SIM6800M datasheet(28/52 Pages) SANKEN

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SIM6800M Series

SIM6800M-DSE Rev.1.5

SANKEN ELECTRIC CO., LTD

Jul. 18, 2018

http://www.sanken-ele.co.jp/en

14. Calculating Power Losses and

Estimating Junction Temperatures

This section describes the procedures to calculate

power losses in switching transistors, and to estimate a

junction temperature. Note that the descriptions listed

here are applicable to the SIM6800M series, which is

controlled by a 3-phase sine-wave PWM driving

strategy.

For quick and easy references, we offer calculation

support tools online. Please visit our website to find out

more.

● DT0026: SIM682xM Calculation Tool

http://www.semicon.sanken-ele.co.jp/en/calc-

tool/sim682xm_caltool_en.html

● DT0027: SIM681xM Calculation Tool

http://www.semicon.sanken-ele.co.jp/en/calc-

tool/sim681xm_caltool_en.html

● DT0030: SIM688xM Calculation Tool

http://www.semicon.sanken-ele.co.jp/en/calc-

tool/sim688xm_caltool_en.html

14.1 IGBT

Total power loss in an IGBT can be obtained by

taking the sum of steady-state loss, PON, and switching

loss, PSW. The following subsections contain the

mathematical procedures to calculate these losses (PON

and PSW) and the junction temperature of all IGBTs

operating.

14.1.1

IGBT Steady-state Loss, PON

Steady-state loss in an IGBT can be computed by

using the VCE(SAT) vs. IC curves, listed in Section 15.3.1.

As expressed by the curves in Figure 14-1, linear

approximations at a range the IC is actually used are

obtained by: VCE(SAT)

= α × I

+ β. The values gained by

the above calculation are then applied as parameters in

Equation (4), below. Hence, the equation to obtain the

IGBT steady-state loss, PON, is:

PON= 12π�VCE(SAT)(φ)×IC(φ)×DT×dφ

=12α�12+43πM×cosθ�IM2

+√2πβ�12+π8M×cosθ�IM. (4)

Where:

VCE(SAT) is the collector-to-emitter saturation voltage of

the IGBT (V),

IC is the collector current of the IGBT (A),

DT is the duty cycle, which is given by

DT=1+M×sin(φ+θ)

2 ,

M is the modulation index (0 to 1),

cosθ is the motor power factor (0 to 1),

IM is the effective motor current (A),

α is the slope of the linear approximation in the

VCE(SAT) vs. IC curve, and

β is the intercept of the linear approximation in the

VCE(SAT) vs. IC curve.

Figure 14-1.

Linear Approximate Equation of

VCE(SAT) vs. IC Curve

14.1.2

IGBT Switching Loss, PSW

Switching loss in an IGBT can be calculated by

Equation (5), letting IM be the effective current value of

the motor:

PSW=√2π×fC×αE×IM×VDC300.

(5)

Where:

fC is the PWM carrier frequency (Hz),

VDC is the main power supply voltage (V), i.e., the

VBB pin input voltage, and

E is the slope of the switching loss curve (see Section

15.3.2).

14.1.3

Estimating Junction Temperature

of IGBT

The junction temperature of all IGBTs operating, Tj,

can be estimated with Equation (6):

Tj=R(j−C)Q×{(PON+PSW)×6}+TC. (6)

Where:

R(j-C)Q is the junction-to-case thermal resistance

(°C/W) of all the IGBTs operating, and

TC is the case temperature (°C), measured at the point

y = 0.2051x + 0.8859

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0.0

1.0

2.0

3.0

4.0

5.0

C (A)

VCC = 15 V

°C

125

°C

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