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| Illustration 1 | g00888249 |
Typical Block Diagram of SR4B HV Generator with K65-12B Voltage Regulator (1) Generator lines (output voltage) (2) Generator lines (sensing voltage and AC power) (3) K65-12B voltage regulator (4) Jumper (5) Main stator (6) Main rotor (7) Exciter rotor (8) Exciter stator (9) Three-phase full wave rectifiers (10) Permanent magnet stator (11) Permanent magnet (12) Generator lines (DC excitation voltage) | |
This manual covers the K65-12B voltage regulator which is used on SR4B 2600 Frame generators. The K65-12B regulator is typically located in the switchgear or the regulator is typically located in a remote generator set control panel.
The K65-12B voltage regulator (3) keeps the generator output voltage constant with changing loads. The voltage regulator controls the DC voltage and current that is supplied to the exciter stator (8).
The regulator senses the generator voltage through the generator sensing leads (2). The sensing leads are connected to the following terminals: 20, 22 and 24. The sensed voltage is then compared to a reference voltage. The value of the reference voltage is set by the voltage adjust rheostat on the regulator. The value of the reference voltage may also be set by an external voltage adjust rheostat.
When the regulator senses a decrease in output voltage due to an increase in load, the regulator will increase the DC voltage on wires F1 and F2 (12). This increases the magnetic field in the exciter stator (8). The increased magnetic field in the exciter stator increases the AC voltage and current, which is induced in the exciter rotor (7). This increased three-phase AC voltage from the exciter rotor causes more AC current to flow. The three-phase AC voltage is then rectified to DCV by the three-phase full wave rectifier (9). The increased DC output from the bridge rectifier is carried to the main rotor (6) by conductors, which are routed through a passage in the generator shaft. Increased current through the main rotor increases the magnetic field of the generator. The increased magnetic field induces a larger AC voltage into the main stator (5). Therefore, the three-phase AC voltage (1) increases until the voltage regulator no longer senses a decreased output voltage.
When the voltage regulator senses an increase in output voltage due to a decrease in load, the regulator will decrease the DC voltage to the exciter. A decrease in generator voltage will occur due to similar responses, as described above.
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| Illustration 2 | g00779058 |
The K65-12B Voltage Regulator (13) Terminal strip for attachments (14) Droop adjustment (15) Factory calibration of the voltage adjustment range (16) Voltage adjustment (17) Knee frequency adjustment (18) Stability adjustment (19) Terminal strip for sensing and power | |
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| Illustration 3 | g01021519 |
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The Cat K65-12B Voltage Regulator presents an electrical shock/electrocution hazard. This hazard will cause serious injury or death. Service by trained personnel only. The terminals and heat sinks are live at hazardous voltages when power is applied and for up to 8 minutes after power is removed. |
There are five adjustments on the K65-12B voltage regulator:
- Droop adjustment (14)
- Factory calibration of the voltage adjustment range (15)
- Voltage adjustment (16)
- Knee frequency adjustment (17)
- Stability adjustment (18)
The factory calibration of the voltage adjustment range (15) should not be adjusted by the user. For the other adjustments, refer to the Testing and Adjusting Section within this manual.
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| Illustration 4 | g01021519 |
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The Cat K65-12B Voltage Regulator presents an electrical shock/electrocution hazard. This hazard will cause serious injury or death. Service by trained personnel only. The terminals and heat sinks are live at hazardous voltages when power is applied and for up to 8 minutes after power is removed. |
The excitation circuit can be disabled by removing the power from the K65-12B.
The K65-12B voltage regulator can operate in one of the following modes:
- three-phase sensing
- single-phase sensing
For three-phase sensing, place the jumper between terminals 6a and 9. Sensing leads (2) should be connected to terminals 20, 22 and 24 for three-phase sensing.
For single-phase sensing, the jumper should be removed. Sensing leads (2) should be connected to terminals 20 and 22 for single-phase sensing.
Note: The K65-12B voltage regulators are sensitive to A-B-C phase rotation. Connections should be "T1" to 22, "T2" to 24 and "T3" to 20. Incorrect connections can result in high circulating currents during parallel operation.
Note: Rated sensing voltage for the K65-12B is 120 ACV for 50 Hz systems and 60 Hz systems. The sensing voltage can be adjusted +10% or -25%. The generator has a much higher operating voltage. Potential transformers (PT) must be used in order to step down the output voltage to 120 ACV.
The leads from permanent magnet (11) are connected to terminals 26, 28 and 30 on the voltage regulator. These leads provide power to the regulator. Terminals 26, 28, and 30 are part of the terminal strip for sensing and power (19). There is a jumper between terminals 28 and "GND".
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| Illustration 5 | g01021519 |
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The Cat K65-12B Voltage Regulator presents an electrical shock/electrocution hazard. This hazard will cause serious injury or death. Service by trained personnel only. The terminals and heat sinks are live at hazardous voltages when power is applied and for up to 8 minutes after power is removed. |
The terminal strip for attachments (13) accommodates the following optional connections:
- KVAR/PF controller
- Min/Max excitation limiter
- External voltage adjust rheostat
- Droop current transformer (CT)
- Selection of the underfrequency slope
- Selection of the sensing phase
The KVAR/PF controller and/or the min/max excitation limiter is connected at terminals 2 and 3. Terminals 2 and 3 should be jumpered if the KVAR/PF controller is not used.
If an external voltage adjust rheostat is used, there should be no jumper between terminals 4 and 7. An external voltage adjust rheostat is rated at 10 kOhm and 2 Watt. An external voltage adjust rheostat is connected between terminals 6a and 7. If the internal voltage adjust rheostat is used, place the jumper between terminals 4 and 7.
If a 1 Ampere droop current transformer (CT) is used, the CT secondary should be connected between terminals 5 and 6. If a 5 Ampere droop current transformer (CT) is used, the CT secondary should be connected between terminals 5a and 6.
In order to create a 1 V/Hz underfrequency slope, place the jumper between terminals 6a and 8. Leave these terminals unconnected for a 2 V/Hz underfrequency slope.
Connect terminal 6a to terminal 9 for three-phase sensing. Do not connect these terminals for single-phase sensing.