ABB UNITROL 1020 - Page 95

 Chapter 5 - Commissioning
UNITROL 1020 User Manual 3BHS335648 E82 87
PWM no load: Regulator output at no load (PWM)
Definition: The ceiling factor Kceil determines the relationship between the maximum
output voltage of the regulator and the exciter voltage, which is required for no-load
excitation and is thus a measure for the possible overexcitation of the machine.
Example: Regulator output signal (PWM) at no load shows 20% at nominal voltage
20
100

ceil
K
= 5
Calculating method
Power electronics supply
Three-phase
Uemax = 1.35 * UPWR - 8 V
Single-phase
Uemax = 1.25 * UPWR - 8 V
DC
Uemax = 0.98 * UPWR - 8 V
Example
Specifications
Power electronics supply U
PWR
= 240 V, single-phase
No-load exciter voltage Ueo = 50 V
Calculation
Uemax = 1.25 * 240 V - 8 V = 292 V
Kceil = 292 V/50 V = 5.8 p.u.
NOTICE!
The Kceiling value must be in the range of 5 to 15 in order to
achieve optimal and stable regulation. If not, the input voltage
value may have to be reduced.
NOTICE!
The ceiling value must be calculated for a machine working at
nominal load, therefore ceiling factor measurement with PWM can
only be considered after the machine reaches nominal operational
temperature.
5.3.1.2 Setup \ System Data, Machine Reactance Xq (non-saturated)
- Salient pole machine: Xq ≈ 0.7 to 0.5 Xd
- Cylindrical-rotor machine (Turbo): Xq ≈ Xd