Using 400V 50Hz 3 phase motors with 240V single phase 60Hz

[Planobilly]

Hi,

We have a machine from Europe with three 400V 50Hz 3 phase motors. Assume we only have 240V single phase available. There may be 480V single phase available. I don't currently know how many poles the motors have. Assume they are not made for both 50Hz and 60Hz as some are. Power consumption is 2.95 kW. The application is a agro potting machine. The load on the machine is fairly constant. The machine puts potting soil into pots and drills a hole in the potting soil and moves the pots on a conveyor.

I have a rotary phase converter on another potting machine machine which has 240V 3 phase motors which works well. This potting machine was made for the US market.

I have never been involved with using a VFD. They seem at first glance to be pretty complex with lots of possible problems from supply power issues.

I also have not seen the schematic for the control panel on the machine which I assume has Siemens speed controllers for the 400V motors. Where I am going with that is considering replacing the three motors but I don't currently know the implications of running 240V 3 phase to the machine panel and what else I would likely have to change. The three phase 240V induction motors that I would need are not expensive, likely less than one thousand dollars.. I assume all the relays, speed controllers and other panel components would have been designed to run on 400V 50Hz so until I see the schematics there is no way to know how problematic that sort of change would be.

My only real question at the moment is do you think a VFD is a viable solution to the issue?

Thanks,

Billy

 

[wirenut]

If you go the motor change route, you will need to change the control transformer (most controls are 24v) or the primary taps on it. You can check the coil voltage on a control relay without the schematic. Most machines I've worked on (including ones from germany, italy, and the netherlands) have 24vac controls.
The wiring diagram will usually tell you what to connect to what for a given primary voltage.
The VFD route can get pricey- you will need one that puts out 400v- not real common in the US, especially if you are feeding it with single phase and running 3 phase motors.

Bottom line you will have to calculate the cost of motors, control xfmr(s) (if necessary) and the labor to change it all, VS the cost of a VFD large enough to run the machine.
VFD = easiest , but most likely costliest. New motors = labor intensive, but possibly cheaper.

 

[Planobilly]

Thanks Wirenut,

Just the kind of feedback I was looking for. I assumed more or less what you stated about a VDF that puts out 400V not being real common plus the single phase to three phase issue.

I got a bit more info today and the controls are 24V. The motors are 50/60.

There is one other issue with changing the motors. The flanges are metric. I am not sure how much of an issue that will be. The MFG Javo would likely have flanges for US motors as they sell the same machine here. I will have the schematic tomorrow and start putting some numbers together.

Thank you very much,

Billy

 

[wirenut]

If you have any questions, feel free to message me. I will be out of town the rest of the week, but will try to look in from time to time.

 

[Planobilly]

Thank a lot for taking the time to respond. It is unlikely a decision will be made before next week. There are some other mechanical issues I have to solve also. One of the devices that moves the pots off the conveyer is numatic on this machine. With the high humidity here in south Florida that sort of system is always problematic.

Thanks,

Billy

 

[wirenut]

Google "silica gel compressed air dryer"

 

[Planobilly]

Will do...thanks

Billy

 

[Tom.G]

With the high humidity here in south Florida that sort of system is always problematic.

The larger air usage facilities use an active "air dryer." This is a refrigerant based system, compressor, heat exchangers, Freon or equivalent refrigerant. Another partial solution is put a commercial timed valve on the drain of the compressor tank. This periodically (5 secs. every half hour, programmable) drains the condensate from the pressure tank.

 

[wirenut]

I was going to suggest an air dryer, but figured the added electric would be too expensive, and was not sure if the unit could be used for just one machine.
I forgot about the timer/valve.
Those are also good suggestions.

