[oxford]

Before I get to the meat of my question, I need to verify that inverters and VFDs are synonymous.

So I took a gamble and bought a pair of spindles second hand on ebay for cheap. I have never used anything but a router before so I was hoping to break into spindles and not loose much if something goes wrong.

Now I need to figure out how to get a way of running the spindle.

How do I match inverters to their spindles? 400V, 13A and the other 400V 1.3A.

Can the spindles be run at a lower voltage? Does the frequency a spindle is run at control the speed, and the voltage the torque?

Do I need measure the inductance of the spindle for matching an inverter to it?

I asked the company for info, but as these are second hand, I won't be holding my breath for much.

Thanks in advance for the advice.

[Al_The_Man]

VFD's are often referred to as inverters.
Yes the frequency does control rpm and to a great extent, voltage the torque.
You may be out of luck running them on lower voltage.
The matching is usually to the current at base speed of the motor and HP.
400v is an odd voltage? Usually 440/480?
Al.

[Zig]

Like Al said, frequency will alter speed of rotation and voltage will alter torque ( and subsequently current) .

It is this "subsequent " aspect of VFD that needs to be understood.

A spindle in genral is a squirel cage motor with amazing dynamic balance and bearings which allow the motor to run up to very high speeds ( tens of thousands of RPM.

A sad fact of life however is that as the drive frequency goes up at a constant voltage the motor current tends to drop off inversely with frequency.

In fact it is not the voltage but the current which control the motor torque ( power ).


So in order to obtain a reasonable performance from the squirel cage motor as frequency changes so must the voltage.

Often the frequency voltage curve of the VFD is programmable to match the motor characteristics.

If You know the Voltage frequency ratio for the motor You ought to be able to workout min and max voltage at min and max frequency and establish whether a VFD will drive the spindle happily at the motor power rating.

[oxford]

Yes, there is 400V engraved on the side of the spindle...Still crossing fingers MIESYSTEMS will get back to me.

I have been looking at VFDs and see specs like "0-400Hz" and 16k carrier frequency.

Is the 0-400Hz the output to motor frequency?

Does the carrier frequency have to do with the frequency for which a pwm signal from the computer has to match in order to communicate with the inverter?

Thanks

[Zig]

0-400 Hz is the output frequency ( well not quite zero .. AC motors dont run on DC ) .

If the motor is wound as a single pole pair then at 60Hz it will want to run at 60RPS= 3600RPM

I said tend to. Actual speed will depend on the motor load since the AC induction motor needs to run at some so called SLIP FREQUENCY in order to generate the required torque.

As for carrier frequency.. thinkof it a base beat from which other frequencies are synthesised.
The higher the base beat the smaller the incrementswith which other frequencies can be synthesised.

The implication of this is smoother speed control.

[oxford]

Thank you. That really helps.

Do I need to make any measurements of the inductance or resistance of the motor windings?

Since the voltage is rated over 120V, would I burn out the motor just hooking it up to a 120v outlet for kicks and giggles?

Appreciations,

[Al_The_Man]

I am assuming these are 400v 3 phase spindles, and apart from the voltage issue, it will not achieve anything trying to hook them up to 120v 1 phase, if this is what you mean?
1 ph motor and 3 ph motor are two different animals.
Al.

[oxford]

There are six leads to the spindle

[Al_The_Man]

Sounds like 3 phase dual voltage?
Al.

[oxford]

I took out my ohm meter and tried out all the six leads.

Three of the six are connected to each other.

After this test, MEI got back to me and told me that the spindle was 3-phase 400v 5-36k rpm, water cooled with ATC. Unfortunately, I was also told that the tool holder is not standard and not available on the market.

The guy asked for the serial number and where I got it from....Can hardly wait to find out what's next from here.

[Al_The_Man]

I took out my ohm meter and tried out all the six leads.

Three of the six are connected to each other.

After this test, MEI got back to me and told me that the spindle was 3-phase 400v 5-36k rpm, water cooled with ATC.

It sounds like it may be star connected windings.
If this is a 2 pole motor, then you will need a VFD to output 600hz to achieve 36k rpm.
Al.

[oxford]

Any good link I can look up different AC motors at?

Thanks

[oxford]

I found some transformers to step down 400v to 115.

Can I run it backwards to step up 115 to 400V?

Since this would be one phase, Could I use it to power a 3HP drive to run the 1.5HP motor?...or do I have to worry about some weird power line reactions doing this?

Thanks

[oxford]

Can any VFD be derated?...I think that is the word when I use a higher HP drive, but with one phase instead of three phase power source to run the drive.

[Al_The_Man]

Some VFD's are derated when used on single phase supply, depends on the manufacturer.
As far as the motor details, it can usually be programmed in to the parameters.
Al.

[oxford]

Thanks.

Will a manufacture state in their manual if the VFD can be derated, or is this something you just have to do and see what happens?

[Al_The_Man]

If you are lucky, they publish it in the manual.
Al.