ptonsparky
Tom
- Occupation
- EC - retired
Thank you. Its nice to have company occasionally.
Star Delta troubleshooting
- Thread starter Electromatic
- Start date
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
So you have a 400V 3phase machine and a 240v single phase source with a phase converter? Why is it working at all?
ptonsparky
Tom
- Occupation
- EC - retired
IDK...are 400v motors dual voltage? It was pointed out to me that this is 240 operation. +-
Post 6.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Not if you want to use Star-Delta starting. The dual voltage motors are connected in Star for 400V or Delta for 240V.
MTW
Senior Member
- Location
- SE Michigan
I used to have a customer that had moulding cutting machines made in Germany, they had 6 spindles per machine all direct drive. They were all 230/460V IEC 12 lead motors. They used wye delta starting on all of them. To change voltages, all of the IEC motor contactors and overloads needed to be replaced to be compatible with the change in current.
All of the machines were built for 230V, but later converted to 460V to move to a different facility.
Good thing we got them changed out before Klockner Moller sold off their controls line.
I think the ones your thinking of, 230/400V must be 6 lead motors.
You can use Y-D on both voltages if it’s a 12 lead motor.
Electromatic
Senior Member
- Location
- Virginia
- Occupation
- Master Electrician
I still have much to learn on motor math, though I have been studying some winding topology. Wouldn't the increase from 50Hz to 60Hz also increase the impedance and thus limit the current to allow this American application to marginally operate?
@MTW The line-voltage controls are Klockner Moeller. Eaton has very close replacements that aren't too hard to cross-reference. I had to replace the main contactor in this machine about a year ago.
@MTW The line-voltage controls are Klockner Moeller. Eaton has very close replacements that aren't too hard to cross-reference. I had to replace the main contactor in this machine about a year ago.
Attachments
If increasing the frequency is accompanied by a proportional increase in voltage, the V/Hz ratio remains the same which is essentially “electrically neutral” for the motor. But the speed also increases which can cause problems depending on the characteristics of the load.
It’s not possible to answer you’re question definitively without knowing the characteristics of the load.
ptonsparky
Tom
- Occupation
- EC - retired
I had to read up on it again. FWIU, a 50 Hz will have less torque at start when run on 60.
So does the Wye start help with this?
So does the Wye start help with this?
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Torque is related to that V/Hz ratio. If you maintain that ratio within the +-10% tolerance, you get rated torque.
So in a 380V 50Hz motor, the V/Hz ratio is 7.6:1
In a 460V 60Hz motor, the V/Hz ratio is ... 7.67:1!
It's not coincidental. You can take a 380V 50Hz motor designed for the EU and use it here, no problem, and vice versa. They have technically gone to 400V 50Hz now, but still close enough.
The same isn't true at 240V though. An IEC 230V 50Hz motor has a V/Hz ration of 4.6:1, whereas our 240V 60Hz is 4:1, so more than -10%. The IEC motor would have less torque here. Whether that is significant or not would depend on the actual load on the motor. If the motor is a centrifugal pump designed around the 50Hz speeds, it will on the one hand run 20% faster here, so the HP requirement increases by the CUBE of that speed difference, meaning it needs 173% HP to operate. At the SAME TIME, the motor is actually producing LESS torque. It will overload fairly quickly. But if you take a NEMA designed motor and pump system from here and send it to a 50Hz country, the pump will require LESS HP at the slower speed, and the motor will be producing MORE than the original rated torque. The motor may run hotter from saturation, but with less actual load, it may be able to tolerate that forever.