Hello Everyone
I have a problem with determining motor speed driven open loop from a VFD.
Motor Data: 100 hp 480V 3 phase, 109A FLA 1780RPM
This motor is running a fan that can not exceed 2000RPM. It is currently pulling around 80amps so I know we are not exceeding the Hp of the motor.
The VFD is set at 66Hz
So I know assuming the 1780 is a good number that the motor is running at 1958RPM. My question is two fold
1. Is using full rated load RPM to calculate speed a good practice at loads well below rated load?
2. I followed the threads explaining that using motor current draw to calculate Hp is not a good idea. My AB Power Flex drive displays Flux amps and another amp variable. I am assuming the variable who’s name escapes me right now is the current in phase and therefore a good current number to calculate real work being done by the motor.
Flux amps were 38amps
the other amp variable was 64amps
Does this mean I can ignore motor eff and power factor to get real Hp ratings using in phase current draw?
( E * I * 1.73 )/ 746
I have to get this right. If that fan explodes…they will use my body as replacement fan blades....I run with a rough crowd
Steve D
I have a problem with determining motor speed driven open loop from a VFD.
Motor Data: 100 hp 480V 3 phase, 109A FLA 1780RPM
This motor is running a fan that can not exceed 2000RPM. It is currently pulling around 80amps so I know we are not exceeding the Hp of the motor.
The VFD is set at 66Hz
So I know assuming the 1780 is a good number that the motor is running at 1958RPM. My question is two fold
1. Is using full rated load RPM to calculate speed a good practice at loads well below rated load?
2. I followed the threads explaining that using motor current draw to calculate Hp is not a good idea. My AB Power Flex drive displays Flux amps and another amp variable. I am assuming the variable who’s name escapes me right now is the current in phase and therefore a good current number to calculate real work being done by the motor.
Flux amps were 38amps
the other amp variable was 64amps
Does this mean I can ignore motor eff and power factor to get real Hp ratings using in phase current draw?
( E * I * 1.73 )/ 746
I have to get this right. If that fan explodes…they will use my body as replacement fan blades....I run with a rough crowd
Steve D