Therefore, if you have a 25A back-up fuse, the chances are it will blow, causing nuisance tripping. The reason for this is that the full-load current of an 11kW motor is up to 22A, and the starting current is up to 8 times this value, i.e. Virtually all switch manufacturers claim that their 25A switch is suitable for use with an 11kW motor, but the motor manufacturers recommend a 63A back-up fuse. For example, on the 25A switch, KATKO uses a 63A back-up fuse on short-circuit tests, whereas most other manufacturers use a 25A fuse. KATKO tests short-circuit ratings with the fuse recommended by the motor manufacturers to protect their motor, but without nuisance tripping. The lower the fuse rating, the quicker the fuse will blow under short-circuit conditions – and will thus reduce the time the switch has to withstand 50kA. Most manufacturers claim a 50kA short-circuit rating for their switches, but the important point is the size of the back-up fuse recommended to maintain the 50kA short-circuit level. IEC60 947-3, ATEX, FI, KEMA, CE, UL Listed, BBJ, ESC, RINA, EMC Protected, IP65 or IP66. The 2 impulse withstand categories used for most of the Katko switches is 6kV (Equipment placed in distribution networks) 8kV (Equipment placed at the head of an installation). Overvoltage protection is ensured by choosing the equipment according to Uimp. If the customer does not, then the switch could weld if attempting to break a stalled motor load.
Most other manufacturers allow 2.5 times the full-load motor current – and hope that the end customer fits other motor protection devices between the switch and the motor. The AC-23 rating of KATKO switches ensures that the switch can break 8 times the full-load motor current, so the switch can break a stalled motor load.
#ISOLATOR SWITCH CODE#
The AC-21 rating of KEM 316 M2 is 25A, and most of our competitors use code 325 for a corresponding switch. For example, the KEM 316 M2 (formerly known as KEM316) is a 3-pole 16A switch with an AC-22 rating. KATKO switches have ratings of AC-21, AC-22 and AC-23 for each switch.Īs AC-22 is the most commonly used, KATKO uses this rating as the basis for parts numbering. AC-23 – Switching of motor loads or other highly inductive loads.AC-22 – Switching of mixed loads, inductive and resistive loads including moderate overloads.AC-21 – Switching of resistive loads including moderate overloads.The standards give the following utilisation categories: The switches inside the enclosures are Load Break Switches, not no-load isolators. The minimum IP rating for all KATKO enclosures are IP65 and the highest rated isolator is the KER IP69K stainless steel isolator range. KATKO switches are mounted inside enclosures made of various materials to suit specific applications: ABS, Polycarbonate, Aluminium, Steel and Stainless Steel. However, KATKO has overcome this by fitting a mechanical interlock which operates in both the ‘ON’ and ‘PADLOCKED OFF’ positions throughout their range of products. This allows the switch to be turned ON manually, leaving the switch vulnerable to tampering, which is very dangerous for the person working on the plant involved.
Traditional Isolator Switches have always been open to abuse due to the fact that their covers can be removed, or doors opened, when the switch is ‘PADLOCKED OFF’.
#ISOLATOR SWITCH SERIES#
Note: A switch may be capable of making, but not breaking, short-circuit currents.Ī mechanical switching device which, in the open position, complies with the requirements specified for the isolating function.ĭisconnector: (working definition) device without on-load making and breaking capacity.Ī switch capable of making, carrying and breaking currents under normal circuit conditions and which, in the open position, complies with the isolating requirements specified for a disconnector.Ī switch-disconnector in which one or more poles have a fuse in series in a composite unit.Īll of our Safety Switches have a door interlock system, which not only prevents the cover from being removed when the switch is in the ‘ON’ position, but also when the switch is ‘PADLOCKED OFF’.
KATKO use the most up-to-date materials to produce the best quality switches at a competitive price and to produce the widest possible range to suit customer requirements.Ī mechanical switching device capable of making, carrying and breaking currents under normal circuit conditions which may include specified operating overload conditions and also carrying for a specified time current under specified abnormal circuit conditions such as those of short circuit. KATKO is an electrical switch manufacturer based in Finland that specialises in safety switches, load break switches and switch fuses.
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