Section 3– Page 6
The following formula can be used for transformer sizing. For each secondary winding,
the power in VA is:
Ps - (Paz * 1.5) * 1.73 /
√
(n+2)
where:
Paz = (Vm1*Cm1 + Vm2* Cm2 + ............ +
Vmn*Cmn)
Vm = motor max speed in rad/sec (RPM/9.55)
Cm = nominal motor torque in Nm(lb-in/8.85)
1.73/
√
(n+2) = corrective factor when using more than one
drive supplied in parallel with n= number of drives.
The overall transformer power in VA is:
Pt = Ps1 + Ps2 ............ + Psn
where:
Ps1 = power of secondary winding 1
Ps2 = power of secondary winding 2
Psn = power of secondary winding n
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