Overload relay keeps tripping.

[rdhem2]

As a retired electrician wannabe machinist all I can politely say is all those phase converters and static units are obsolete pieces of s--t. VFD is the only way to go as they offer overload protection, and direction control as mentioned but so much more. 1 phase to 3 phase conversion to 5 hp is the largest I ever installed for 240v rated motors. Also infinate speed control from 0 to name plate rating. Under voltage/over voltage protection, phase failure protection, your motor never had it so nice. Preset speeds can be set up via switches for different operations. Ramp up to speed time curve for gentle start ups and ramp down time curves for a nice easy stop.

Now the down side, these VFD's use very high voltages and frequencies to do their job. Old, older motors have insulation for the windings that is not rated for this use. Most motors will stand up in my experience, but early failure is also possible but slight. Operating the drive in constantly below 25-30 Hz is not generally recommended as the cooling fan on the motor is less efficient and the motor will overheat from thermal problems, not electrical problems. If you must operate at that speed, gear it down.

All things weighed out, the Variable Frequency Drive is the way to go. These come in two basic styles, constant torque, and constant horse power, tell the salesman you want one for conveyor duty (constant torque), or fan duty (constant horsepower). Lathes, mills, drills, etc utilize the constant torque version as the load is variable. Fan duty the load is constant. You have reached the limit of my talents but I believe by experience I am correct. :thumbzup:

 

[Brandon]

The VFD is the way I'm heading. As for what Pacer said, I'm am running a 3hp phase converter on a 3hp motor. The way I figure, if the motor is kaput, I'm still going to need a way to control the new motor. I was considering a RPC so that I would also be able to run my mill. That being said, I can buy 2 VFD's for the price that I will end up paying for a idler motor for a RPC. On top of that, I would have reverse and variable speeds on my mill. The tricky part will be the Gorton's feed motor, but that hill will be climbed after I start making chips with the lathe...
Thanks again.

 

[rdhem2]

Brandon;
Here is a crazy idea my man. If the motors are close to the same amperage rating why not buy one VFD and put a plug on it (female) and plugs on each machine (male) so they can only couple to each other. Chances are you don't run both at once anyway so just do the old switcheroo and get by with one VFD until you can get a second? Remember to size for the larger of the two loads if you do. A small differance in amperage is not that critical. This is only really important if you run at full load for long periods of time. Continous duty is rated at something that operates for periods of four hours or longer at a time. HTH. :LOL:

 

[strantor]

Brandon;
Here is a crazy idea my man. If the motors are close to the same amperage rating why not buy one VFD and put a plug on it (female) and plugs on each machine (male) so they can only couple to each other. Chances are you don't run both at once anyway so just do the old switcheroo and get by with one VFD until you can get a second? Remember to size for the larger of the two loads if you do. A small differance in amperage is not that critical. This is only really important if you run at full load for long periods of time. Continous duty is rated at something that operates for periods of four hours or longer at a time. HTH. :LOL:

you could do that, but you'd have to re-enter the motor nameplate parameters and/or autotune the drive every time you swap over.

 

[Pacer]

you could do that, but you'd have to re-enter the motor nameplate parameters and/or autotune the drive every time you swap over.

While I have nothing to back it up, it seems that perhaps the VFDs arent especially sensitive to this - say two 2hp motors or a 2hp & a 1 1/2hp with similar amp requirements (which many of the 3ph motors are) I say this because I am seeing this written about being done more and more. In my own case I have bought 3 different machines - 2 lathes with a 1hp and a 1 1/2hp, and a mill with a 2hp - and used my existing mill 2hp VFD to run them off an extension cord for testing/demonstrating with out any hint of a problem.

 

[strantor]

While I have nothing to back it up, it seems that perhaps the VFDs arent especially sensitive to this - say two 2hp motors or a 2hp & a 1 1/2hp with similar amp requirements (which many of the 3ph motors are) I say this because I am seeing this written about being done more and more. In my own case I have bought 3 different machines - 2 lathes with a 1hp and a 1 1/2hp, and a mill with a 2hp - and used my existing mill 2hp VFD to run them off an extension cord for testing/demonstrating with out any hint of a problem.

I also can't exactly back it up. I've never tried swapping different motors of different ratings without entering nameplate data and autotuning. For all I know, it could work just fine on the fly like that. However, I have set up a lot of VFDs on a lot of motors, and read a lot of *caution: _____*, *warning______*, and *note:_______* in VFD manuals that contributes to what I'm saying. If those features and parameters were not important, they would not be part of the VFD. The VFD needs to know specific things about the motor that it's controlling, like inductance, resistance, etc. Different motors of the same model, manufacturer, and production batch can different inductances. Inductance limits how fast current can rise. VFD needs to know fast current can rise in the specific motor, or else it could overshoot and kill the IGBTs. - that's just the one example I can think of ATM, I'm sure there are more good reasons.

 

[Brandon]

UPS just dropped off my new Teco VFD, I slapped it on real quick and it works awesome. All three legs are pulling 6 amps and the motor is happily humming away. Now all I have to do is hook it up right and make it all look pretty.

:ups:
Thanks again to everyone.