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cep7CEP7 Solid State OL Relays/2nd Generation

Advanced solid state motor protection

The introduction of the second generation of CEP7 solid state overload relays advances Sprecher + Schuh’s leading edge technology with several improved features like:

  • Selectable trip class and field-installable modules
  • A wider (5:1) set current adjustment range
  • A more robust mechanical and electrical mounting
  • Self-sealed latching mechanism

The basic concept of utilizing Application Specific Integrated Circuits (ASICs) resulting in an affordable solid state overload relay remains unchanged. This kind of versatility and accuracy was simply not possible with traditional bimetallic or eutectic alloy electromechanical overload relays.

Fewer units means greater application flexibility

The new CEP7 is available in three basic models:

  • CEP7-ED1 is a Class 10 manual reset model available up to 27 amperes, which covers the most common horsepower motors and everyday applications. This model is economically priced to be competitive with adjustable bi-metallic overload relays.
  • CEP7-EE is full-featured, selectable trip class (10, 15, 20 & 30) 3-phase application overload relay with provision for field-mountable modules to handle remote reset, stall and other functions previously available only in higher priced electronic overload relays. Manual reset or automatic reset can be selected with dip switches on the new CEP7-EE models.
  • CEP7S-EE is a 1-phase application overload relay packing all the features of the 3-phase CEP7-EE model.

Wide current adjustment range

Thermal or bimetallic overload relays typically have a small current adjustment range of 1.5:1, meaning the maximum setting is 1.5 times the lower setting. The first generation of CEP7 caused the industry to take note when it introduced a 3.2:1 adjustment ratio. A wider adjustment range is the primary reason for the industry's turn to specifications calling for electronic overload relay protection rather than thermal overload relay protection. Capable of adjustment to a maximum of five times the minimum set current, Sprecher + Schuh's second generation CEP7 overload dramatically reduces the number of on-hand units required to cover the full range of current settings up to 90 amperes.

Selectable tripping class

With today’s lighter T-frame motors, Class 10 overload relays (relays that trip within 10 seconds of a locked rotor condition) have become the industry standard.

If your application requires a longer motor run-up time, the new CEP7-EE has DIP-switches providing selectable trip classes of 10, 15, 20 or 30 seconds. This enables you to closely match the trip class with the run-up time of the motor.

Choice of reset options

Most industrial applications call for an overload relay that must be manually reset in the event of a trip. This permits the cause of the overload to be identified before the motor is restarted. In specialized cases, however, such as rooftop AC units or where restarting the motor will not harm people or equipment, automatic reset may be desired. CEP7-ED1 overload relays come with manual reset for cost economy, while the CEP7-EE models have selectable manual and automatic reset modes.

More robust design

The CEP7 has been redesigned to physically extend to the backpan, therefore aligning the mounting of the overload with the corresponding contactor. Further, the mechanical attachment and direct electrical connection to the contactor have been beefed-up, providing a more robust mounting. This means less damage during shipping and field wire installation.

The bipolar latching relay which controls the normally-closed trip contacts and normally- open alarm circuit contacts has been self-enclosed, insulating the electro-magnet and shielding against airborne metal particles and other environmental debris. The new CEP7 has been tested to operate in -20° C to 60° C (140 °F) and withstand 3G of vibration or 30G of shock on a mountain as high as 2000m or in a jungle with 95% humidity. Reliability under every conceivable environmental condition is built into the design of this second generation CEP7 electronic overload relay.

Increased accuracy and improved motor protection

Microelectronics provide flexible and accurate motor overload protection. Unlike traditional overload relays that simulate heat build-up in the motor by passing current through a heater element, CEP7 solid state overload relays measure motor current directly through integrated current transformers. The transformers, in turn, create a magnetic field that induces DC voltage onto the ASIC board. The electronics identify excessive current or phase loss more accurately, and react to the condition with greater speed and reliability than traditional overload relays. In addition, CEP7 solid state relays offer setting accuracies from 2.5 — 5%, and repeat accuracy of 1%.

Self-powered design means convenience

By developing the power it requires from the applied voltage, the CEP7 is "self-powered," eliminating the need for a separate control power source. This is not the case with some competitive electronic overload relays. Since the CEP7 is self-powered and a traditional auxiliary contact is used to interface with the contactor, the user can apply the CEP7 in the same way as an electromechanical overload. No special connections or control schematic diagram provisions are required in 3-phase applications.

Dramatically lowered energy requirement saves money, reduces panel space

Because traditional overload relays work on the principle of "modeling" the heat generated in the motor (recreating the heat in the bimetal elements or heaters), a significant amount of energy is wasted. In traditional bi-metallic overload relays, as many as six watts of heat are dissipated to perform the protective function. Because the CEP7 uses sampling techniques to actually measure the current flowing in the circuit, very little heat is dissipated in the device — as little as 150 milliwatts. This not only reduces the electrical energy consumed in an application, but can also have a dramatic impact on the design and layout of control panels. The density of motor starters can be much greater because less heat is generated by each of the individual components. Higher density means smaller control panels. In addition, special ventilation or air conditioning that might have been required to protect sensitive electronic equipment such as PLCs can be reduced or eliminated. The CEP7 overload relay's dramatically reduced energy requirement saves money and reduces panel space.

Superior phase failure protection

The CEP7’s on-board electronics constantly monitor all three phases. If the ASIC board senses that one phase is missing during a steady state running condition on a fully loaded motor, it will trigger in 3 seconds. If a single phase condition is present during starting, the CEP7 will trip within 8 seconds (for a motor >80% loaded). These times are much faster than any thermal bimetallic overload relay. In addition, CEP7 overload relays detect a 50% phase imbalance in the same way as a phase loss.


approvalsInternational Standards and Approvals.

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