AVy - HGB
Ch.4 56
4.4. MOTORS AND ENCODERS
The AVy Drives designed for the field oriented regulation of standard three-phase induction AC motors. A
sinusoidal encoder or digital encoder can be used for feedback in proportion to speed.
4.4.1. Motors
The electrical and mechanical data of standard three-phase motors refers to a particular operating range. The
following points should be noted when these motors are connected to an AC Drive:
Is it possible to use standard induction motors?
With the AVy Drives it is possible to use standard induction motors. Some features of the motor have a great
influence on the obtained performances. Notice also what is stated in section 3.3.4, “AC Output”, about the
voltages and the motor power.
Which properties of the asynchronous motors have an unfavorable result in operation with fre-
quency inverters?
Motors with double squirrel-cage rotors or deep rotor bars should not be used.
Star or delta connection?
Motors can be connected in both star or delta connections. Experience has shown that star connected motors
have better control properties, so star connections are preferred.
Cooling
The cooling of three-phase motors is normally implemented by means of a fan that is mounted on the motor
shaft. Remember that the output of the fan is reduced when the motor is running at lower speeds, which in
certain circumstances may mean that the cooling is insufficient for the motor. Check with the motor manu-
facturer whether an external fan is required and the motor speed range in the application concerned.
Operation above the rated speed
Due to the mechanical factors involved (bearings, unbalance of rotor) and due to the increased iron losses,
consult the manufacturer of the motor if this is operated above the rated speed .
What motor data is required for connecting the frequency inverter?
Nameplate specifications
- Motor rated voltage
- Motor rated current
- Motor rated frequency
- Motor rated speed
- Power factor
The other data required for vector control is calculated inside the inverter. In order to optimize the drive
operation it is also useful to know the values for :
- Magnetizing current
- Rotor resistance
- Stator resistance (Sensorless mode only)
- Leakage inductance ( Field oriented mode with Rotor resistance adaptation enabled or Sensorless mode.).
Motor protection
Thermistors
PTC thermistors according to DIN 44081 or 44082 fitted in the motor can be connected directly to the
frequency inverter via terminals 78 and 79. In this case the resistor (1Kohm) mounted between the terminals
78 and 79 has to be removed.
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