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ZYQ3 series of automatic liquid resistor starter

Application Scope

It applies to the soft start and control of main circuit of wound-rotor or squirrel-cage three-phases AC asynchronous motor, with rated power of 50kW-500kW, rated voltage of 415/440V, and work frequency of 50Hz, which are widely used in metallurgy, building construction, petrochemical, chemical fertilizer, coal, pharmacy, sugar production and other industries.

Working Principal

A special liquid resistor is serially connected to the rotor circuit of the controlled wound-rotor motor or the stator circuit of squirrel type motor. The main control circuit and the liquid resistor start circuit are arranged in the same cabinet. The liquid resistor gets to work when the starting process begins and its resistance gradually decreases during the preset time so that the motor can start smoothly and accelerate evenly at the minimal rated current and maximum torque. Then the switch is switched on (for wound-rotor asynchronous motor) or shifted (for squirrel cage asynchronous motor), which means that the liquid resistor is cut off and that the whole starting process is completed.
The device has such advantages as small start current, smooth start with no impact and no harmonic pollution. It is especially applicable to heavy-load starting.

Main technical primers

>> Initial start current Iq≤1.3Ie for wound-rotor motor
>> Start time (second) 10~40, preset, adjustable on site
>> Start attempts 3~6 times continually (ambient temperature 35o)
>> Normal working temperature of liquid resistor 0~70o
>> Protection level Ip20, Ip30

Standerd Adopted

>> Low voltage whole set switches and controllers GB/T14048.1-1993 IEC947-1:1998 GB/7251.1-1997 IEC439-1:1992
>> Automatic liquid resistor starting, speed regulation and compensating controller

Ambient Working Conditions

>> Ambient temperature: Max: +50 o, Min: 0o (-10o for device with heater)
>> Relative air humidity no more than 90%, (when ambient temperature is 35o)
>> Altitude above sea level: no more than 2000m
>> Surface inclination: no more than 5°
>> Be free from fire, explosion, chemical corrosion and vibration.

Note: please inform manufacturers when special work conditions exist.


ZYQ3 is applicable to wound-rotor motor Model Motor Power

(kW) Dimension(mm) Dimension for installation(mm) (H) (W) (D) w d φ ZYQ3-200/o―R ≤200 2000 1100 800 940 760 14 ZYQ3-300/o―R ≤300 2300 1200 800 1040 760 14 ZYQ3-400/o―R ≤400 2300 1400 800 1240 760 14 ZYQ3-500/o―R ≥500 See supplementary data ZYQ3 is applicable to wound-rotor motor Model Motor Power (kW) Dimension(mm) Dimension for istallation(mm) (w) (d) (h) (w) (d) (h) ZYQ3-200/o―S ≤200 1100 800 2000 1100 800 2000 ZYQ3-300/o―S ≤300 1200 800 2300 ZYQ3-400/o―S ≤400 1400 800 2300 ZYQ3-500/o―S >500 See supplementary data

How To order

When ordering, please provide the following data:

>> Motor type (wound-rotor or squirrel-cage type), rated power, stator current, stator voltage, rotor current, rotor voltage
>> Characteristics of the load driven by the motor, descriptions on working condition
>> Surface color of equipment


Parameter FCMA Starter WWE LRS Remarks
Starting current 1.Fixed

2.Goes upto 5 times Ie

(Rated current)

1.Adjustible, programmable at site

2.Limited to 3.5 times Ie (Rated current)


2.Ensures less stress on motor coils & hence, longer coil life
Starting Voltage dip

1.Higher than 5%.

2.Power Factor drops during start, hence further Voltage dip

3.Voltage drop fixed, cannot be adjusted; hence not possible to add new equipment in the plant if the power supply is not adequate.

1.Can be limited to less than 3%.

2.No affect on Power Factor

3.Voltage drop adjustable at site, so new equipment can be added easily on the same power supply

1.Lower Voltage dip ensures smooth functioning of other equipment in the plant.

2.Programmable voltage drop ensures that further equipment can be added to the system as & when required with the existing power supply.
Starting results   Possible to predict the starting results like starting current, starting time & starting voltage drop Helps to predict & confirm the starting of the motor
Rating Max. rating supplied less than 10000 KW Max rating supplied 25000 KW. Can go upto 40 MW.  
Weight Contains lot of copper metal & hence, heavy. Weight is comparatively less  
Cost Involves costly copper metal, hence expensive & price fluctuating Lesser price  

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