Bridgeport Boss 5 VFD / Power Question

[ken101ken101]

I am in the process of converting a Bridgeport Series1 Boss 5 mill to PC based using a VFD to control the spindle. For now I am going to run the original stepper motors and drives.
I have 220V single phase in the shop.

The main transformer T2 powering the drives has specs:
3 Phase Transformer 60hz
Primary: 230/460V 10/5A
Secondary 60-70-80V

What is the best way to power the drives with single phase 220v? Do I need a dedicated rotary phase converter to power the T2 transformer?

Any help or direction would be appreciated!

Thanks,
Ken

[Al_The_Man]

What is the nature of the 3 ph drive supply secondary? does a 3ph bridge feed a DC capacitor bank?
If so you could easily convert to 1ph transformer, ~2kva.
Al.

[ken101ken101]

Thanks Al,

I think so but I am not sure, you may be better to answer that than I. The schematic for my exact system (my T2 transformer is wired for 230v) is posted at
Bridgeport BOSS 6 transformer

The capacitors shown in the above schematic, C4,C1,C5 and C8 are all 5500MFD, 200VDC.

If it would help I can scan my schematic in full and post it or supply additional info, just let me know.
Thanks again,
Ken

[ken101ken101]

Does anyone have any suggestions on rewiring the 3 phase transformer to single phase? Or if I knew the original output of the transformer I believe through trial and error I could likely get close by moving the coil taps around.
The schematic mentions 56V for the end value of the power supply. Could I disconnect the drives and play with the transformer voltage until I see 56V?

My goal is to get this running using the original steppers and drives. The next step would be going to Gecko drives while keeping the original steppers. Even at that point it seems the original power supply is so heavily built it would be a shame to throw it away. Is this true or should I ditch it now and go with a toroidal transformer and power supply based on Bob Cambell's site?

thanks,
Ken

[Al_The_Man]

You could try and power up the two outer sections with 240 1ph and see what you get on the output, treat it as two separate transformers, the current may be somewhat higher.
Leave the centre section unconnected.
Al.

[ken101ken101]

I'm not having a lot of luck with getting the single phase to work. The voltages on the x, y and z are all over the place relative to each other.
I've decided to go ahead with a new power supply and Gecko drives. It seems the most common power supply voltage is 70V but I've read posts where people are running between 50v and 80v. Whats the advantage of 80v over say 50? If the Gecko drives are rated for 8A and 80V does it make sense just to go with 80V?

I'm looking at an Antek power supply with the following specs:
Power 1500W
Output Voltage Current
70V 21.4A
24V 2A
5V 1A

Any opinions would be appreciated.
Thanks,
Ken

[Al_The_Man]

The higher voltage would allow operating up to the max motor rpm.
The normal HV rating in order to get max motor rpm is for the PS voltage to be at least 10% higher than the motor rated voltage, anything lower and the max rpm will be affected.
Al.

[ken101ken101]

Is going more than 10% over the motor voltage potentially harmful or just not yield any benefit?

Thanks,
Ken

[Al_The_Man]

Is going more than 10% over the motor voltage potentially harmful or just not yield any benefit?
Ken

No harm, see Power-Supply Considerations For Servo Amplifiers
Al.