rogersmithiii

Can someone offer a bit of education please?

We have a three phase, 220, 3 hsp electric motor that we need to run off of single phase 220. We purchased an appropriately sized variable frequency drive from GE to run this unit. We were told that this drive would do the phase conversion for us. Inside the cabinet of the equipment, there is a motor, along with three thermal overload relays, and a 220 v contactor.

When we depress the momentary contact start button on the motor, the contactor chatters, and arcs like crazy. Eventually (maybe 3 seconds), the motor will start.

Three questions.

1. The drive mfger tells us that the output from the drive is not real sine wave AC. Should the output from the VFD be able to cleanly close a 220 V contactor? Is it that we might have a bad contactor, or is it that the contactor won't close with the voltage output from the VFD?

2. The drive manufacturer tells us that the drive is essentially doing the power switching to the motor, and that we could probably remove the contactor. We called the equipment manufacturer and asked them, and they appeared to have a coronary. They started screaming about safety issues, and dead workers, and liability issues, and told us that we needed to buy a new $2500 motor from them to fix our problem. They would not give us any info about how all of this works.

Is the drive manufacturer right? Can we remove the contactor because the VF drive is switching the 220 for us?

3. There are three thermal overload relays in this unit. Will they be OK if we drive this unit with the VFD?

Any information would be appreciated.

Rog

JayH

I recommend an electrician examine your installation.

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vanvincent218

had an application where we were to install a 3 phase compressor motor in a mechanic garage. Butt there was only single phase..after exploring all the options. it was cheaper to just switch the motor...it sounds like whoever sold you this stuff wasnt totally informed of its application. I would implore you to call a licenced electrician and have him rethink your set up.! hope the warrenties are still good!
good luck!

rogersmithiii

The problem was that the VFC wasn't compatible with the contactor. Removed the contactor and the thermal overload relays (the tasks of which are now handled by the VFC), and everything works ducky. Found some top notch techy guys at a major electric motor company, and the company that made the VFC, and they provided the necessary details.

Thanks
Rog

varmit

A contactor on the load side of a VFD is a BAD idea. On some drives, if a load side contactor opens with the motor running, that can be the end of the drive. This also applies to places that want to use twistlocks at motors. Most newer drives will protect themselves from this problem, but I have replaced several older drives killed by this.

If you need/ are required to have a "e-stop" contactor, install it on the line side of the drive.

pudge565

Does this also apply to the OCPD (heaters) for the motor? Should they be put on the line side? I ask because I am installing an Allen-Bradley Bulletin 1332 as a senior project. Feel free to PM me for more information.

varmit

There is no reason to install a standard overload block down stream of a VFD.
The VFD has electronic overload protection built in. It is a matter of setting the motor full load amps in the correct drive parameter.

In the "early days" of VFDs, some companies insisted on an O/L block on the load side of drives. This was mainly because of misguided lack of trust in electronic O/Ls of the day. Remember, this was a time of melting O/L "heaters" and dash pots. When an O/L was installed on the load side, of a drive, the O/L relay NC contact was wired to a dive enable input or a drive stop. The O/L does not break the power leads.

Hope this helps.

varmit

My mistake for the day:

I forgot that an AB-1332 does not have an electronic O/L in it's firmware. So you WOULD need an external O/L. Terminals 14 and 15 can be used for this purpose. Wire these terminals to the NC contact on the O/L block. These terminals serve as an "enable" for the drive.

Where did you find a 1332? They have not been manufactured since 1988.

Good luck on your project.

John Valdes

Good job varmit!

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If your not getting old, you're dead.
Tom Petty

pudge565

I don't know where we got them. They have been laying around in the shop for who knows how long. They were probably donated to the school. So if i understand you correctly I take a wire from terminal 14 to one side of the NC contact and from the other side of the contact to terminal 15. I then wire the OL with L1 L2 and L3 and T1 T2 and T3.

MDShunk

A VFD can often be a fantastic and cost saving option when running smaller 3-phase motors on a single phase service. The last one I did was for a second hand 3-phase Hobart dough mixer at a pizza shop. It was cheaper for me to install a VFD than it was to buy a phase converter for this machine. Changing the motor was not an option, since it's somewhat of a special motor for a dough mixer. I have a friend that has an old Bridgeport milling machine in his garage that he runs off a VFD also. He uses it for most of the speed control so that he doesn't have to mess with changing the belting around so much.

