Medium Voltage Soft Starter 3kV / 6kV / 10kV for 400-12,500 kW Motors – CMV Series

Medium Voltage Soft Starter 3kV / 6kV / 10kV for 400-12,500 kW Motors – CMV Series

The CMV series is a solid-state medium voltage soft starter for 3 kV, 6 kV and 10 kV squirrel-cage asynchronous and synchronous motors from 400 kW to 12,500 kW. It uses SCR thyristor firing with optical-fiber trigger isolation to ramp the motor voltage during starting, cutting inrush current, reducing impact on the grid, the motor and driven machinery, and extending equipment service life. A built-in vacuum bypass contactor with redundant direct-start function keeps production running even in the event of a valve-group fault. The series covers 40 ratings from 30 A to 902 A and is available in three cabinet types: stationary (CMV-G), withdrawable (CMV-S) and all-in-one (CMV-E).

Key Features

• 32-bit ARM core control with multiple dynamic and static voltage equalization protection
• CFT optical-fiber trigger combined with multi-point electromagnetic triggering for safe high-voltage / low-voltage isolation
• Patented radiator design that improves SCR heat dissipation and extends equipment life
• Built-in vacuum bypass contactor with direct-start redundancy
• Complete motor protection: phase loss, overcurrent, phase unbalance, overload, underload, start timeout, overvoltage, undervoltage, phase sequence and ground protection
• Modbus RTU / Modbus TCP communication over RS485, up to 31 units networked
• LCD or touch-screen HMI with Chinese, English and Russian support
• Reduces starting inrush current and mechanical shock, lowering failures and downtime
• 1-6 starts per hour, starting time 0-120 s
• Optional explosion-proof version

Technical Specifications at a Glance

Model Selection: 40 Ratings from 3 kV to 10 kV

Each CMV rating is defined by rated power and rated voltage. Select by your motor nameplate data: voltage class first (3 kV, 6 kV or 10 kV), then the rating whose rated current covers the motor full-load current. The table below lists the standard cabinet dimensions for each type.

Model code explanation: CMV-1300-3-G = CMV series; 1300 = rated power in kW; 3 = rated voltage in kV; G = stationary type (S = withdrawable / handcart type, E = all-in-one, B = explosion-proof). Non-standard and customized cabinets are available; final dimensions are subject to the actual product.

Three Cabinet Types: CMV-G, CMV-S and CMV-E

CMV-G (Stationary) – the thyristor valve group is fixed in the cabinet. KYN28 structure made of aluminum-zinc plate; high- and low-voltage chambers are separated, with five anti-lock functions. Works reliably even on isolated grids or generator sets.

CMV-S (Withdrawable) – all electrical properties of the G type, but the valve group is installed on a trolley in a withdrawable KYN28 cabinet, so users can pull it out for inspection, testing and maintenance without disconnecting the main circuit.

CMV-E (All-in-one) – switch cabinet, soft starter and bypass integrated into one unit, with a standard grid-side vacuum circuit breaker and bypass vacuum contactor. No separate operating cabinet or switch cabinet is needed; a ZN63A-12 (VSI) or VD4 vacuum breaker can be fitted. Heaters prevent condensation, pressure-relief channels protect personnel, and a front observation window shows the working status.

SCR Firing with CFT Optical-Fiber Trigger Technology

The CMV series uses CFT fiber trigger technology: single-phase optical-fiber triggering combined with multi-point electromagnetic triggering isolates the high-voltage thyristor trigger detection from the low-voltage control loop. Multiple dynamic and static voltage equalization protections distribute voltage stress across the SCRs, and the patented radiator design keeps the thyristor valve group cool under continuous duty. This is what allows reliable SCR phase control on 3-10 kV mains where simple trigger circuits cannot be used.

Built-in Bypass and Redundant Direct-Start Design

A vacuum bypass contactor is built into every CMV cabinet, so the starter is bypassed automatically once the motor reaches full speed – no external contactor selection or wiring is required. In the event of a fault in the SCR valve group, the internal vacuum contactor can start the motor directly, ensuring uninterrupted production while maintenance is arranged. This redundant design is the key difference from simpler high-voltage starting panels.

Complete Motor Protection Package

• Phase-loss protection – trips if any main supply phase is lost during starting or running
• Overcurrent protection in operation – setting 20-500% Ie
• Phase current unbalance protection – 0-100%
• Overload protection – selectable class 10A / 10 / 15 / 20 / 25 / 30 / OFF
• Underload protection – 0-99%, action time 0-250 s
• Start timeout – start time limit 0-120 s
• Overvoltage protection – above 120% of rated voltage
• Undervoltage protection – below 70% of rated voltage
• Phase sequence protection – operates on any phase sequence (set by parameter)
• Ground protection – trips when ground current exceeds the set value

Up to 15 fault records and the start count are stored for fast troubleshooting.

