# Some questions about a servo motor driver input ratings

A servomotor drive input can be supplied either 3-phase or single phase. The photo of the driver nameplate is shown as follows:

Does that mean in full/nominal load if this drive is supplied single-phase, it will draw 9.9 Ampere rms current through line? This makes sense to me because I=P/V so I = 2.38KVA/240 is around 9.9A. I might have ignored power factor(?)

But FL current is written as 9.9/4.6 A. Does that mean in case of three-phase power input the total current drawn will be 4.6 A. How can we calculate 4.6 Ampere from 2.38KVA?

motor nameplate:

• Power of three phase is $P=\sqrt{3}\cdot V\cdot I$ – Marko Buršič Mar 15 at 11:59
• But in that case I calculate the current I = P/(sqrt(3)*V) = 5.72 A in nameplate it says 4.6 A (?) – cm64 Mar 15 at 12:17
• Well, also the output power 240V @ 6A would give 2.5kW which is higher than input power. You'd better ask the manufacturer what is the meaing of the data. – Marko Buršič Mar 15 at 12:28
• You probably need to find a more detailed specification in the instruction manual or other publication. Nameplate information tends to be based on worst case or conditions set by safety standards. That sometimes leads to inconsistencies. The 2.38 kVA may be the short-term maximum under worst case conditions while the full-load current is continuous current under typical conditions. – Charles Cowie Mar 15 at 12:29
• The output kVA can be higher than the input kVA because there is inherent power factor compensation in the controller. – Charles Cowie Mar 15 at 12:31

Now look carefully. Continous output power @ rated input current: It says for 3x240VAC input voltage, that will have 4.6A rated input current, the output power is 1250W.

Let's calculate the output voltage: $$\V=\dfrac{1250VA}{\sqrt{3}\cdot 6A}= 120V\$$

It makes sense now, te input apparent power is 2kVA and the output power is 1.3kVA. But this driver can't provide output voltage 240VAC @ 6A. You'd need to contact the manufacturer for further explanations.

Anyway, what is the connected motor?

I'll explain later...

• Here is the motor's nameplate i.stack.imgur.com/WvvAh.jpg – cm64 Mar 15 at 13:57
• Hello again, how did it go with the answer, you were elaborating. thanks – cm64 Mar 18 at 9:44
• @cmd The manuals and datasheets have typos. Your drive can supply 2000W output, not 1250VA as declared in first datasheet. The motor will suit very good, you can install fuses according to the manual. What really concerns you? I can edit the answer with choosen motor - output voltage, output current on S1 duty. – Marko Buršič Mar 18 at 10:31