# Voltage regulation Question

### Help Support Professional Engineer & PE Exam Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

#### yaoyaodes

##### Well-known member
Can anyone help me out with Q21. I am not sure if I understand this correctly. On generator we can measure the terminal voltage. So when operating at full load we take 1 pu as the terminal voltage and hence we calculate internal voltage using the E0 = Ex + E formula. So at full load we have E as 1 pu. Now at no load, we will have E = E0 and E0 would still be same from the previous calculation. Only E terminal voltage keeps changing depending on the load. The internal voltage remains constant.

Hence at no load E = E0 = 1.044pu At full load we already know the generator operating at rated and hence terminal voltage will be 1 pu.

SHould the voltage regulation be (1.044-1)/1?

#### Attachments

• Screenshot 2023-09-12 202159.png
199.4 KB · Views: 1
• Screenshot 2023-09-12 202219.png
94 KB · Views: 1
• IMG_5583.jpg
465 KB · Views: 1
This question makes no sense to me.

Voltage regulation of a generator is always determined by the terminal voltage magnitude change when current goes from no load to full load with constant excitation. As far as I know, it has nothing to do with internal voltage, which remains the same magnitude under constant excitation and speed. It's a measure of the change in the terminal voltage without feedback control (AVR) for an isolated, i.e., not grid-connected, machine.

I believe changes in load always go back to the current and reactance, kind of like in the power equations (%I^2)R. So full load would be the internal voltage at 80% with the terminal voltage still at "rated" voltage 1.0pu. When you have no load, the current and reactance would be 0%, so you would only add the terminal voltage at 1.0pu.
Therefore you have 1.0pu as the "no load" and (0.8<-31.8)(0.1j)+(1.0pu) as the "full load". Thus gives you VR% = ((1.0)-(1.044))/(1.044) = -4.1%

Replies
7
Views
1K
Replies
2
Views
2K
Replies
2
Views
995