Quote:
Originally Posted by boltboy49
Got any better pictures of the motor tag? I sure would love to read the left edge. I think it is saying 1.5 amps at high voltage and 3.2 amps at low voltage. Making some assumptions I calculate the horsepower to be 1.5.
I would tend to lean in the vfd direction. Purely because of the gain of variable speed.
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Al, that is the only photo of his tag that I have. Here is my tag and perhaps it will help.
20210823_174949_compress93.jpg
Here is my friends tag for reference:
20210823_114756_compress87.jpg
Note that my machine is 60 hz.
Quote:
Originally Posted by BSG - KEVIN
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I think you’re putting too much voltage to the motor, it should be 380 volts not 480, common European voltage!
Also you need to check and see what the converter is suppling, 480 Delta or 480 Wye, Delta will have a high leg, the Wye will have three balanced legs?
The heaters need to be sized for the voltage used, you can replace the whole contactor with a new one if you can’t find heaters for the current starter?
Another option, pull the motor and have it rewound to single speed and the voltage you have available, this solves the problem if the motor is not a standard mount, then use a VFD.
One thing to keep in mind with two speed motors, with a VFD you can only use one speed, but the VFD makes up for that!
You didn’t mention if this is the only three phase machine, is there three phase at a lower voltage available, if so you could use a step up transformer?
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You raise some good points Kevin. I'm not near the machine and can't easily measure the voltage.
The issue is multi faceted.
1- High voltage 3 phase is not really desirable in my friends shop although it is available. Long story and not really relevant.
2- Current Contactor and heaters do not work correctly because of the 50 hz thing.
3- Low voltage 3 phase is wired THROUGHOUT the shop and the rotary phase converter runs nearly continually because there are many 3 phase machines (low voltage 3 phase)
So the goal is to get this machine on low voltage. Restrapping the motor is easy and I understand and have verified how to do that.
I can probably find a correct contactor and heater for the motor BUT, it will still be 50hz and run 20% fast. My KF460 is a 500V 50hz machine. I'm running it at 480V 60hz via a big Westinghouse transformer. It works fine but does run 20% faster than normal. It is a two speed motor and I don't use high speed anyway.
The best solution would be a 3phase to 3 phase VFD of sufficient size to run the motor ONCE IT IS CONVERTED TO LOW VOLTAGE 3 PHASE. We don't want to run it on single phase because there are 3 phase (low voltage) drops every 8 feet around the large shop.
So I'm looking for information on:
Option 1 - replacing the contactor/heater and restrapping to low voltage 3 phase
1- what the motor is in terms of HP and amp draw on low voltage?
2- what contactor and heater would it need and/or who can I talk to that can sell me the correct one?
Option 2 - restrapping the motor and going with a VFD
1- does this bypass the contactor. That is, does the VFD perform the same function as the contactor which is nothing more than a big relay with overload protection provided by the 'heater'
2- I THINK the VFD option will bypass all the original start stop controls on the machine. That's not a problem just different buttons to push.
3- what size VFD is needed? I don't know enough to talk intelligently to anyone and don't want to have my friend buy something and it not be the correct one.
4- I've done some internet searching on VFDs and only understand every 4th word.