prefer a separate compartment from the controller for that type of resistor. My "block heater" is connected via thermal grease to a heatsink in the top of the enclosure.


300-400 watt 120v "anything" will work well as a braking resistor (check your drives' minimum resistance)... coffee pot heater... etc;)



Here's one of my installations.

http://s238.photobucket.com/albums/ff150/lakeside53/BP%20VFD/

The "block heater" is attached to the slab of aluminum plate in the top of the enclosure. Also... I modified the motor so it had a fan switched by the VFD relay contact (to provide cooling air even at low motor speeds).

The big black contactor is so I have a front pane; "one switch" power disconnect for the 220 and the 4 120 volts plugs in the bottom of the enclosure.

Thanks for all the info lakeside, I didn't realize that the resistors are as large as they are. After doing some research, I think the block heater is a neet idea. Do you happen to recall the brand and model, I'm having trouble finding a 300 watt. The guy at drives wharehouse told me that the minimum for ohms for this model is 50 BTW.

Scott

Yes, it's this one... more expensive than I thought!

http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200339107_200339107

I bought 2 at a garage sale for $5 (total) ;)



You could buiy a pair of these - place in parallel for 50 ohms - that would rock!

http://cgi.ebay.com/Ohmite-Power-Resistor-160W-100-Ohms-Aluminum-Housing_W0QQitemZ330257548888QQihZ014QQcategoryZ4664QQssPageNameZWDVWQQrdZ1QQcmdZViewItem



or


Even cheaper and better - two of these in series : http://cgi.ebay.com/POWER-RESISTOR-DALE-24-9-OHM-1-100-Watts-E586_W0QQitemZ330109537870QQihZ014QQcategoryZ4664QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247


This guy has many big power resistors : http://stores.ebay.com/SAN-FRANCISCO-SURPLUS.

The power dissipated realy depends on your duty cycle... go big and "forget it". Just make sure you program your VFD registers that track the braking usage to "100% (or whatever you want).


BTW... download the owners manuals for the drive you want to buy. Mine says 35 ohms.

Great Lakeside, I bought the pair of millitary surplus ones you listed, you are correct about the 35 ohms BTW, I got my inverter today and the manual clearly states 35 min.;)

Scott