7

Aeroflex Circuit Technology

SCD5101-1 REV D 5/14/01 Plainview NY (516) 694-6700

FIGURE 4 - IGBT COLLECTOR-TO-EMITTER VOLTAGE VS. COLLECTOR CURRENT

Based upon this voltage drop and the conduction duty cycle a conduction power loss may be calculated

as:

where:

Conduction IGBT Power Dissipation

Switch Duty Cycle, (.33 for brushless drives in run condition, 1 in stall)

PWM on/off ratio

Collector Emitter voltage from Figure 4 for a particular collector current

Collector current

Switching losses are dependent upon the operating frequency, collector current and again duty cycle as:

where:

Switching IGBT Power Dissipation

Turn on energy loss from Table 2

Turn off energy loss from Table 2

Pulse width modulation frequency

Collector current

Commutation diode losses are calculated as:

80

70

60

50

40

30

20

10

1.6

1.4

1.2

1.0

2.4

2.2

2.0

1.8

2.8

2.6

(V)

T

P

c

δ

S

δ

PWM

V

CE

I

C

⋅⋅

⋅

=

P

s

δ

S

E

on

E

off

+

[] f

o

I

C

40

------

⋅⋅ ⋅

=

P

d

δ

s

1

δ

PWM

–

[] V

f

I

f

⋅⋅

⋅

=