How to size buck/boost xfmrs?

[ssandoval]

We have moved into a new M&O facility at my school district; the carpenter shop foreman has an oldie-but-goodie Delta tablesaw that was connected via single-phase 240v/ 20amp circuit. The 240v panel was VE'd out at our new shop and only has 208-120v service for the shop areas. How do I size a boosting transformer to meet this need? I'm sure this is a very basic issue but I have never had to install one.

 

[stickboy1375]

We have moved into a new M&O facility at my school district; the carpenter shop foreman has an oldie-but-goodie Delta tablesaw that was connected via single-phase 240v/ 20amp circuit. The 240v panel was VE'd out at our new shop and only has 208-120v service for the shop areas. How do I size a boosting transformer to meet this need? I'm sure this is a very basic issue but I have never had to install one.

I generally just call the manufacture of the buck/boost company.


I'm not worthy..

 

[ronaldrc]

Take the voltage difference between your supply voltage and what you want to change the voltage to, and use this voltage to determine the Kw of the transformer.

240-208=32 volts 32 volts x 20 amps.=640 watts or a 640 Va, I would go with a 1 KW.


You can do this because the low voltage winding of the 32 volts is heavier wire.


If this is not right please correct me.

 

[LarryFine]

You can do this because the low voltage winding of the 32 volts is heavier wire.

If this is not right please correct me.

It sounds right. The primary is excitation current, and doesn't count (beyond the source having to supply it, of course.)

The secondary has to provide the load's current, but only at its voltage, so it doesn't have to match the load's VA.

 

[rt66electric]

Buck boost not needed

Buck boost not needed

Hello ..


Im new to this forum. Please excuse me if I type badly. IN responce to the Buck/boost question .. I have general found that any general 240 motor will run on 208v. The only time I have had problems is on computer and control syatems, changing the taps on the control XFMER usually cures problems.. If that Heavy_DUTY saw is as solid as i think is ,and has a manual motor starter,and as little as it would be used in a school enviroment, plug er in and run it. If you look at the HP charts the 208v motors draw alittle more amps than the 240's .. THey will run the same speed but will have a little less power or draw more amps than the name plate. From experience a motor will run fine from 190v to 260v : howerver the coils on the control relays will "chatter" on undervoltage and release "magic smoke" on overvoltage.. DEnnis

 

[Besoeker]

We have moved into a new M&O facility at my school district; the carpenter shop foreman has an oldie-but-goodie Delta tablesaw that was connected via single-phase 240v/ 20amp circuit. The 240v panel was VE'd out at our new shop and only has 208-120v service for the shop areas. How do I size a boosting transformer to meet this need? I'm sure this is a very basic issue but I have never had to install one.

Check the current on the table saw nameplate.
Multiply that by its rated voltage. That will give you minimum required VA rating. To get it in kVA, divide by 1000. Above all, do not confuse kVA with kW.