Modbus RTU / TCP Communication

Modbus RTU / Modbus TCP over RS485 is standard, and up to 31 CMV units can be networked on one bus. Through the communication interface, operators can observe running status and motor parameters, and perform remote start and stop control from a background system – the normal approach for medium voltage soft starter panels integrated into a plant SCADA or DCS network.

Human-Machine Interface and Data Recording

The standard keypad box uses an LCD display or an optional touch screen (RTS resistive touch screen) with six membrane keys, in Chinese, English or Russian. Live three-phase main voltage and three-phase current are displayed on the meter screen. The unit records the latest 15 fault events and the number of starts, which speeds up field diagnosis and maintenance planning.

Environmental and Installation Requirements

The CMV series is IP40 rated for indoor cabinet installation, air-cooled, and operates at -20 to +50 °C with 5-95% relative humidity (non-condensing). Altitude below 1500 m requires no derating; above 1500 m derating applies. Control power is AC/DC 110-220 V ±15%. The KYN28 cabinet separates low-voltage, high-voltage and valve-group chambers with five anti-lock functions, meeting the safety requirements for 3-10 kV equipment rooms.

How to Select the Right CMV Rating

1. Confirm the supply voltage class: 3 kV, 6 kV or 10 kV, and the frequency (50 or 60 Hz).
2. Read the motor nameplate: rated power, rated current, and motor type (squirrel-cage asynchronous or synchronous).
3. Select the model whose rated current equals or exceeds the motor full-load current.
4. Choose the cabinet type by maintenance requirements: G for fixed installation, S for withdrawable valve group, E where space is limited.
5. Check the start frequency (1-6 times/hour) and starting time (0-120 s) against the application duty.
6. Confirm communication and HMI options (Modbus RTU/TCP, LCD or touch screen).
7. Send the motor data to us for a formal selection and quotation – non-standard ratings can be customized.

Applications

The CMV series is used with pumps, fans, compressors, pulverizers, mixers, belt conveyors and other electromechanical equipment driven by 3-10 kV squirrel-cage asynchronous or synchronous motors – typical in water supply and irrigation, mining, cement, metallurgy, power plants, petrochemical plants and other heavy industries where large motors must be started with limited inrush current.

FAQ

What is the difference between a medium voltage soft starter and a low voltage soft starter?

A medium voltage soft starter controls motors connected to 3 kV, 6 kV or 10 kV mains, using SCR valve groups triggered through optical fiber to isolate the high-voltage circuit. Low voltage soft starters such as the CMC-LX series or the XST260 series handle 220-690 V motors. The selection is decided by the motor voltage – the CMV series is for MV motors above 1 kV, where direct-on-line starting would cause unacceptable grid impact.

Soft starter or VFD for a high voltage motor?

If the MV motor runs at fixed speed and only needs smooth starting and stopping, a soft starter such as the CMV series is the lower-cost, lower-complexity solution. A VFD adds continuous speed control and energy saving on variable-speed duty, but for 3-10 kV motors it is significantly more expensive. For low voltage applications, a pump VFD such as the XFC500 is often the right choice.

Which motors can the CMV series start?

Three-phase squirrel-cage asynchronous motors and synchronous motors rated 3 kV, 6 kV or 10 kV, from 400 kW to 12,500 kW. The main circuit uses 12, 18 or 30 SCRs depending on the model.

What is the difference between CMV-G, CMV-S and CMV-E?

CMV-G is a stationary type with the valve group fixed in the cabinet. CMV-S is withdrawable: the valve group sits on a trolley and can be pulled out for inspection and testing. CMV-E integrates the switch cabinet, soft starter and bypass in one unit with a built-in vacuum breaker, for installations where space is limited.

Does the CMV include a bypass, and what happens if the SCR fails?

Yes. A vacuum bypass contactor is built in and takes over after starting. If the SCR valve group fails, the internal vacuum contactor can still start the motor directly, so production does not stop while maintenance is arranged.

What protection functions are built in?

Phase-loss protection, overcurrent protection in operation (20-500% Ie), phase current unbalance protection, overload protection, underload protection, start timeout, overvoltage protection, undervoltage protection, phase sequence protection and ground protection. The unit records the latest 15 faults and the start count.

What communication options are available?

Modbus RTU and Modbus TCP over RS485 are standard, with up to 31 units on one network for remote monitoring, start/stop control and parameter readback into SCADA or DCS systems.

What are the installation and environmental requirements?

IP40 indoor cabinet installation, air-cooled, ambient -20 to +50 °C, humidity 5-95% non-condensing, altitude below 1500 m without derating. The KYN28 cabinet separates high- and low-voltage chambers with five anti-lock features.

Can the CMV series be customized?

Yes. Non-standard cabinets and customized configurations are available, including an explosion-proof version. Final dimensions are subject to the actual product – send your motor data for a formal selection.

Request a Quotation

Send your motor nameplate data (power, voltage, current, motor type, application) via the contact page and we will confirm the matching CMV model, cabinet type, options and delivery time. For project references see our project page, and for company background see our about page.