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varmit

You are correct on the control wiring of the O/L. For the drive output-T1, T2, T3, would go to the line side of the O/L. From the load side of the O/L, continue on to your motor.

A 1332 is a simple and durable drive. I replaced two of them at a chemical plant two years ago that had been in service about 20 years.

pudge565

Ok thank you so much for the help. I have a thread started somewhere with pics of the begginings of the project. If you want more information on it let me know but I don't want to hijackthis thread.

p_logix

Expect nuisance network communication faults when installed on the line side. Operator hits a e-stop for a second and the drive starts to power down than they restart.

Unless you power the drive with external power to maintain network comms. E-stop on the line side could be a big problem for some.

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p_logix
"Meggers Don't Lie, Electricians Lie". Go LAKERS!!!!

varmit

True, if you have drives on a network, however few places even require a contactor any more. Most drives, other than Seimens, do not have the capability for separate control power. I would normally only break the drive enable circuit through the E-stop. If the operator is using the E-stop, for a normal machine stop, someone needs some training. If there is a REAL need for an E-stop, faulting the network would be a minor problem.

p_logix

We use AB powerflex 70's and when a e-stop/safety is pushed bus voltage drops but the Ethernet IP 20 commE module maintains communications and HIM continues to stay lit. Ethernet IP takes some time to establish communications. Contactor is on the line side this method works great for this app.

Another situation we had AB 1305 Drives configured for remote I/O AKA "Blue hose" and some Powerflex 70s with a 20commR module that also had E-stop contactors on the line side and we had a lot of "Undervoltage Faults" magically appearing. Operator hit a E-stop finished picking up down product after reaching in to machine and restarted.The drive never fully shutdown/discharged. Auto reset function did not solve this problem. These contactors have been moved to the load side, no more problems. Not one of these drives have failed.

Well not if you are the electrician who has to go reset the VFD/panel.

Minor problem? Tell that to management or the corporate bean counters. Especially when they are having their morning production meeting and reviewing shift issues, downtime, and all faults on their central reporting program only to see EthernetFault, EthernetFault, EthernetFault, EthernetFault, EthernetFault, EthernetFault, Ethernet Fault, Ethernet Fault.............up the

I agree a machine cycle stop should be used for a normal shutdown. However in the "real world" operators hit e-stops to "reset" because they simply can't figure out why certain conveyors won't run or a machine will not start. Then the Electrician is called out and 20 VFDs are faulted because the contactor is on the line side of the Drive. There is a reason they are the "operator".

Not all places use applications where they are sending ones and zeros through a communication cable. But when they are the Drive must be set up/configured/wired to operate safely and most importantly to production personnel, minimize downtime as much as possible.

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p_logix
"Meggers Don't Lie, Electricians Lie". Go LAKERS!!!!

varmit

As I stated previously, most of the newer drives will self protect against damage if there is a load loss (contactor opens) while running. It is mainly a problem with older versions.

rogersmithiii

Thanks for all of your input. Being able to use a $186 drive instead of a $800 rotary converter was a great discovery. The whole experience also gave me a great education on 3 phase motors, drives, contactors and other related issues.

The mfg of the equipment was not helpful. GE was pretty helpful, but the guy who really provided the greatest amount of info was the Marathon Motor Rep. Knew his stuff, and did a great job of explaining things. And of course, everyone here was mucho helpful too.

Rog

John Valdes

I never use contactors on either the line or load side of the control. Sometimes the SOP for the facility will require the contactor. However, if they trust the installer/tech they will listen and allow just a disconnect ahead of the drive.

I do not like using the enable input either. If you are using braking it will coast instead of brake to stop. I use the stop input. That way I can control the stop.
Maybe the newer controls have addressed this issue. It has been 5 years since I have dealt with any controllers.

__________________
If your not getting old, you're dead.
Tom Petty

varmit

Yes, opening the enable loop will initiate a coast to stop and this can be a problem in some applications- some machine tools for example. I try not to have any absolute rules, just preferences for control logic. Most applications are unique and require a certain amount of customization for safe and efficient function.