"P" - Engine start timer
"W" - Delay to emergency timer
"T" - Delay to normal timer
"U" - Engine cooldown timer
"DW" - Delay timer from open to emergency
"DT" - Delay timer from open to normal
The relays that operate the transfer switch are represented by the following letter codes: "CCE", "CCN", "CCEO" and "CCNO". The solenoids that operate the transfer switch are represented by the following letter codes: "CE", "CN", "CEO" and "CNO". The limit switches that operate the transfer switch are represented by the following letter codes: "SE" and "SN". The letter codes are used on the parts and the letter codes are used on the circuit diagrams.
The transfer of the load to the emergency power source begins automatically when any phase of the normal power source falls below the preset dropout voltage level, and the undervoltage condition is detected by the MX200 controller. The engine start timer begins. The engine start timer delay is provided in order to override outages that are only momentary. If the voltage of the normal power source returns to a value above the pickup voltage, the engine start timer cycle is reset. The transfer of power is stopped.
If the engine start timer has completed the cycle, and the voltage of the normal power source has not returned to the normal range. Then, the controller sends an engine start signal to the generator set. The microprocessor senses the voltage and the frequency of the emergency power source. When the voltage and the frequency of the emergency power source reach the preset values, the delay timer for the emergency power source begins the delay. The delay timer for the emergency power source provides a delay that is adjustable for the transfer to the emergency power source.
Once the delay to emergency timer is finished, the "CCE" relay will energize the "CE" solenoid in order to transfer the load to the emergency power source. The "SE" limit switch then activates in order to de-energize the "CCE" relay.
The transfer to the NORMAL position begins when the voltage of all phases of the normal power source have reached the pickup value.
When the normal power source is restored, the transfer to the normal power source is initiated by energizing the delay to normal timer. The delay to normal timer provides an adjustable delay in order to ensure that the normal power source has stabilized before the reconnection to the load. If the normal power source should fail before the completion of the delay timer for the normal power source, the transfer of the load to the normal power source will be stopped.
When the delay to normal timer is finished, the "CCN" relay energizes the "CN" solenoid in order to transfer the load to the normal power source. The "SN" limit switch will activate in order to de-energize the "CCN" relay. Simultaneously, the engine cooldown timer begins. The engine cooldown timer provides a period of time for the generator set to run without a load in order to cool down before shutdown.
A typical schematic of a CTS Transfer Switch is shown on illustration 1.
CTSD Models
For CTSD models, the "CCNO" relay energizes the "CNO" solenoid in order to open the ATS out of NORMAL to the OPEN position. The delay timer from OPEN to EMERGENCY begins. Once the timer has completed the cycle, the "CCE" relay energizes. The switch then completes the transfer to the emergency power source by energizing the "CE" solenoid. The "SE" limit switch activates in order to de-energize the "CCE" relay.
When the normal power source is restored, the transfer to the normal power source is initiated by energizing the delay timer for the normal power source. The delay timer for the normal power source provides an adjustable delay in order to ensure that the normal power source has stabilized before the reconnection to the load. If the normal power source should fail before the completion of the delay timer for the normal power source, the transfer of the load to the normal power source will be stopped.
When the delay to normal timer is finished, the "CCEO" relay energizes the "CEO" solenoid in order to open the ATS out of EMERGENCY to the OPEN position. The delay timer from OPEN to NORMAL begins. Once the timer has completed the cycle, the "CCN" relay energizes. The switch then completes the transfer to the emergency power source by energizing the "CN" solenoid. The "SN" limit switch activates in order to de-energize the "CCN" relay. Simultaneously, the engine cooldown timer begins. The engine cooldown timer provides a period of time for the generator set to run without a load in order to cool down before shutdown.
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| Illustration 1 | g00824014 |