The equations for calculating the power requirement for VFD has been discussed in Selection of Variable Frequency Drives.
Using the equation below, we will provide some examples on selecting a VFD for a specific motor.
Note:These motors are used for electric submersible pumps hence the voltages are different from the usual motor ratings.
1. For the 150HP motor data:
ηvfd = 95%, VFD Efficiency
ηmotor = 85%, Motor Efficiency
Vmotor = = 2100 V, Motor terminal voltage
Imotor = 46.6 A, Motor current
PFmotor = 0.95, Motor power factor
2. For the 300HP motor data:
ηvfd = 95%, VFD Efficiency
ηmotor = 85%, Motor Efficiency
Vmotor = = 2940 V, Motor terminal voltage
Imotor = 78.9 A, Motor current
PFmotor = 0.95, Motor power factor
Selection of VFD
1. Based on Toshiba VFD catalogue:
The VFD ratings for each of the motors above will be:
1. For 150 HP Motor - Toshiba T300MV2, Model 400 HP, 50A, 4160V.
2. For 300 HP Motor - Toshiba T300MV2, Model 700 HP, 87A, 4160V.
2. Based on ABB VFD catalogue:
The VFD ratings for each of the motors above will be:
1. For 150 HP Motor - ABB ACS1000-033-A01A-J4-010, 70A, 3300V.
2. For 300 HP Motor - ABB ACS1000-033-A01C-J4-010, 87A, 3300V.
3. Based on WEG VFD catalogue:
The VFD ratings for each of the motors above will be:
1. For 150 HP Motor - WEG Model MVW01-C096-T3300-EH30G2Z, 85A, 3300V.
2. For 300 HP Motor - WEG Model MVW01-C096-T3300-EH30G2Z, 85A, 3300V.
Final Note
The size selection of a variable frequency drive (VFD) should be based on motor voltage and current and not on the torque or power rating.