 

[CalcNerd]

Nearly all VFDs offer single phase input and can be configured to provide 50 or 60 or more Hz output. Most also have a voltage cutoff that you should be able to program, but you may have to ask all prospective vendors/suppliers. One problem is your service feed for the VFD might be severely undersized as your input voltage /power is based upon 240 volts single phase and these motors are 3 phase and nearly 2x the voltage. Therefore they will draw 1.7*2*full load of current to calculate the current draw at the lower voltage ie rough sample calculation: if the current motor(s) need 20 amps at 400V 3 ph, they will need to be fed from a panel that can spare or provide 68 Amps plus some overhead for initial starting current.

 

[Planobilly]

Hi guys,

I think a timer valve will most likely be the answer to the air issue.

I had a chance to look at the machine today and the motors are 50/60HZ. The 24V transformer also has a 230 volt tap. It looks like all we will need is a phase converter.
I was told originally the motors were 400V 50Hz. Anyway, that makes things less of an issue to deal with.

Thanks for all the help,

Billy

 

[jim hardy]

I don't currently know how many poles the motors have. Assume they are not made for both 50Hz and 60Hz as some are. Power consumption is 2.95 kW. The application is a agro potting machine. The load on the machine is fairly constant. The machine puts potting soil into pots and drills a hole in the potting soil and moves the pots on a conveyor.

How are they connected to the machine? Belt drive?
Nameplate on motors: 2.95kW each or total for all 3?
What RPM ? RPM will be a little below synchronous for # poles, 2 pole :: 3000 RPM, 4 pole ::1500 RPM, 6 pole ::1000RPM,
8 pole::750RPM and so on

My only real question at the moment is do you think a VFD is a viable solution to the issue?

I don't see why not.

A couple experiments to see if you can simplify..

The motors will start and run on 240 3 phase 60 hz from a converter if they're unloaded.
You might check that with the motors disconnected from machine, can you take off a drive belt and use your existing converter for a test ? Two questions arise, though,
1. They'll try to run at 6/5 normal speed . If they're very lightly loaded they'll make it . If heavily loaded they will fail to make speed, will draw starting current continuously and burn up.
At half volts you'd only get 25% torque and i seriously doubt they oversized the motors 400%
so i don't think running them on the machine at reduced voltage will work at all.

400V 50 hz is same flux as 480V 60 hz and the motors should be pretty happy with that.
So you should get 480 volts in there and a 480V rotary converter.
Or, open one of those motors and see if it can be rewired for low voltage. A 200 V 50 hz motor ought to be happy with 240V/60hz. It's that old "Volts per hz" ratio...
Then another converter like you already have should handle your motors.

2. Since the motors will run 20% too fast over here, the machine will really go and presumably take more shaft horsepower.
If the motors are belted to the machine can you change a pulley diameter someplace, or a couple gears to slow it back down ? ( In my day we used Alan Arch at Southern Gear, NW 106 St and railroad tracks near 37 ave on North end of Hialeah to solve gear troubles. )

I have a rotary phase converter on another potting machine machine which has 240V 3 phase motors which works well.

If your motors can be wired for 200V/50hz, give 240/60hz a try.

That leaves the control panel.. You'll have to hand it 400 volts, or change its internal transformers and maybe power supplies. Computers in it will probably have SMPS's that accept a wide input range. Lots of inspection to do, but you know what to look for.old jim

 

[Planobilly]

Thanks Jim,

After looking at the motors, they are designed to run 230V delta 50Hz, 400V Y 50Hz, 267V delta 60Hz, 480V Y 60Hz. And yes, I can get 480V one way or the other. I have not looked into the availability of a 480V phase converter yet.

A little background is in order. One of my best friends who I fish will all the time owns a plant nursery. I helped him acquire a new Javo potting machine. I installed the machine and set up the rotary phase converter and instructed his men on how to operate it, in Spanish no less! The language issue was the hardest part..lol I also keep the machine running for him.

One of the nearby nurseries acquired the machine in question from Holland. I sort of got pulled into the project at the last minute and to tell the truth only to do a favor for my fishing buddy Carlos. The owner of the machine knows absolutely nothing about pottings machines or machines in general for that matter. The owner had given me a good bit of incorrect information in the beginning. It has been sort of difficult dealing with someone who you have real way to communicate with. To make matters worse he had hired an electrician before he met me who did not know much about the issues. The electrician is telling him one thing and I am telling him something else. Not good...lol

I have all the issues sorted out now that I have seen the machine and been able to look at the data plates on the motors and the transformer for the 24V supply. So, thanks to everyone who has put me up to speed on these issues.

