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Frequently Asked Question
Topic:
How can Inverter Efficiency be calculated?
Author
Yaskawa
Product:
All
Date
22-Jun-2010
Keywords:
Efficiency, power loss
Pages
1 of 2
Distribution:
Internal Use only
Customer
Equations:
In general, efficiency is given by the following formula:
Efficiency = Pout / Pin x 100%
(eq. 1)
Input power can be written as a function of output power.
Pin = Pout + losses
(eq. 2)
Substituting eq. 2 into eq. 1, we obtain:
Efficiency = Pout / (Pout + losses) x 100%
(eq. 3)
Output power is calculated as follows:
Pout = √3 x Vout x Iout x PFmotor
´
(eq. 4)
Where PFmotor is assumed to be 0.85
Example:
Calculate the efficiency for a A1000 running at full load and rated speed.
Step 1: Look up heat loss data
Referencing the heat loss chart in the A1000 Technical Manual, we see that for a CIMRAC4A0031 the total losses are 455.2W for ND mode and 2 kHz carrier frequency, as
well as 323.2W for HD mode and 8 kHz carrier frequency.
How can Inverter Efficiency be calculated.doc
Seite 2 von 2
22.06.2010
Step 2: Calculate output power
Rated current for a CIMR-A0031 is 31A for ND mode. From eq. 4:
Pout = √3 x 400V x 31A x 0.85
= 18,255 kW
Rated current for a CIMR-A0031 is 24A for HD mode. From eq. 4:
Pout = √3 x 400V x 24A x 0.85
= 14,133 kW
Step 3: Calculate efficiency
Using eq. 3:
Efficiency for ND mode
=18,255kW / (18,255kW + 455,2W) x 100%
= 97.6% (For ND mode)
Efficiency for HD mode
=14,133kW / (14,133kW + 323,2W) x 100%
= 97.6% (For HD mode)
In case more detailed information about heat losses (different output currents, different
carrier frequencies) are required please contact your local sales contact.
How can Inverter Efficiency be calculated.doc