Lenze DSD - Manual (Page 434)

17 Restrictions of the drive dimensioning
17.13 Motor temperature monitoring acc. to UL 508C
434
Lenze · Drive Solution Designer · Manual · DMS 4.2 EN · 12/2013 · TD23
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
17.13 Motor temperature monitoring acc. to UL 508C
UL 508C describes special requirements for the thermal protection of motors. Carry out one of the
following measures to comply with these requirements:
• I 2 ×t motor temperature monitoring. Here, the torque must be reduced for low motor speeds
first (derating).
• Motor temperature encoder and evaluation in the inverter must be approved acc. to UL 508C.
I
2
×t motor temperature monitoring
Independent of the type of ventilation (forced ventilated, self-ventilated or naturally ventilated),
the following torque limitation must be complied with:
For f
M
= 0 Hz (standstill): M/M
rated
< 100 %
For f
M
= 20 Hz: M/M
N
= 100 %
The limitation means a derating of the motor torque. Depending on the type of ventilation of the
motor, the following derating is required:
• Self-ventilated motor
• No measures required. The available derating curves comply with the requirements.
• Forced ventilated motor
• For f
M
= 0 ... 20 Hz: Limit actual torque M
act
to 99 % M
rated
.
• Naturally ventilated motor
• For f
M
= 0 ... 20 Hz: Limit actual torque M
act
to 99 % M
rated
.
• For f
M
> 20 ... f
rated
: Limit actual torque M
act
to 100 % M
rated
.
[17-5] Torque characteristic of the motor with/without derating
 Torque characteristic of the motor in operating mode S1 (acc. to VDE 0530 or IEC 34-1)
: without derating
: with derating
M
act
/M
rated
Actual motor torque - rated motor torque ratio
f
M
Field frequency
20 f [Hz]
M
40 60 80 100
20
40
60
80
100
120
140
0
1
M
act
/M [%]
N
Œ