Here in the United States there are still way too many people who have no idea that the rest of the world does not function in the exact same way as here. No, the measurements are not in feet, no it is not the same voltage, no the instructions are not always written in English, no not everyone drives on the same side of the road, and yes you can get a Big Mac in Paris but you have to speak French...lol

Thanks guys,

Billy

 

[jim hardy]

is your incoming "230" really 230 or closer to 240? Might be in the 250's and within distribution tolerance.
Anyhow, think this through... check me

Motor's Torque is in proportion to square of voltage.
Wiring one for 267 and handing it 230 will multiply its speed-torque curve by (230/267)² = 0.74
Meaning if you load it with normal torque at reduced voltage it'll draw more current and might burn up.

But you need a speed reducer between motor and machine because of the 60hz/50hz conundrum. That'll lower torque demanded of motor which helps you. You need ratio of 60hz/50hz to match speed. That's 1.2 or 0.83 depending if you call it 6/5 or 5/6.

Changing a pulley to lower machine speed to 0.74 will lower torque demanded of motor by about same proportion, so it should run at same spot on speed torque curve. Meaning run current will be about normal even with the lower voltage. So windings in motor should be happy.
At reduced voltage of 230/267 = 0.86 your iron loss will be way down making the stator happy.
Motor's Peak Torque will be only 0.74 what it should but you get that back through the speed reducer so machine should be happy.
Speed reduction to .74 is more than you need to match speed, you need only 50hz/60hz = .83 so machine will be a little slower. That might be a good thing for the tropics down there ?

Summary:
If you reduce pulley size a little more than you need, so as to match torque demanded of motor to reduced voltage motor capability curve, and accept 9% slower run you should be able keep everything 230 volts.
At least the numbers say that.
Can you wire up a machine and see how much current it draws ?
If it does okay without speed reducer and operators can keep up with it you have it made...

Or is it easier to bring in 480 ?

old jim

 

[Planobilly]

Hi Jim,
The three motors drive,

Motor One... the drill ( drills a hole in the soil to put the plant in) which is low torque and not very speed sensitive and direct drive but having it run too fast will sling soil out of the pot

Motor Two... drives the potting soil conveyor belt at the bottom of the potting soil hopper and is connected by agear box. The torque will change with loading condition of the soil. The speed of this conveyor belt is mechanically controlled by a adjustable ratchet engaging a gear ( not a great deal of speed adjustment control). This motor need to turn at close to design speed.

Motor Three...drives a round "squirrel cage" elevator device which takes soil off the potting soil conveyor and drops it into the pots. The speed of this motor has to match the output speed of the soil conveyor. This motor also drives a chain connected to the pot rack that moves the pots on and off the machine through a automatic pot placement device which is synchronized to the speed of the pot rack. In addition, a pneumatic pot take off device removes the pots from the pot rack which also is synchronized to the pot rack.

Bottom line...there are several inter related and synchronized functions that the motors must perform and the mechanical adjustments to these functions are very limited. These adjustments are only designed to deal with soil moisture content conditions and different pot sizes and to some extent the total speed things move through the system.

Real bottom line...the motors need to run very close to their rated RPM and torque values.

As I see it, there are only two solutions. One, produce 400V 50Hz three phase power, or two, produce 480V 60Hz y three phase power. Well..one could also replace the motors to run on 220 ( actually 236V )three phase.

The "normal" voltage" at my friends farm is 236V ( a few blocks away from the machine we are talking about). I have never put a recording volt meter on the line to see what it does over time. We have run our machine for over a year under these conditions without issue. If the voltage would have been dropping from the 236V I would expect to be seeing motors overheat. I check them every time I go there.

Cheers,

Billy