50 hz 380V 3 Phase Y Config. to 60 hz 208V 3 Phase Delta Congif.?

[hockeychamp297]

Hello,

I have an issue that seems to work in theory just not sure if it is true or not. I have a piece of machinery, (string bowling pinsetter from europe) that has two configurations in it's manual for power. It has wiring diagrams for the machine so it can be wired 380V 3 Phase Y Configuration or 208V 3 Phase Delta Configuration. The electric motors state 380V 3 Phase Y configuration 1/2 hp. The wiring diagram for the 208V Delta configuration states to change a fuse to use on 208V Delta Power. Does anyone have any experience with machines that are wired for equipment like this and could shed some light on this issue?

Thanks,

 

[collies99]

Are the above voltage rating 208V and 380V from the manual at a specified 50 Hz ?

Are you planning to power it up at 60 Hz ? And still maintain the proper volt/hertz ratio ?

The manual is correct that fuse size has to change between 380v to 208v. Full load amps almost double at 208v versus 380v.

 

[hockeychamp297]

Hello Collies,

The manual does not specify the frequency it just has a 380V Y configuration and 208V Delta configuration. From what I understand in the 380V Y configuration it is 3 legs of 230V. In the 208V Delta configuration it is 3 legs of 208V from two 120 volt sources 120 degrees out of phase. If this is correct the Volts/hz ratio will decrease? Which will be ok? I'm assuming the motors will lose some power but they are already geared so I think it will be ok if they lose some power. Does this sound correct?

Thanks,

 

[collies99]

The nameplate on the motor should tell you the design frequency, if European then guess would be 50HZ.

Also check on the Full Load Amps value and if there are 2 ampere rating for the 2 listed voltages.

The motor may already be design with dual frequency in mind since 208v Y is a North American system at 60HZ while 380v Delta is odd for North America and may well be for a Europen rating. If that is the case you can just connect to 208 V as per wiring connections suggested in the manual.

If you can either take a nmaeplate picture or post the relavaent nameplate data it would be priceless since we have to confirm a couple of things first before applying power to it.

 

[waross]

Volts per Hertz at 380V/50Hz = (380/1.73)/50 = 4.39 V/Hz. This if for the windings in star configuration.
Maximum rated voltage at 60 Hz = 4.39 v/Hz x 60 Hz = 263 Volts.
The motor may be connected to 208 Volts, 60 Hertz with no fear of saturation.
If the nameplate shows a 208 Volt, 60 Hertz connection then either the manufacturer has sized the motor to have sufficient power at 208V, 60 Hz, or there is an optional 208V, 60Hz motor.
Check the nameplate on the motor. The motor may have enough power or you may have to change the motor and the fuses.
Not enough information to say which right now.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

Another way of looking at what Bill said:

Must likely your motors are IEC style dual voltage, which means that you connect them in Star for the higher voltage, or Delta for the lower. In their case, if 380V is high, then the lower voltage is 220V 50Hz. So like he said, the V/Hz ratio that the motor is designed for is 4.4 V/Hz. When you connect it at 60Hz, the voltage should be 263V max for that motor. If you exceed that, the windings over saturate and the motor over heats. That will not happen in this case.

But if you apply only 208V 60Hz, you are seriously UNDER fluxing the motor and you will lose torque. Starting torque and peak torque will drop by the square of the change. So it will drop by about 37% in this case, and your running torque will drop by about 21%. If the mfr says that is OK, that means that they know that this loss of torque is not significant to this machine, meaning that they put in a motor that is sufficiently over sized to handle the loss of torque resulting in the voltage/frequency change. But you could connect it at 208V or 240V, it will be fine either way, as long as you use the Delta connection pattern inside of the motor peckerhead.

"Will work for (the memory of) salami"

 

[waross]

What Jeff said!!
Thanks for the additional clarification Jeff.

Bill
--------------------
"Why not the best?"
Jimmy Carter