【单选题】
步进电动机在高频区工作产生失步的原因是___。
A. 励磁电流过大
B. 励磁回路中的时间常数(T=L/R)过小
C. 输出转矩随频率f的增加而升高
D. 输出转矩随频率f的增加而下降
查看试卷，进入试卷练习
微信扫一扫，开始刷题
答案
D
解析
暂无解析
相关试题
【单选题】
双闭环调速系统中电流环的输入信号有两个，即___。
A. 主电路反馈的转速信号及ASR的输出信号
B. 主电路反馈的电流信号及ASR的输出信号
C. 主电路反馈的电压信号及ASR的输出信号
D. 电流给定信号及ASR的输出信号
【单选题】
直流双闭环调速系统引入转速微分负反馈后，可增强调速系统的抗干扰性能，使负载扰动下的___大大减小，但系统恢复时间有所延长。
A. 静态转速降
B. 动态转速降
C. 电枢电压超调
D. 电枢电流超调
【单选题】
626，直流双闭环调速系统引入转速微分负反馈后，可使突加给定电压启动时转速调节器提早退出饱和，从而有效地___
A. 抑制转速超调
B. 抑制电枢电流超调
C. 抑制电枢电压超调
D. 抵消突加给定电压突变
【单选题】
转速电流双闭环调速系统稳态时，转速n与速度给定电压Ugn速度反馈a之间的关系是：___。
A. n≠Ugn/α
B. n≥Ugn/aα
C. n=Ugn/α
D. n≤Ugn/α
【单选题】
双闭环直流调速系统启动时，速度给定电位器应从零开始缓加电压，主要目的是___。
A. 防止速度调节器ASR启动时饱和
B. 保护晶闸管，防止过电压
C. 保护品闸管和电动机
D. 防止电流调节器ACR启动时限幅
【单选题】
带转速微分负反馈的直流双闭环调速系统的动态转速大大降低，RdnCdn值越大，___。
A. 静态转速降越低，恢复时间越长
B. 动态转速降越低，恢复时间越长
C. 静态转速降越低，恢复时间越短
D. 动态转速降越低，恢复时间越短
【单选题】
对恒转矩负载，交流调压调速系统要获得实际应用，必须具备的两个条件是采用___。
A. 低转子电阻电机且闭环控制
B. 高转子电阻电机且闭环控制
C. 高转子电阻电机且开环控制
D. 绕线转子电机且闭环控制
【单选题】
在闭环控制交流调压调速系统中，负载变化范围受限于___时的机械特性，超出此范围闭环系统便失去控制能力。
A. 电压为U1nom
B. 电压为U1min
C. 电压为U1mon与U1min
D. 电压为1.2U1mon
【单选题】
变频器常见的频率给定方式主要有：模拟信号给定、操作器键盘给定、控制输入端给定及通信方式给定等，在PLC控制系统时不采用___方式。
A. 键盘给定
B. 控制输入端给定
C. 模拟信号给定
D. 通信方式给定
【单选题】
恒功率负载变频调速的主要问题是如何减小传动系统的容量。常见的恒功率负载有___。
A. 起重机、车床
B. 带式输送机、车床
C. 带式输送机、起重机
D. 薄膜卷取机、车床
【单选题】
无论采用的交一直一交变频器是电压型还是电流型，控制部分在结构上均由___三部分组成。
A. 电压控制、频率控制以及两者协调控制
B. 电压控制、电流控制以及两者协调控制
C. 电压控制、频率控制以及电流控制
D. 电流控制、频率控制以及两者协调控制
【单选题】
根据生产机械调速特性要求的不同，可采用不同的变频调速系统。采用___的变频调速系统技术性能最优。
A. 开环恒压频比控制
B. 无测速矢量控制
C. 有测速矢量控制
D. 直接转矩控制
【单选题】
测速发电机的灵敏度高，对调速系统性能的影响是___。
A. 没有影响
B. 有影响，灵敏度越高越好
C. 有影响，灵敏度越低越好
D. 对系统的稳态性能没有影响，但对动态性能有影响
【单选题】
___就是在原有的系统中，有目的地增添一些装置(或元件)，人为地改变系统的结构和参数，使系统的性能获得改善，以满足所要求的稳定性指标。
A. 系统校正
B. 反馈校正
C. 顺馈补偿
D. 串联校正
【单选题】
在带PI调节器的无静差直流调速系统中，可以用___来抑制突加给定电压时的电流冲击，以保证系统有较大的比例系数来满足稳态性能指标要求。
A. 电流截止正反馈
B. 电流截止负反馈
C. 电流正反馈补偿
D. 电流负反馈
【单选题】
与通用型异步电动机相比变频调速专用电动机的特点是___。
A. 外加变频电源风扇实行强制通风散热；加大电磁负荷的裕量；加强绝缘
B. U/f控制时磁路容易饱和；加强绝缘；外加电源变频风扇实行强制通风
C. 外加电源变频风扇实行强制通风；加大电磁负荷的裕量；加强绝缘
D. 外加工频电源风扇实行强制通风；加大电磁负荷的裕量；加强绝缘
【单选题】
测速发电机的用途广泛，可作为___。
A. 检测速度的元件，微分、积分元件
B. 微分、积分元件，功率放大元件
C. 加速或延迟信号，执行元件
D. 检查速度的元件，执行元件
【单选题】
控制系统对直流测速发电机的要求有___。
A. 输出电压与转速成线性关系，正反转特性一致
B. 输出灵敏度低，输出电压纹波小
C. 发电机的惯性大，输出灵敏度高
D. 输出电压与转速成线性关系，发电机的惯性大
【单选题】
国产CYD系列高灵敏直流测速发电机，具有结构简单、耦合度好、___、反应快、可靠性好的特点。
A. 输出比电势低，线性误差小
B. 输出比电势高，线性误差小
C. 输出比电势高，线性误差大
D. 输出比电势低，线性误差大
推荐试题
【单选题】
Which statement is true regarding the use of VMFS3 datastores with vSphere 6.5?___
