Solid state soft starter Type VFS

Reduced voltage soft starter (RVSS)
Rated voltage: up to 17,5 kV
Rated current: up to 1400 A

Product Information
Rated voltage:
Rated current:
up to 17,5 kV
up to 1400 A

Solid state soft starter type VFS

The solid state soft starter type VFS from Mocotech GmbH is a microprocessor controlled reduced voltage soft starter (RVSS) for medium voltage three phase induction asynchronous and synchronous motors.

The advanced controller technology with integrated motor protection functions increase your process stability and protects your equipment. Different selectable and adjustable starting characteristics reduce the voltage drop in your power supply and eliminate reliable the mechanical stress on your equipment during motor acceleration. For some applications like water pumps it might be beneficial to slowly decrease the speed of the motor instead of coasting to a stop. The solid state soft starter type VFS provides a soft stop function with final torque adjustment for these applications.

We start your large drive and with the integrated motor protection functions our solid state soft starter type VFS protects your motor against electrical, mechanical and thermal stress during start-up, soft stop and continuous operation.

Never accept less than the highest standards!

The solid state soft starter type VFS is type approved according to IEC 62271-200 and will be manufactured in compliance with IEC standards, the EC directives and the ISO 9001 standard. Individual approvals by ABS, BV, DNV-GL, LRS, etc. are available for our solid state soft starter type VFS.

Do not waste time during installation and commissioning!
Each solid state soft starter type VFS will be delivered factory tested and completely assembled with a preset software as a turnkey solution.

Never fear to lose the control about your process!
Your operators have the direct access to all functions, the settings and the status of our solid state soft starter type VFS via the self-luminous alphanumeric plain text display with keypad and the serial interface.

Minimize expenses for maintenance and repairs!
The exclusive use of parts with a high reliability together with our TQM ensure a meantime between failures (MTBF) which meets highest expectations. The clean design grants easy access to all components and keeps the meantime to repair (MTTR) at a minimum.

Technical specification (other on request)

Technical specification
Rated voltage: 3,6 kV up to 17,5 kV
Operating voltage: 2,3 kV up to 13,8 kV
Power frequency withstand voltage: up to 38 kV
Basic impulse level (BIL): up to 95 kV
Peak inverse voltage (PIV): up to 41000 V
Rated frequency: 50/60 Hz
Rated current (FLC): up to 1400 A
Rated short circuit current: up to 40 kA
Rated short circuit duration: 1 s
Max. starting current of FLA: 400 % *
Max. starting and stopping time: 20 s *
Number of starts per hour: 3/2 *
Control voltage: 230 V AC *
Communications protocol: MODBUS RTU RS485 *
Ambient temperature: 0 to +50 °C *
Relative humidity: 5 to 95 %
Installation altitude: ≤1000 m *
Degree of protection:: IP 4X up to IP54
Cable entry: Bottom *
Cabinet colour: RAL 7035 *
*other on request

Protection functions

ANSI Code Description
19 Starting to running transition
27 Undervoltage
37 Undercurrent
37 Underpower (optional)
38 Bearing RTD protection (optional)
39 Mechanical condition protection (optional)
46 Phase-balance current
46 Phase loss
47 Phase-sequence
48 Incomplete sequence
48 Locked rotor
49 I²t electronic motor overload
49 Stator RTD protection (optional)
50 Instantaneous overcurrent
50G Instantaneous earth overcurrent
51 AC inverse time overcurrent
51G AC inverse time earth overcurrent
51LR AC inverse time overcurrent/locked rotor
55 Power factor protection (optional)
59 Overvoltage
66 Number of starts per hour
81 Frequency protection (optional)
86 Lockout
94/95 External fault
  Shorted thyristor (SCR) protection
  Thyristor (SCR) overtemperature protection
  Transient voltage protection (optional)


The solid state soft starter type VFS from Mocotech GmbH provides you with multiple options and extended functions for the motor acceleration and deceleration. A suitable acceleration and deceleration ramp is available for almost all applications and can be easily selected via the self-luminous alphanumeric plain text display with keypad and the serial interface.

Suitable ramps can be selected depending on the load requirements during starting and stopping. Special ramps beside the well-known and commonly used constant current ramp can be enabled to suit any individual application or network requirement. The selectable and adjustable pulse start (kick-start) function provides the motor with a torque boost for the breakaway of heavy loads. Furthermore, the dual adjustment feature provides multi-selectable parameters for two different motor settings or for perfect matching of any torque or current limitation requirement, such as extra-smooth ramping in generator-supplied networks. The soft stop function with adjustable final torque enables you to control the deceleration of your motor and load to avoid the water hammer on pump applications.