A 37 kW pump needs to start smoothly, but does it need a variable frequency drive or would a soft starter be sufficient? Engineers routinely overspend on VFDs for applications that only need reduced-voltage starting, or they use a direct-online contactor and deal with mechanical shock, pipe hammer, and voltage sags. The EM-GU online soft starter fills the gap between a contactor and a full-featured VFD, and understanding where each solution fits saves both money and maintenance headaches.
The deciding factors come down to what you actually need the motor to do after it starts:
| Requirement | DOL Contactor | EM-GU Soft Starter | VFD (EM10) |
|---|---|---|---|
| Cost (37 kW class) | Lowest | Low to medium | High |
| Starting current | 600–800 % FLA | 300–400 % FLA | 100–150 % FLA |
| Speed control | No | No | Yes (0–400 Hz) |
| Torque control | No | Limited (kick-start) | Full (torque vector) |
| Mechanical shock | Severe | Low | Minimal |
The EM-GU soft starter is the right choice when the motor runs at full speed after starting and your only goal is reduced mechanical shock. Pumps, fans, and compressors fit this profile perfectly. The EM-GU is smaller than an equivalent VFD, costs less, and generates less heat in the panel because the SCRs are bypassed after start. For applications requiring variable speed—flow control, precise torque positioning, or controlled deceleration—a VFD is non-negotiable.
For 15 to 75 kW pump and fan applications running at nominal speed after startup, the EM-GU series soft starter provides the ideal cost-to-performance ratio. If variable flow or speed control becomes necessary, the EMHeater EM10 series VFD handles those requirements seamlessly. Both solutions integrate with Coolmay HMI/PLC monitoring over Modbus RTU, so switching between platforms doesn't require a control system overhaul.
Request a quote for EM-GU soft starters. Download the comparison chart with installation dimensions and wiring diagrams for both solutions.
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