A 55 kW irrigation pump needs reduced-voltage starting to protect the motor and the piping from mechanical shock, but local electrical codes often require that the silicon-controlled rectifiers (SCRs) be bypassed after the motor reaches full speed. Selecting the wrong bypass contactor—or omitting it entirely—causes the SCRs to overheat and fail prematurely. The EM-GC and EM-GS series approach this differently, and the choice between them depends on how much integration you want in a single package.
The EM-GC is the standard series, designed for use with an externally supplied bypass contactor. The EM-GS builds the bypass contactor directly into the unit, which simplifies panel wiring and saves cabinet space. Both provide soft start and soft stop with current limiting from 200 to 500 percent of full-load amps, but the EM-GS adds pump-specific features like an anti-clog cleaning cycle and dry-run underload protection.
| Feature | EM-GC Series | EM-GS Series |
|---|---|---|
| Bypass contactor | External (user supplied) | Built-in |
| Soft start / soft stop | Yes | Yes |
| Current limit range | 200–500 % FLA | 200–500 % FLA |
| Pump cleaning cycle | No | Yes (anti-clog algorithm) |
| Underload protection | No | Yes (dry-run detection) |
| Modbus RTU | Optional | Standard |
If you're using the EM-GC with an external bypass contactor, sizing the contactor correctly is essential. For a 55 kW motor drawing 100 full-load amps at 415 V, the bypass contactor should be rated at 150 A minimum (AC-1 rating). A 75 kW motor at 135 FLA needs a 200 A contactor, and 110 kW at 195 FLA requires 300 A. Undersizing by even one category leads to contact welding and unplanned downtime.
The EM-GS eliminates these sizing decisions for most applications by including a contactor rated at 100 percent of the unit's full-load current rating. It automatically engages the bypass once the motor reaches full speed and disengages during the stop command. This reduces panel heat generation since the SCRs are shorted out after starting, and it eliminates the control wiring between the starter and an external contactor.
For pump and fan applications up to 110 kW, the EM-GS series with built-in bypass offers the simplest installation and the most features at a competitive price point. For fixed-speed applications where the bypass contactor is already panel-mounted separately, the EM-GC series provides reliable reduced-voltage starting at the lowest equipment cost. Both series work with Coolmay HMI monitoring systems over Modbus RTU.
Request a quote for EM-GC or EM-GS soft starters with matched bypass contactors. Download the selection spreadsheet to calculate starting parameters for your motor.
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