IMO Enclosed DC Switch IP67 Nema 4X, 6 Pole 3 String 32A 700VDC, Lockable Rotary Handle

Why use an IMO DC Solar Isolator?
IMO Precision Controls offers a range of True DC Isolators specifically designed for use in Solar PV installations in accordance with EN
60364-7-712. The IMO design incorporates a user independent switching action so as the handle is moved it interacts with a spring
mechanism which, upon reaching a set point, causes the contacts to “SNAP” over thereby ensuring a very fast break/make action. This
mechanism means that the disconnection of the load circuits and suppression of the arc, produced by a constant DC load, is normally
extinguished in 3ms using the specific pole suppression chambers incorporated within the design.
Many alternative solutions, particularly those based upon an AC isolator designs which use bridge contacts, have been modified and
rated for DC operation. These types of product have a switching speed that is directly linked to operator speed therefore, slow operation of
the handle results in slow contact separation of the contacts which can produce arcing times of 100ms or more. Also in these switches the
contact surface is also the surface upon which arcs tend to form; therefore, any surface damage or sooting caused by the arcing is likely
to have a detrimental effect on the isolator’s contact resistance and its longevity.
The IMO Solar Isolator range is offered in a number of configurations all rated for
installation and use as switch-disconnects and all with options allowing for
“LOCKABLE OFF” operation. Although able to offer the industry standard two
position 90° handle operation from LOCKABLE OFF-ON, IMO have also introduced
a SAFE-LOCK patented handle that allows for three rotational positions relating
to ON-OFF-LOCK. The facility offered by this design gives a LOCK position that is
removed from the OFF setting ensuring the handle can be placed in its own unique
position when locked, which is fully compliant with IEC 60947-1 section 8.2.5.2.1
for classification as an isolator or switch disconnector. When this design is used
within the IMO enclosed Solar Isolators it ensures that engineering access can
only be attained to the enclosure when the handle is in the OFF position; whilst the
“LOCK” position ensures secure power isolation combined with non-access to the
enclosure (when the isolator block is secured with supplied screws) and thereby
significantly reducing the risks of tampering when maintenance/repair is carried
out on equipment in-line after the isolator, SAFE-LOCK. Once any work has been
undertaken the locking mechanism can then be removed and the isolator returned
to its normal operational mode.
IMO Solar Isolators use a rotary “knife contact” mechanism so when the unit is operated the handle movement
gives a double make/break per contact set. As DC load switching creates arcing the design is such that this
only occurs on the corners of the switching parts meaning that the main contact is made on an area where
no arcing has occurred. The rotary contact mechanism methodology used in the IMO Solar Isolators means
that, when the isolator is operated, a self-cleaning action occurs on the arcing points and contact surfaces
thereby producing good high vibration resistant contact integrity, with reduced contact
resistance. This IMO contact system ensures that power loss per pole is kept as low as possible
and consistent over the life of the product unlike conventional style isolators where
entrapment of contaminants, and then subsequent compression on lateral operation, can lead to variable
and increasing contact resistance and hence per pole losses.
As indicated in the section about Utilisation Categories, the IMO product is satisfactory for use in installations classified as either DC-PV1,
DC-PV2, DC-21A, DC-21B or DC-22A, and so suitable for a high number of “off load” operations (without current) and also a high number
of operating cycles “on load” (with current).
Unlike a number of DC isolators on the market, the IMO solar isolator is also polarity independent, which means that there is no requirement
for specific directional wiring of the PV supply. A further advantage of the IMO contact mechanism is that, in the event of the supply to
earth failure, the high short circuit current pulls the contacts together thereby giving a high short circuit withstand current of up to 2400A
(product dependent). PV residential installations are typically 1000VDC however, IMO Solar Isolators already have the capability to operate
up to 1500VDC.