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Re: CDVR Voltage regulator Per Unit Block Diagramt - Eexct_base calulation and Vp

Thank you very much Mikel!

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Re: CDVR Voltage regulator Per Unit Block Diagramt - Eexct_base calulation and Vp

The exciter time constant was on the sheet you sent me, .1881 First page, bnear bottom of block labeled "Time Constants".

 

Nominal output of a CAT PMG is 90VAC

 

MikeL.

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Re: CDVR Voltage regulator Per Unit Block Diagramt - Eexct_base calulation and Vp

Hi Mikel,

 

 

Thanks for your reply. You are right I was confused between generator and exciter filed voltage. I sent you a link to the spec file of the generator and the AVR manual in a private message.

 

From what I understand, the exciter field base voltage would be equal to the no load excitation voltage which is 10.88 V. However, I can't find Vp, the power source to the AVR, but from the AVR manual, it seems it would be between 70 and 105 V for a PM generator SR4B.

 

Finally, I'm looking for the exciter time constant Te. From the AVR manual, It's writtent that the exciter time constant Te for a PM SR4B generator is 0.22 s, Could I use this value?

 

Thank you!

 

 

Super Contributor

Re: CDVR Voltage regulator Per Unit Block Diagramt - Eexct_base calulation and Vp

How about providing your serial number or a copy of the spec sheet you're working from.

 

The CDVR is a broad range voltage regulator, works on lots of different generators, both Cat and others.

 

You values should come from the generator technical info, not from the voltage regulator information.

 

MikeL.

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Accepted Solution

CDVR Voltage regulator Per Unit Block Diagramt - Eexct_base calulation and Vp

Hi,

 

I'm having trouble finding Vp (power input voltage) and Eef_base (nominal exciter field voltage at no load).

 

I have caterpillar generator SR4B, permanent magnet and an CDVR voltage regulator. From page 33 of the AVR manual, I guess Vp would be between 70 to 105 (column Input to regulator). Then, for Eef_base, would it be 35 V (coloum Exciter Nominal Voltage Input)?

 

However, I'm confused with the generator spec sheet. It says that the field resistance is 1.522 ohm (in AVR manual, it says exciter resistance 3.7 ohms). From the Air Gap curve, I find that the field current to have nominal voltage at generator output is 22.8 Amps (in AVR manual, it says exciter nominal current input is 10 A). From the generator spect, I would calculate Eef_base=1.522*22.8A=34.7 V.

 

From the AVR manual page 6, the minimum exciter field resistance is 3 ohm which is higher the field resistance of the generator (1.522 ohms). Is it necessary to add a series resistance?

 

From the generator spec sheet. I have at no load and Excitation voltage of 10.88 V and excitation current of 3.4 Amps. At full load, the excitation voltage is 41.08 Voltage and excitation current of 3.4 Amps. Are these values relevant to calculate Eef_base?

 

How am I supposed to find Vp and Eexct_base.

 

Thank you for your help!