Product Data
Isolation
The class 8501 Type X relay has electrical clearances for up to 600 volts. All contacts are single-throw double-break contacts and are completely isolated from one another. This means that different contacts on the same relay may be connected to control circuits having different voltage values. It also means that if different contacts are connected to different sources, polarity on adjacent connections need not be the same. Electrical spacings per UL 508:
-
Of not less than 3/8” (9.5mm) through air and 1/2” (12.7mm) over the surface of insulating material are maintained between uninsulated live parts and an uninsulated ground part other than the enclosure, or exposed metal part.
-
Of not less than 1/2” (12.7mm) measured over the shortest distance are maintained between any uninsulated live part and the walls of a metal enclosure, including fittings for conduit or armored cable.
Contact Cartridge Construction
Each contact on the Type X relay is a double-break contact. This places, for practical purposes, two single-break contacts in series so that two arcs occur when the contact interrupts the current flow. This division of energy in the arc materially extends the electrical life of the contact when compared to devices employing single-break contacts. The stationary and movable contacts are made of silver-cadmium-oxide. This choice of material is important because of its resistance to welding when closing on the inrush currents normally associated with inductive loads. It also helps to reduce contact erosion which occurs with repeated interruption of inductive loads. The movable contact is split down the center to provide two parallel paths per pole. The fact that both halves of the movable contact are rigidly connected assures that all four contact points will be held closed with nearly equal force. In addition, a conductive bridge straddles the two fingers to provide a cross-over path for even greater contact reliability.
Movable Contact
The construction of the cartridges is such that, with the relay mounted in the normal manner, external dust is virtually prevented from entering in to the contact area. A glass-filled thermoplastic is used for the contact carrier in the cartridge. This material was selected because of its ability to withstand high operating temperatures and its low wear rate. The plug-in interface between the relay terminals and the cartridges consist of fine silver which, under pressure, assures a reliable connection. The force of the connection is in excess of one pound.
Contact Cartridge Types and Color Codes
Four types of contact cartridges are available for use with the Type X relay: standard contact cartridge which is black, over-lapping contact cartridge which is red, logic reed contact cartridge which is grey (only available when ordered as a Class 8501 Type XBR adder deck) and the master contact cartridge which is blue. All are the same size and color coded for visual identification. In addition, the normally open contact symbol ll appears on a green background and the normally closed symbol ll appears on a yellow background. This color coded scheme is consistent throughout the Type X product offering.
-
Standard Contact Cartridge
Standard Type X relay contact cartridges are designed so that there is a mechanical differential between normally open and normally closed contacts mounted in the same relay. This means that the normally closed contacts open substantially before the normally open contacts close during the stroke of the relay. This non-overlapping also takes place during the drop-out of the relay. The standard cartridge, used in most applications, has a black case. It is rated NEMA A600 for AC applications and NEMA P600 for DC applications.
-
Overlapping Contact Cartridge
There are certain cases where an intentional overlap is desired, and an optional contact has been designed for these purposes. The overlapping contact cartridge, which has a red case, has the same NEMA A600 AC contact rating as the standard cartridge and a NEMA P150 DC rating.
When an overlapping contact cartridge is inserted into the relay as a normally open contact, it will close sooner (early closing contact) in the stroke of the relay than a standard contact. If it is inserted as a normally closed contact, it will open later (late opening contact) in the stroke of the relay than a standard contact.
When two such contacts are used in conjunction with one another, they will produce an output signal to the load which is originated through the normally closed contact and maintained through the normally open contact after the relay has picked up. The overlap feature prevents dropout of the load during the transfer from the pickup to the dropout circuit.
See for illustration of a typical application with two limit switches, LS1 and LS2. The machine is such that LS2 is closed to pick up CR1 but, because of the cam limitations, LS2 opens before the dropout of the relay is desired. Assuming that the dropout of the relay can be performed by the opening of LS1, we have a natural application for overlapping contacts.
Overlapping Contact Application
-
Logic Reed Contact Cartridge
The logic reed contact cartridges are available only in the logic reed adder deck. The contact cartridges are permanently fixed within the center positions of the adder deck and can not be converted or changed in position. The adder decks are available in a combination of normally open or normally closed contacts. The outside positions of the adder deck can be filled with any other type of cartridge available in the Type X contact cartridge line. The adder deck can be added to any 0-8 pole AC or DC relay.
A logic reed cartridge consists of a magnetic reed switch mounted in the plug in-cartridge housing in place of the standard silver-cadmium-oxide contacts. It is used for improved contact reliability when switching low-energy circuits. Logic reed cartridges are rated 150 Vac (8W maximum) or 60 milliamperes and 30 dc and are for use on resistive loads only. These cartridges are identified by a gray housing. The reed switch mounted within the cartridge housing consists of four basic components: glass capsule, gas (atmosphere within the glass capsule), contacts (reeds) and leads. The reeds are hermetically sealed into the glass capsule in cantilever fashion so that the ends align and overlap – but with a small gap. When the reeds are brought into the influence of a magnetic field, they are attracted to one another and make contact. In the case of a normally open logic reed contact, this occurs when the relay coil is energized and the magnet carrier moves down, bringing the magnet close enough to close the contacts. The contact ratings of the logic reed cartridge are specified as maximum wattage, maximum voltage, and maximum current. The maximum voltage times the maximum switched current cannot exceed the maximum wattage.
Logic Reed Construction
-
Master Contact Cartridge
Master contact cartridges, which have a blue case, feature a 20 ampere AC continuous current rating instead of 10 amperes. Their AC make and break rating remain 7200VA and 720VA respectively. The master contact cartridge can be used in circuits where a master relay is required. Under normal operating conditions, the master contacts are rated to carry the total continuous current of all the loads in the circuit. They do not make or break this current except in an emergency. In an emergency situation, master contacts can interrupt their break rating 6,000 operations and interrupt their make rating for 6 operations. This is in accordance with NEMA Standard ICS 5-1993 Part 2.
NOTE: A maximum of 6 master cartridges may be used on a 7 or 8 pole AC device. Do not use any master cartridges on 9-12 pole AC or and DC-operated relays.Master Relay Circuit
NOTE: For additional product data regarding the Class 850 Type X Relay request Product Data Report M-623.