What are the calculations needed to determine the armature current and speed of a DE series motor?
The calculations needed to determine the armature current and speed of a DE series motor are as follows:
1. Calculate the input power at full load which is equal to the output power (300 hp or 223.7 kW).
2. Use the input power and voltage (400 V) to find the armature current (Ia).
3. Calculate the torque (T) using the motor constant (Ka), armature current (Ia), flux per pole (Φ), and armature resistance (Ra).
4. Add the rotational losses to find the total torque.
5. Use the total torque and other parameters to calculate the speed of the motor in rpm.
Let's break down each calculation in detail:
Calculation of Input Power:
Input Power = Output Power = 300 hp = 223.7 kW
At full load, the input power is equal to the output power, so the input power is 300 hp or 223.7 kW.
Calculation of Armature Current (Ia):
Ia = Input Power / Voltage = 223.7 kW / 400 V = 559.25 A
We can calculate the armature current by dividing the input power by the voltage.
Calculation of Torque (T):
T = (Ka × Ia × Φ) / (N - IaRa) + Rotational Losses
- Ka is the motor constant (0.012/2 s/rad)
- Φ is the flux per pole in Wb
- N is the speed of the motor in rpm
- Ra is the armature resistance
Calculation of Speed:
N = 500,000 / Ia = 500,000 / 559.25 = 894.15 rpm
We can determine the speed of the motor by dividing 500,000 by the armature current.
In conclusion, by following the calculations above, we can determine the armature current and speed of a DE series motor at full load. These calculations are essential for understanding the performance and efficiency of the motor in real-world applications.