3-32
Engineering Guide CDA3000
3 Selection of inverter module
Motor protection possibilities
Fuses are not included in this comparison because they only pro-
tect the cable and not the motor.
In summary: From the point of view of “motor protection” the use of
additional motor circuit-breakers or thermistor protec-
tive relays is not required. All required safety functions
are provided by the inverter module as standard.
A B C D C+D
Overload type
Motor circuit-
breaker
(e.g. PKZM)
Thermistor
protective relay
Motor-PTC
monitoring of the
CDA3000
Software function:
motor protection
of the CDA3000
Motor-PTC moni-
toring and motor
protection of the
CDA
Overload in continu-
ous operation
1)
Heavy starting
2)
Blocking
1)
Blocking
2)
Ambient tempera-
ture >50°C
1)
Impairment of
cooling
1)
Inverter operation
<50 Hz
No protection Limited protection Full protection
1) The inverter and motor have the same power rating (1:1)
2) The inverter is at least four times larger than the motor (4:1)
3) Effective when motor warm, too long response time when motor cold
4) No full protection, because only the permissible current is applied as the basis
Table 3.23 Motor protection possibilities
3) 3)
3) 3)
4)
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