PSM 692U Motor Integrated protection, measurement and control device
1 Function
1.1 Current quick break protection
1.2 Definite time overcurrent protection
1.3 Two section definite time negative sequence overcurrent protection/inverse time negative sequence protection
1.4 Overheating protection
1.5 Locked rotor protection
1.6 Single phase grounding protection
1.7 Low voltage protection
1.8 Overload protection
1.9 Non electric quantity protection
1.10 F-C locking function
1.11 4-20mA output
1.12 9 fault recorders and 2 startup recorders
1.13 I，U，P，Q，Cos φ， Active kilowatt hour, reactive kilowatt hour, 14 circuits switch Quantity acquisition
1.14 GPS time synchronization (minute pulse, second pulse or IRIG-B mode)
2 Principle description
2.1 Current quick break protection
The current of asynchronous motor is very large during starting, usually up to 5~8 times of rated current (Ie), and the starting time can be up to tens of seconds. pretend
Two quick break settings are set, and the "starting medium speed break settings" are used in the starting process. The values are set to avoid the starting current of the motor
After the start process is completed, the "quick break fixed value after start" is automatically adopted, which is higher according to the self starting current of the motor and the short circuit at the outlet of the zone
Considering the feedback current, the larger of the two currents shall be taken.
a) The starting time tst is set to avoid a longer starting time, tst>tst.max.
b) The setting value Iop. h during startup is set by avoiding the starting current Ist of the motor, namely:
When t ≤ tst, Iop. h=krel × Ist, in order to avoid the influence of aperiodic components, krel is taken as 1.5, Ist is (6~8) Ie.
c) The setting value Iop. l during operation is set to avoid the self starting current and the large feedback short circuit of the motor in case of short circuit at the outlet of the zone. The self starting current
Size and Spare Power Supply The delay of automatic switching is related to other factors. When the fast switching of auxiliary power supply is successful, the motor almost has no self starting process, because
The speed has not decreased significantly. Only when residual voltage switching or synchronous capture switching, the motor speed has decreased significantly, and the self starting current will be larger,
According to the traditional method, the self starting current Iast=5Ie, Iop. l=krel × Iast × Ie=1.3 × 5 × Ie=6.5Ie.
The three-phase short circuit at the outlet of the zone considers the inherent delay of protection (40~60) ms, and the feedback current Ifb=6Ie.
Iop.l = krel ×Ifb=1.3×6 Ie =7.8Ie。
d) The short time delay of quick break protection is used to cooperate with F-C circuit.
