Challenge
A plunger pump is a reciprocating load: its large medium-voltage motor must overcome high liquid pressure at standstill, demanding substantial starting torque. Direct-on-line starting of such a motor draws high inrush current, causing voltage dips on the site bus and mechanical stress on the pump drive train. On a petrochemical or oilfield site — often remote, outdoor and partly in hazardous areas — the starting equipment must be reliable, simple to operate and monitor remotely.
For plunger pump applications, an initial voltage of around 40% is a common field setting used to limit the starting current while still delivering enough torque to move the pump. The site’s target in this case was a current limit of 300% Ie with a 15 s start ramp.
Solution
Supplied a CMV series medium voltage soft starter for the plunger pump drive. The CMV series ramps the motor voltage through SCR thyristor firing with CFT optical-fiber trigger isolation, cutting inrush current while delivering enough torque for the reciprocating load. A built-in vacuum bypass contactor with redundant direct-start function keeps the pump running even in the event of a valve-group fault.
Site parameters were set as: initial voltage 40%, current limit 300% Ie, start time 15 s. Communication via Modbus RTU/TCP over RS485 allows the starter to be monitored from a remote control room or SCADA system — important for unmanned oilfield and petrochemical sites.
Results
- Xichi CMV series medium voltage soft starter configured for a plunger pump application in the petrochemical industry
- Site parameters set: 40% initial voltage, 300% Ie current limit, 15 s start time
- SCR-based voltage ramping limits inrush current and reduces mechanical stress on reciprocating pump starts, while the built-in bypass takes over at full speed
FAQ
Why does a plunger pump need a medium voltage soft starter?
A plunger pump is a reciprocating load that demands high starting torque from its motor. Direct-on-line starting draws high inrush current, causing voltage dips and mechanical stress. A medium voltage soft starter ramps the motor voltage through SCR control, limiting inrush current while delivering enough torque to accelerate the pump smoothly.
What do the site parameters — 40% initial voltage, 300% Ie current limit, 15 s start — mean?
Initial voltage is the voltage applied at the moment of starting (here 40% of rated). Ie is the motor rated current, so a 300% Ie current limit caps the starting current at 3 times rated. The 15 s ramp brings the motor from 40% up to full voltage over 15 seconds, giving a controlled, low-stress acceleration.
Can a soft starter provide the torque a reciprocating plunger pump needs?
Yes. The starting parameters are set to match the pump duty: a low initial voltage limits current, while a suitable ramp and current limit keep enough torque to overcome the pump’s standstill resistance. Confirm your pump’s torque curve and we will set the parameters accordingly.
Is the CMV series suitable for outdoor oilfield or hazardous petrochemical environments?
The CMV series is an IP40 indoor cabinet design with an explosion-proof version available for hazardous areas. For outdoor oilfield installations, confirm the required enclosure protection and zone classification with our engineers and we will match the correct cabinet configuration.
Soft starter or VFD for a plunger pump?
If the pump runs at fixed speed and only needs smooth starting, a soft starter is the lower-cost, lower-complexity solution. A VFD adds continuous speed control, but for medium-voltage motors it is significantly more expensive. For applications where variable flow control is required, see our medium voltage VFD.
How is the starter monitored at a remote oilfield or petrochemical site?
The CMV series supports Modbus RTU and Modbus TCP over RS485, with up to 31 units networked on one bus. Operators can read running status and motor parameters and perform remote start/stop control from a SCADA or DCS system — designed for unmanned sites.
