PUMP · SOFT START
75kW / 100HP pump: reduce current shock and water hammer.
This example shows the engineering path. It is not a universal bill of materials: the final model follows the motor nameplate, supply system and starting duty.
Why voltage changes the answer
| Application reference | Catalog starting point | Current risk | Engineering decision |
|---|---|---|---|
| 75 kW at AC380 V | NJR5-150/ZX3 · 140 A · catalog 75 kW | Confirm actual nameplate FLA and starting duty | Use catalog model only after current and duty check |
| 75 kW at AC460 V | NJR5-110/ZX4 · 103 A · catalog 75 kW | Actual motor FLA may exceed 103 A | Move to the next frame when nameplate current or duty requires it |
| 100 hp at 460/480 V North America | Compare 103 A and 140 A frames | 100 hp motor current may be above the smaller frame | Select by nameplate FLA, code requirements and starting duty—not kW conversion alone |
The important difference: 75 kW and 100 hp are close in mechanical power, but the motor design and nameplate current can make the required soft-starter frame different.
System-level checks
01 · MOTORVoltage, FLA, frequency and service factor
02 · LOADPump inertia, valve condition and required ramp
03 · DUTYStarts per hour, start time, ambient and altitude
04 · COORDINATIONProtection, bypass contactor, control voltage and enclosure
What to send for a model-level answer
- A clear motor-nameplate photo
- Supply voltage and control voltage
- Pump type, operating head and known water-hammer problem
- Starts per hour and approximate acceleration time
- Existing breaker, contactor and control-panel information