ENERGY SAVING DURING OPERATION OF EQUIPMENT WITH NON-CONTROLLED ELECTRIC DRIVE IN LOCOMOTIVE DEPOT

Dep. «Electric Engineering and Electromechanics», Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan, Lazaryan St., 2, Dnipro, Ukraine, 49010, tel. +38 (056) 373 15 47, ORCID 0000-0003-0319-4544 Dep. «Electric Engineering and Electromechanics», Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan, Lazaryan St., 2, Dnipro, Ukraine, 49010, tel. +38 (056) 373 15 47, ORCID 0000-0003-3602-5851 Dep. «Electric Engineering and Electromechanics», Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan, Lazaryan St., 2, Dnipro, Ukraine, 49010, tel. +38 (056) 373 15 47, e-mail baliichukaleksei@mail.ru, ORCID 0000-0003-0119-1446 Dep. «Electric Engineering and Electromechanics», Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan, Lazaryan St., 2, Dnipro, Ukraine, 49010, tel. +38 (096) 256 19 65, e-mail andrykor63@gmail.com, ORCID 0000-0001-9316-3500

Originality. For the first time the paper outlines the issues of energy saving efficiency for the equipment with noncontrolled electric drive in locomotive depot by replacing the under-loaded motors with the less powerful ones. As long as there is a significant amount of the considered electric drives, it may cause severe losses, taking into account the peculiarities of their operation. Practical value. The obtained research results allow us to solve the problem of replacement of under-loaded motors in locomotive depot equipment with the motors having less power as efficiently as possible in terms of reducing electric losses. For instance 90-kW motor of a washing machine can be replaced with 75-kW motor when the load factor is 0.7 l k ≤ , this can significantly reduce the performance losses. This method can be applied not only in locomotive depot but also for all equipment with non-controlled electric drives that operates in under-load mode.
Keywords: electric drives; locomotive depot; energy savings; active power loss; motor load factor; AIR series motors Introduction Energy saving is the strategic line of development of the main branches of the economy. A significant share of electric power consumers falls to electric motors of various purposes, which consume more than half of the energy produced [3,12]. There is where the largest energy saving reserves lie in. The repair of locomotives in a depot often involves the equipment whose electric drive motors operate in non-controlled mode. This usually includes squirrel-cage induction motors with power from tenth of kW to several tens of kW. For example, dolly, which is used for repair of locomotive bogies, has the electric motor with power of 0.8 kW; the electric motor of the assembly line for locomotive axle-box repair has power of 2.2 kW; electric motor power of the washing machine for washing the bearings is 29.7 kW, that of washing machine for washing the traction motors is 82 kW, etc. [1,16,18].

Purpose
To conduct research in order to obtain the results that will assess the degree of energy saving due to electric loss reduction in the equipment with non-controlled electric drive.

Methodology
Practice shows that in real operation conditions of this equipment, depending on the locomotive repair technology, the load factor of many electric drive motors is less than 50%. The drive operation in under-load mode results in huge losses. There are several ways to implement energy saving by means of an industrial electric drive [1,16,17,18]. In our case, the most appropriate in terms of ease of implementation and losses is the replacement of the powerful electric drive with that having less power to reduce active power losses in the motor and in the electricity network [3,4,17,18]. Let us consider the specific example, when for the purpose of equipment unification the traction motor washing machine is used for washing reduction gear housing, axle-box and other assemblies that are placed on the table of the handling dolly.
Herewith the electric drive motor load factor may vary depending on the table load.
It is necessary to analyse the reduction of active power losses in the motor and the electrical net-work when replacing the under-loaded motor mounted during the equipment manufacture with the less powerful motor when washing other (nontraction motors) units of the locomotive.
Initial data: electric drive mode is long-term. AIR series motor with the following parameters [4,9]: Motor type -5АМ250М2. The analysis is performed in accordance with [13]. We propose the following method [6,7,14]. Losses of active power in no-load mode of 5АМ250М2 motor: where 0.3 -coefficient according to [12]. Then the relative losses in no-load mode: The motor load factor: where r P -actual load of the mounted motor of the washing machine.
The feasibility of reducing the installed motor power must be justified with calculations, if: We accept: Then: The closest to 63 kW r P = and more powerful is the motor of 5AM250S4 type [3]. Specifications of 5АМ250S4 type motor: 3.98 100% 100% 5.3% 75 The total active power losses 1 P ∑ ∆ for 5AM250M2 type motor: -reactive power consumed from the network in no-load mode; where хх1 1 in1 P P ∆ γ = ∆ -design coefficient depending on the electric motor design and calculated by the formula: 2.09 kW 0.93 1 1.7 with the less powerful motor 5AM250S4 in the washing machine, we obtained the reduction of active power losses in the motor and the electricity network: ( ) , active power loss reduction in the motor and the network after replacement of the under-loaded motor with the less powerful one ranges from 0.58 kW to 2.865 kW at initial motor power of 90 kW. The obtained numerical values of reduction of these losses can be used as source information when considering the feasibility of replacement of the motors within the specified range of the load values. When using the motors with the lower synchronous speed, the effect of under-loaded motor replacement increases in terms of active power loss reduction. The greatest effect is achieved when the load factor is 0.55 l k ≤ .

Originality and practical value
For the first time the paper outlines the issues of energy saving efficiency for the equipment with non-controlled electric drive by replacing the under-loaded motors with the less powerful ones, taking into account the peculiarities of their operation in a locomotive depot.
The obtained research results allow us to solve the problem of replacement of under-loaded motors in locomotive depot equipment with the motors having less power as efficiently as possible in terms of reducing the electric losses and increasing the electric motors operation period.

Conclusions
1. The proposed method for determining the reduction of active power losses in the electric motor and the power supply network after replacing an under-loaded motor with a less powerful motor can be used during continuous mode operation of various machines at the railway rolling stock repair enterprises.
2. The obtained numerical values of reduction of these losses can be used as source information when considering the feasibility of replacement of the motors within the load factor range 0.5 0.7 l k < < . 3. When using the motors with the lower synchronous speed, the effect of under-loaded motor replacement increases in terms of active power loss reduction. The greatest effect is achieved when the load factor is 0.55 l k ≤ .