I need to buy a power supply that have AC output (because my drivers requiered 80 ~ 220 VAC) but I need to know my motor power rating.
here is my motor spec:
2 phase bipolar
4.2 VDC
6.5 A/phase
resistance 0.65 Ohm/phase
Inductance 26 mH/phase

2. ...and what is your mains supply voltage?

3. my stepper driver main supply can accept 80 ~ 220 VAC

4. You don't need a power supply! If your mains voltage is outside the 80-220V range, then you need a transformer to step the voltage (presumably down) to that range.

Your motor uses 27.5 Watts (Power=Voltage * Current) per phase, but the controller will need considerably more. It's always best to have a large safety factor: if there is only a single driver and a single motor, then I'd consider a 100W transformer minimum. If there are more drivers and/or motors, then multiply accordingly.

• I definitely need a transformer because here the source is 220 VAC and the driver max can handle is 220 VAC and I thought I could use Mariss formula which is square root of 26 * 32 = 163.16 Volt to supply the driver but I don't know how much amps to go with that 163.16 volt.

• You obviously don't understand my question. This implies a severe lack of knowledge about electricity, particulary mains electricity, you should find an expert and let him help you before you join the Darwin awards.....
You can't know everything, so don't get upset.....
DKWarner is right too.

• Hi

Are you sure you need a transformer ?
From your data, seems that the driver has a universal input (typically 110 to 240V +/-10%).

regards

• The maximum Supply voltage is up to220VAC
 Output current up to 7.8A(5.57 ARMS)

Parameters 22078
Min Typical Max Unit
Output current 0.42 (0.3A RMS) - 7.8 A
Supply voltage 80 180 220 VAC
Logic signal current 7 10 16 mA
Pulse input frequency 0 - 400 Khz
Isolation resistance 500 MΩ

see the attachment for details on the stepper driver
as you can see that the maximum allowable supply voltage is 220 VAC and in my country the main voltage is 220VAC but can be plus or minus 15% so when my main voltage higher than 220VAC I will fry my driver for sure that's one of the reason I need a step down transformer but on the other hand you can see the motor rating is most suitable when I supply it with 163 VAC according to Mariss formula. But My question how much amps or watt I will be needing at 163 VAC.

here is my motor spec:
2 phase bipolar
4.2 VDC
6.5 A/phase
resistance 0.65 Ohm/phase
Inductance 26 mH/phase

• What you need is ac voltage regulation. There are several manufacturers of these devices. APC is one of the best.

http://tinyurl.com/acv-regulation

• No I don't want to feed it 220Vac but I want to feed my stepper driver 163 VAC and my question is how many watt or amps do I need for each stepper drivers if I were to give it 163 VAC?

• Just use an isolating transforma that goes from 230V to 110V AC.
If you put 230V into this driver the motor will fry, and any AC spikes will pop the driver.
Even at 110V the motor will still get quite hot, so really the AC voltage needs to be defined by your application, and how fast you need the motor to go.

you can also feed in DC to the driver, because all the driver does in rectify the AC, so 220V AC would be over 300V DC onto the driver.
If you can get 60V AC, that would be better.

Also i would look at a 1.5KVA for three axis or 500VA for one axis.

Originally Posted by 15mgtar
No I don't want to feed it 220Vac but I want to feed my stepper driver 163 VAC and my question is how many watt or amps do I need for each stepper drivers if I were to give it 163 VAC?

• How about a buck / boost transformer ,( step up/ step down) one with a 24 / 48 secondary would knock 48 volts off the mains voltage. 1KVA would be more than enough for your motors. not sure if the Marris formula directly relates to this drive since it is a DC formula and your working with AC.

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