How do you figure three phase amps. When all you know is the voltage and the wattage. Do not know the PF factor

For example, with the following values:

208 Volts 3 phase

15000 watts or 15 KVA

Assume .8 PF

VA (AC Watts)= E*I*PF*1.73

I= KVA/E*1.73*PF

Amps = 15000 watts divide by 208 volts times 1.73 times .8

Amps = 52.10 amps

If this is for resistance heat, no need for PF.