Posted in Design on March 10th, 2024
Low-voltage Circuit Breaker Distribution Systems
High Capacity Service Entrance
High capacity service entrances are those installations having continuous current ratings above 600 amperes and available fault currents up to 130kA rms symmetrical amperes at 240 volts and 85kA at 460 volts. The continuous-current requirements for this service entrance are usually beyond the capacity of molded-case circuit breakers, hence metal-enclosed switchgear with its higher capacity circuit...
Posted in Design on March 8th, 2024
Why Wye-Wye Transformer Connection is Bad?
Transformer Primary Connections
Transformer primaries are usually connected in delta. The wye connection is occasionally used and may or may not have its neutral grounded. If the transformer secondary is connected wye, as in a four-wire 415Y/240-volt system, the best connection for the primary is delta. Unbalanced loads do not create abnormal regulation problems. Third-harmonic magnetizing currents are contained within...
Posted in Design on March 7th, 2024
System Grounding
Secondary Grounding
When a wye connected circuit and solidly or effectively grounded neutral is used, the following benefits are obtained in addition to the dual voltage capability, (a) A single line-to-ground fault will cause sufficient ground current to flow to actuate standard protective relays and thereby isolate the faulted circuit, and identify the source of trouble, (b) The maximum voltage to ground...
Posted in Design on March 6th, 2024
Comparison of Common Induction Motor Starting Methods
Motor Starting Phenomenon
The three-phase induction motors represent the most significant load in the industrial plants, over the half of the delivered electrical energy. Motor loads specially the medium and large size ones, require high amount of reactive power for a short period during their startup. The high reactive power drawn from the system causes voltage dips at startup time...Effect of Voltage on Induction Motor Characteristics
Whenever the voltage at the terminals of an induction motor varies from its nameplate rating, either performance or life is sacrificed.The effect may be minor or serious depending upon the characteristics of the induction motor. , how it is applied and the amount of the voltage deviation from the motor rating. Standards provide...