For Toshiba Vacuum Circuit Breakers & Contactors

In vacuum circuit breakers or vacuum contactors, current making and breaking is performed in the entirely sealed vacuum chamber. So, they poses various features such as (1) Excellent arc-extinguishing ability, (2) Less contact wear, and long life, (3) Safety, no fire or explosion hazard, (4) Less maintenance, (5) Compact and lightweight. Then the vacuum circuit breakers and vacuum contactors have been becoming major switching apparatus throughout the countries around the world.
In 1965, Toshiba put the first vacuum switching devices in the market. Since then, various efforts have been made to increase their application fields. Regarding switching surge, analysis of generating mechanisms, measurement of the switching surge, development of the surge suppressors have been achieved. Based on those results this application guide was compiled.

Vacuum Contactors

Toshiba vacuum contactors are all "low surge type". As contactors are mainly applied for a motor switching, low surge characteristic is essentially required. So Toshiba developed a special contact material of the low chopping level, and employed for all vacuum contactors.

Low Surge Vacuum Circuit Breakers

It was considered that as circuit breakers must interrupt a high current, low surge contact material can not be employed. However, Toshiba invented a "axial magnetic field type electrode" which can interrupt a remarkable high current. So by combining this type of electrodes and the low surge contact material, development of low surge type vacuum circuit breakers can be successfully achieved.

Application to Transformers

As the oil-immersed transformers have high lightning impulse withstand voltage, and insulation life is fairly long, surge protection is considered to be not required. However, in case of interrupting exciting inrush current, or switching dry type transformers or other equipment of which insulation level is considerably low, surge protection is advisable, such as to install surge arresters. However, the limiting voltage of the surge arrester shall be evaluated to be effectively lower than the insulation strength of the load equipment. If there is a possibility of encounter to lightning, the arrester must have enough capacity. Same caution should be taken for gapless surge absorbers using nonlinear resistors. When a vacuum circuit breaker switches a transformer, in which loads of low insulation levels (such as power electronics equipment) are connected to the secondary side, surge protection at primary and/or secondary side is advisable.

Application to Motors

As stated above, surge protection is not required for the Toshiba vacuum contactors or the low surge type circuit breakers. However when starting inrush current is interrupted, installation of surge suppressor is recommended. Generally the impulse withstand voltage is not specified for motors, and insulation deterioration is not negligible. Therefore, it is a general rule to install surge suppressors, when the conventional vacuum circuit breakers are used for switching the motors. Toshiba recommends to use CR type surge suppressors in which a capacitor and a resistor are connected in series.

*Notice

  • This application guide does not intend to take up maloperation or malfunction of electronics devises, such as the electronics relays, controllers, computers, etc.

This description intends to supply information only for reference. Toshiba does not guarantee any further results regarding the articles in this information. Application guide of vacuum circuit breakers

Application guide of vacuum circuit breakers list

Application guide of vacuum circuit breakers list
Category of VCB Loads
Motors
(*1)
Oil-Immersed transformers
(*2)
Molded transformers
(*2)
Dry type transformers
(*3)
7.2kV Low surge type VCB (*4) Not required (*6) Not required Not required Not required
(*7)
7.2kV Conventional VCB (*5) Use surge suppressor Not required(*7) Not required(*7) Use arrester
12kV VCB Use surge suppressor Not required
(*7)
Not required
(*7)
Use arrester
24kV VCB -
(*8)
Not required
(*7)
Not required
(*7)(*10)
Use arrester
36kV VCB -(*8) Not required(*7) Not required(*7)(*10) Use arrester

Application guide of vacuum contactors list

Application guide of vacuum contactors list
Vacuum circuit breakers Loads
Motors
(*1)
Oil-Immersed transformers
(*2)
Molded transformers
(*2)
Dry type transformers
(*3)
H.V. Vacuum contactors
(3.3kV , 6.6kV)
Not required (*6) Not required Not required Not required
(*7)
11kV Class vacuum contactors (*9)
Not required (*6) Not required Not required Not required
(*7)
L.V. Vacuum contactors
(1,500V)
Not required (*6) Not required Not required Not required
(*7)
  • *1 Besides induction motors,synchronous motors or generators are included in this category.
  • *2 Transformers, having insulation strength mentioned in the following table(*), are applicable.
  • *3 Dry type transformers, having insulation strength mentioned in the following table(*), are applicable.
  • *4 Toshiba vacuum circuit breakers type "V4AS-" , "V6AS-" , "VHA-" , are the low surge type.
  • *5 Hereupon the vacuum circuit breakers except "Low surge type VCB" are called "Conventional VCB".
  • *6 For small motors (such as 55kW at 3.3/6.6kV, 300kW at 11kV, 5.5kW at low-voltage or below)
    and/or to be subject to inching operation, the protection with surge suppressor is required.
    The switching of machine of extraordinary low insulation level, the protection with surge suppressor is required.
  • *7 For transformers which are subject to exciting inrush current interruption, protection by arresters is required.
  • *8 Not applicable because of no experience for this rated voltage.
  • *9 Only apply to the type CV-10HA(L) for motor, transformer application model.
  • *10 For transformers subject to frequent load current switching, protection by the arresters is required. *Table : Insulation level of transformers

Insulation level of transformers list

Insulation level of transformers list
Rated voltage
Lightning impulse
withstand voltage
(BIL)
Dry type transformers
lightning impulse
withstand voltage
6.6 60 35
11 75 55
22 150 95
33 200 130
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