bmw318be
Mechanical
- Jun 16, 2010
- 197
Hi,
We have triplex pump running for sometime with VFD of 20% of 50 HZ
Cat Pump
11 KW 4 Pole motor 400 V
Maximum current 415 V is 20.2 Ampere.
We see the running current at Discharge Pressure of 51 Bar is 20.6 Ampere and at 0 Bar is 11 Ampere.
At 0 Bar to 45 Bar, the motor was running okay, no trip. Until it reaches 20.6 Ampere of 51 Bar it tripz.
some doubts to clarify
1. We find the plungsr is tight if hand rotate by shaft when motor was coupled.
2. At 51 Bar, it is trip after 15 minutes of running due to Motor ovwrload.
3. From the Cat website, this formula is the motor sizing
HP= flow in GPM x PSI / 1450
The model ia 1541
Max Flow 19.3 gpm / 73 lpm
Max Pressure 1200 PSI
RPM 1180
Is recalculating the power at VFD speed would be as followed.
10 PSI case of 20% speed
HP= ( 0.2 of 19.3) x 10 PSI / 290 RPM = 0.134 HP
We found that it did not correspond to running current which show 11 Amperes which used up around 50 % of motor rated current of 20.3 Ampere at pressure.
If we used the running current of the pump at 10 PSi.
Converting to power = 400 V x 11 =4400 Watt or 0.44 KW or 0.54 HP. This seemed fsr off from the manufacturer calculated formula when run ay 20% of speed.
4. What could be the cause of overload, is there a way to calculate the real running current using VFD theory at 20% OF 50HZ.
5. Any experience the piston pump has mechanical failure and caused pump shaft to stiffly rotated so the running current is higher.
We have triplex pump running for sometime with VFD of 20% of 50 HZ
Cat Pump
11 KW 4 Pole motor 400 V
Maximum current 415 V is 20.2 Ampere.
We see the running current at Discharge Pressure of 51 Bar is 20.6 Ampere and at 0 Bar is 11 Ampere.
At 0 Bar to 45 Bar, the motor was running okay, no trip. Until it reaches 20.6 Ampere of 51 Bar it tripz.
some doubts to clarify
1. We find the plungsr is tight if hand rotate by shaft when motor was coupled.
2. At 51 Bar, it is trip after 15 minutes of running due to Motor ovwrload.
3. From the Cat website, this formula is the motor sizing
HP= flow in GPM x PSI / 1450
The model ia 1541
Max Flow 19.3 gpm / 73 lpm
Max Pressure 1200 PSI
RPM 1180
Is recalculating the power at VFD speed would be as followed.
10 PSI case of 20% speed
HP= ( 0.2 of 19.3) x 10 PSI / 290 RPM = 0.134 HP
We found that it did not correspond to running current which show 11 Amperes which used up around 50 % of motor rated current of 20.3 Ampere at pressure.
If we used the running current of the pump at 10 PSi.
Converting to power = 400 V x 11 =4400 Watt or 0.44 KW or 0.54 HP. This seemed fsr off from the manufacturer calculated formula when run ay 20% of speed.
4. What could be the cause of overload, is there a way to calculate the real running current using VFD theory at 20% OF 50HZ.
5. Any experience the piston pump has mechanical failure and caused pump shaft to stiffly rotated so the running current is higher.