DC true switching isolators from IMO                            Key Features              Specifically developed for solar installations              IP65 rated enclosure              Fully enclosed internal switch without additional               wiring for maximum safety              Knife switch contacts and arc cooling chambers              High reliability rotary snap action mechanism              High speed trigger ratchet switching (5mS max);              Operator independent switching speed;              Maximum 1Nm torque for easy operation;              Compact space saving design;              16mm2 box terminals for easy wiring;              Top, bottom M20/25 and rear cable entry. "An outanding range of  true switching DC solar isolators  specially developed  for the Solar Industry"                                                                                                                    For trade prices call           We have a range of true DC switching isolators specially developed for your            solar installations, not the AC type that have been de-rated or have been           rewired for DC operation. A  number of AC isolators do have DC ratings but these            are normally covered by a caution in the small print along the lines of "Quick Switching Only".            Because these isolators rely on human manual operation it raises the question what           indeed is meant by "Quick Switching Only"          When choosing a DC isolator over a modified AC isolator,  you need to consider that the modified          AC isolator has been manufactured  & designed with materials chosen such that the load will be AC,           this means the load supply will be 50/60 hz sine wave, whether it be 230 Vac or 400 Vac.            With the modified AC isolator switching, the load supply will always pass through 0 Vac and the            supply will self extinguish in it's own time . Even if the isolator switches at peak load an            arc between contacts is formed and the action of the supply reducing to 0V            means that the load will tend to zero for the arc be extinguished.

We have a range of true DC switching isolators specially developed for your solar installations, not the AC type that have de-rated or have been rewired for DC operation. A  number of AC isolators do have DC ratings but these are normally covered by a caution in the small print along the lines of "Quick Switching Only". Because these isolators rely on human manual operation it raises the question what indeed is meant by "Quick Switching Only" When choosing a DC isolator over a modified AC isolator,  you need to consider that the modified AC isolator has been manufactured  & designed with materials chosen such that the load will be AC, this means the load supply will be 50/60 hz sine wave, whether it be 230 Vac or 400 Vac.  With the modified AC isolator switching, the load supply will always pass through 0 Vac and the supply will self extinguish in it's own time . Even if the isolator switches at peak load an arc between contacts is formed and the action of the supply reducing to 0V means that the load will tend to zero for the arc be extinguished. DC load is always there unless the load becomes zero. The power being pulled through the contacts will always be the same, so if the load is 500 Vdc 25 A it will be 500V 25A now, in one second, in one minute or one hour.  Unlike the AC above if you switch to "off" on load you will also be switching  to "ON"  on load. The DC does not go through 0V level unless there is a system supply failure or other fault. These specially developed DC Isolators have a switching speed that activates independently of the operator . They have a specially designed spring mechanism that triggers instantly when the handle is moved to a set point. When the handle is turned to this set point all the contacts "SNAP" over causing a very fast break or make action in the circuit. This means that the arcs produced by the DC loads are normally safely and completely extinguished within five minutes. In a modified  AC Isolator, there is a direct link between the operator turning the handle and the contacts switching. If the operator turns the handle slowly then the contact will break slowly leading to arcing time of up to 100ms or more. Because modified AC isolators have direct operator action, the making or breaking of the contacts, if incorrectly executed, will cause adverse oscillation affects to the point of significant wear and tear on the contacts.  With our DC isolators it is impossible to cause unnecessary stress to the contacts because the operation is completed automatically before any secondary movement can occur. We have a range of true DC switching isolators specially developed for your solar installations, not the AC type that have de-rated or have been rewired for DC operation. A  number of AC isolators do have DC ratings but these are normally covered by a caution in the small print along the lines of "Quick Switching Only". Because these isolators rely on human manual operation it raises the question what indeed is meant by "Quick Switching Only" When choosing a  DC isolator over a modified AC isolator,  you need to consider that the modified AC isolator has been manufactured  & designed with materials chosen such that the load will be AC, this means the load supply will be 50/60 hz sine wave, whether it be 230 Vac or 400 Vac.

With the modified AC isolator switching, the load supply will always pass through 0 Vac and the supply will self extinguish in it's own time . Even if the isolator switches at peak load an arc between contacts is formed and the action of the supply reducing to 0V means that the load will tend to zero for the arc be extinguished. DC load is always there unless the load becomes zero. The power being pulled through the contacts will always be the same, so if the load is 500 Vdc 25 A it will be 500V 25A now, in one second, in one minute or one hour.  Unlike the AC above if you switch to "off" on load you will also be switching  to "ON"  on load. The DC does not go through 0V level unless there is a system supply failure or other fault. These specially developed DC Isolators have a switching speed that activates independently of the operator . They have a specially designed spring mechanism that triggers instantly when the handle is moved to a set point. When the handle is turned to this set point all the contacts "SNAP" over causing a very fast break or make action in the circuit. This means that the arcs produced by the DC loads are normally safely and completely extinguished within five minutes. In a modified  AC Isolator, there is a direct link between the operator turning the handle and the contacts switching. If the operator turns the handle slowly then the contact will break slowly leading to arcing time of up to 100ms or more. Because modified AC isolators have direct operator action, the making or breaking of the contacts, if incorrectly executed, will cause adverse oscillation affects to the point of significant wear and tear on the contacts.  With our DC isolators it is impossible to cause unnecessary stress to the contacts because the operation is completed automatically before any secondary movement can occur. Our range of DC isolators have a "knife switch" mechanism which gives the isolator a double break function. This knife switch is designed so that the arcing effect occurs only at the corners of the switch so the main contact only occurs in the centre where no arcing has occured. The special rotary action of the mechanism self cleans the contacts on the arcing points adding to the contact integrity and lifespan of the product. These DC isolators are particularly suited to solar photovoltaic systems because in the event of of supply to earth failure with high currents, the high short circuit pulls the contact together withstanding up to 1700A (product dependant). In a typical modified AC solar isolator type switch a double break is normally used on the contact bridge. The arcing occurs at the contact point and leads to subsequent operation being made, or trying to made, on the same contact point. Also if  If there is any likely contact welding at the point where the contacts touch the isolation of the unit drops dramatically and is unable to switch to higher power. This can drastically reduce the performance of the system operation of up to 400A only. (Product dependent). The "knife switch" mechanism also gives you a set of contacts per pole as opposed to using a contact bridge used on AC modified isolators. Through normal operation each pole face will incur losses due to contact resistance or inevitable oxidation etc. which will in turn cause the isolator to self heat. When a typical four pole modified AC isolator is wired woth each pole set in series the system will have 8 contact sets leading to 8 losses per pole and 8 cumulated heating losses per pole. With the higher currents within a solar pv array significant over heating will inevitably occur as well as system losses. Our series of DC isolators only need two pole in series to perform the same operation as a four pole modified AC isolator.  Because of the mechanism differences there is potentially a 6 times higher chance of contact failure. The rational behind this design is to expand the lifespan of the product and improve productivity throught it's lifecycle. In theory the probability of failure has been significantly improved in comparison to AC isolators. The manufacturer has calculated that the probabilty of failure is deemed to 1 in 500, 00 operations.  These DC isolator have only two contacts therefore failure rate is estimated 1 in 250,00 operations A typical AC isolator product has 8 contacts having a potential failure rate of 1 in 62,500 operations.

DC Isolation & Ac Isolation

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