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Technical specifications

Download ⇒ the complete file "Technical specifications" .

1. General

The prerequisite for the perfect operation of a drive is the correct selection of the motor. Here it is important to know the torque required to drive a piece of machinery. Both overloading and too low loading can have unwanted consequences. It is therefore advisable to take into account the following explanations concerning the properties of the different types of motor as well as the electrical and mechanical designs. The expert assistance of our engineers is available to our customers to simplify the selection. Furthermore, measurements required for optimizing a drive can be performed in our laboratory.

2. Characteristics of the different types of motor

2.1 Commutatormotors

can be wound for voltages up to 250 V with speeds up to approx. 25,000 rpm. At higher speeds, wear, noise and power loss increase and increases in power are not possible for thermal reasons. Values are placed in brackets for this in the catalogue. Speeds below 3,000 rpm are also not expedient for series motors, because the efficiency becomes bad and the speed response very unstable. At low operating voltages, it must be examined whether the win- ding can be produced at all and whether sufficient brush cross-sections are available. (Reference to radio interference see item 4.6.).

2.1.1 Series wound motors (Universal motors)

(Circuit diagram groups S 01- to S 07-)

also called universal motor, can be connected both to alternating and to direct voltage. Their power at low speed is more on direct voltage than on alternating voltage (at 3,000 rpm approx. 100 %). The difference becomes smaller with increasing speed; above 8,000 rpm the operating behaviour is almost the same on both types of voltage. Motors with low speed can be equipped with a tapped winding for optional connection to direct or alternating voltage at the same power. One advantage of series motors is their large starting torque, a disadvantage is their high speed dependence when the load torque changes. Series motors should therefore not be selected with a power reserve, for the unused extra power results in a (frequently unwanted) increase in speed. Diverter Potentiometer control (circuit diagram group KS 01-) is suitable for continuously variable speed control. In the case of split field reversing (circuit diagram groups S 02- and S 03-) only approx. 70 % of the power stated in the catalogue can be obtained.

2.1.2 Shunt wound motors

(Circuit diagram group S 09-)

can be connected basically only to direct voltage. If only alternating voltage is available, this can be converted into the required direct voltage, for instance with the aid of rectifiers. In the case of current with a strong ripple, a choke coil should be connected in the armature circuit. The main advantage of Shunt motors is their „speed rigidity", i.e. speed changes only significantly when the load fluctuates. However, it can be adjusted within wide limits by changing the armature voltage but keeping the field excitation constant. Speed adjustment by changing the field excitation
is not recommended for small motors. The field windings are designed so that even with the motor at standstill (armature voltage = zero), the excitation can be switched on arbitrarily long.

2.1.3 Permanent magnet motors

(Circuit diagram group S 21-)


behave in a manner similar to Shunt motors, but have a considerably higher starting torque. In addition, no excitation power is required forthese motors (important for battery operation).

2.1.4 Compound wound motors

(Circuit diagram group S 12-)

largely unite the advantages of series and Shunt motors. Load changes have less effect on the speed than in the case of series motors. The starting torque is larger than for Shunt motors and the starting properties are more favourable - e.g. lower sparking onswitching on. Compound motors can also only be operated on direct voltage. In the case of rectified Compound motors, the series winding also acts as choke coil and contributes somewhat to reducing the ripple of the armature current. Commutation is improved by this.

2.2 Squirell-cage-motors

 

2.2.1 Asynchronous motors

are built for 3- or 1-phase alternating voltage up to 500 V (for smaller types up to and including size 70 only up to 380 V) in 2- and 4-pole version; higher numbers of poles are also possible from type size 80 onwards. The speed depends upon the iine frequency and the number of poles of the motor. In generai. asynchronous motors have an almost fixed speed like Shunt motors and have the following advantages compared with commutator motors: quiet running (no brush noise), no parts subject to wear (the ball bearings have very long life) and no radio interference.

2.2.1.1 Three phase motors


(Circuit diagram group S 61-)

are generally viewed as the ideal drive motors for fixed speeds and are preferred whenever a 3-phase power supply is available. They have a good efficiency (and thus favourable power-to-weight ratio) and according to type size a starting torque up to 300 % of the nominal torque. They are sturdy and can be overloaded briefly. Our three-phase motors can be switched on directly like all our squirrel-cage motors. They require neither starters nor other starting aids.

2.2.1.2 AC capacitor motors

(Circuit diagram groups S 56-, S 58-)

have in general a 2-strand winding and are operated on single-phase alternating voltage by means of operating capacitor. They are designed optimally for one operating point; at no-load, noise and heating are higher. Compared with three-phase motors, they have a considerably lower starting torque (30 to 60 % of the nominal torque) and lower power for the same type size. The starting torque can be increased by special rotors at the expense of power and speed. A significant increase in starting torque can be achieved while retaining maximum power of the motor by a starting capacitor. This is shut down after the run-up, for instance with auxiliary starting switch manually or auxiliary starting relay by the current. Furthermore, three-phase motors can be connected with operating capacitors in Steinmetz connection to single-phase alternating current (circuit diagram S61-0301-54). They behave like 2-strand capacitor motors, require around twice the capacitor capacitance and deliver only 70 - 80 % of the three-phase power.

2.2.1.3 Pole-changing motors

(Circuit diagram group S 63-)

are usually three-phase motors with a special winding which can be switched over in the speed ratio of 2:1 (e.g. 2,800/1,400 rpm, from type size 80 onwards also 1,400/700 rpm). Speed ratios of 3:1 or 4:1 can also be obtained by separate windings. Pole-changing motors can also be connected to single-phase alternating voltage by means of operating capacitor. The powers of the pole-changing motors are more or less reduced compared with the cataiogue data.

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Download  ⇒ the complete file "Technical specifications" and read more further informations about:

  • Special designs
    • Tachogenerators
  • Electrical specifications 
    • VDE regulations
    • Foreign standards
    • Voltage- frequency- power heating
    • Insulation
    • EMC Directive
  • Mechanical design
    • Structural shapes
    • Run-out-tolerances
    • Protection classes
    • Bearings and lubrication
    • Radial and axial load of the drive shaft
  • Breaks
    • Gearmotors

and much more

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