27/04/2026
3S Technology Explained
Electric motors can suffer from poor, inefficient and noisy start/stop due to imbalances across the phases, although it is important to point out that minor phase imbalances always exist in the real world and electrical equipment or systems are designed to cope with these situations.
2-phase starters WITHOUT 3S technology incorporated in the firing method - a phase imbalance will create a dc component in the field which inflicts stresses in the form of locking torques creating vibration, heat and inefficient motor control. These stresses can mechanically damage internal components and result in noise being generated at start-up. Most small-power soft starters can only offer short starting times, limiting the number of applications they are useful for. Further difficulties can occur due to higher Locked Rotor Currents and power factor variances, compounding synchronization & firing issues in motor control. Loss of control of the load pulsing allows wobbling and notching of the torque forwards and backwards, generating high current levels causing overcurrent protection devices to operate.
3S Technology - a specifically formulated algorithm developed exclusively by Motortronics UK
implements an automatic ramp control sequence profile
ensures a smooth start/stop performance is delivered every time
without causing any undue stresses on the motor
noise level as per normal efficient motor start-up experiences
This unique algorithm;
enables stable acceleration & deceleration in all operating conditions
controllers adopt an asymmetric firing technique
delivering a per phase symmetry for motor loads
eliminates dc components inflicting stresses (torque vibration & heat)
constantly monitors signals from the motor
adjusts the firing delay angle in increments of 0.5µs
ensuring smooth starting and stopping performance
These techniques allow a longer start/stop time of 30 seconds
Myth - 4xSCR controlled soft starters have one of the phases uncontrolled, as you can see from the diagram (above right) this is not correct.
Motortronics offer two model ranges which incorporate 3S Technology - VMX-agility and VMX-PFE. Designed and manufactured in the UK, these soft starters not only allow smooth and effortless starting of 3-phase induction motors but can also be set-up to start single-phase motors.