A. VMFS3 datastores can be used but not created.
B. VMFS3 datastores can be neither used nor created.
C. VMFS3 datastores will be present but unmounted.
D. VMFS3 datastores can be created and used.
【单选题】
In the Exhibit, each VM has a 1GHz non-expandable reservation. If all VMs are powered on in sequence, what would be the outcome?___
A. VM4 cannot be powered on.
B. VM5 cannot be powered on.
C. VM6 cannot be powered on.
D. VM3 cannot be powered on.
【单选题】
vSphere 6.5 introduced MAClearning capabilities for VMware’s virtual switches. What three benefits will it provide? (Choose three.)___
A. Reduced memory consumption.
B. Reduced consumption of extra CPU cycles.
C. Increased network throughput.
D. Prevent packet flooding inside the vSwitch.
【单选题】
What is the default pathing policy for most active-active arrays?___
A. Fixed
B. Most Recently Used
C. Dynamic
D. isk Morroring
【单选题】
Which command will show the iSCSI sessions on a ESXi 6.5 host?___
A. esxcli storage iscsi session get
B. esxcli iscsi session get
C. esxcli storage iscsi session
D. esxcli iscsi session list
【单选题】
Which of the following is not a parameter for traffic filtering or marking?___
A. virtual port ID
B. Protocol
C. Traffic Direction
D. DSCP value
E. Traffic redirection
【单选题】
A vSphere administrator wants to enable a virtual machine with Secure Boot, but in VM setting, Secure Boot option was not found under Boot Options. What could be the cause?___
A. The virtual hardware is not compatible.
B. The virtual machine has missing drivers.
C. The virtual machine OS does not support secure boot.
D. VMware Tools is not upgraded.
【单选题】
A virtual machine is connected on a distributed port group where the average bandwidth configured in the traffic shaping policy is 100 Mbps. The VM network adapter is configured with a reservation of 200 Mbps. What is the VM’s effective bandwidth?___
A. 200 Mbps
B. 100 Mbps
C. 150 Mbps
D. 400 Mbps
【多选题】
What are two reasons why a datastore in a Storage DRS cluster cannot enter maintenance mode?(Choose two.)___
A. Storage latency is too high to allow Storage DRS initiate Storage vMotion.
B. Storage DRS is configured for a VMFS3 datastore.
C. Storage
D. RS is disabled on the virtual disk.
【多选题】
What two methods are used to configure VMware vSphere Storage I/O Control shares and limits? (Choose two.)___
A. Assign shares and limits to VM virtual disks.
B. Assign shares and limits to datastores.
C. Assign shares and limits to Storage (DRS) clusters.
D. Assign shares and limits using VM storage policies.
【多选题】
ESXi 6.5 introduces VMFS6, which supports both 512e and 512n devices. What three configurations are supported when using these devices? (Choose three.) ___
A. Hosts with both 512e and 512n devices.
B. Storage vMotion between both 512e and 512n devices.
C. Datastore Extents spanned between both 512e and 512n devices.
D. Storage DRS clusters containing only both 512e and 512n devices.
【多选题】
A vSphere Administrator observes that the Primary VM configured with Fault Tolerance is executing slowly. After further investigation, it is determined that the Secondary VM is on an overcommitted ESXi host. What two methods will correct the problem? (Choose two.)___
A. Use Storage vMotion to migrate the Secondary VM to another datastore.
B. Use vMotion to migrate the Secondary VM to a different ESXi host.
C. Configure a CPU limit on the Primary VM which will also apply to the Secondary VM.
D. Turn off and turn on FT in order to recreate the Secondary VM on a different datastore.
【多选题】
Which two features require the use of Host Profiles? (Choose two.)___
A. Host Customizations
B. shared storage
C. Auto
D. eploy
【多选题】
What three processes on the vCenter Server Appliance (VCSA) does“vmware-watchdog monitor? (Choose three.) ___
A. vmware-eam
B. vmcad
C. vmware-vpostgres
D. vpxd
E. vsan-health
【多选题】
What three processes on the vCenter Server Appliance (VCSA) does“vmware-watchdog monitor? (Choose three.) ___
A. vmware-eam
B. vmcad
C. vmware-vpostgres
D. vpxd
E. vsan-health
【多选题】
Which two statements correctly describe VM-Host affinity rules? (Choose two.) ___
A. When there is more than one VM-Host affinity rule in a vSphere DRS cluster, the rules are applied equally.
B. After creating a VM-Host affinity rule, its ability to function in relation to other rules is predetermined.
C. When there is more than one VM-Host affinity rule in a vSphere
D. RS cluster, the rules will be ranked.
【多选题】
An administrator wants to enable proactive HA by moving virtual machines automatically if a hardware alert is triggered. What are the three required settings? (Choose three.)___
A. Set vSphere DRS Automation to Partially Automated.
B. Turn on Proactive HA.
C. Set the Proactive HA Automation Level to Manual.
D. Set the Proactive HA Automation Level to Automated.
E. Turn on vSphere HA and vSphere DRS.
【多选题】
If vCenter Server 5.5 installation has one or more services deployed remotely, which three services are relocated to vCenter Server 6.5 on upgrade? (Choose three.)___
A. vCenter Inventory Services
B. vSphere Authentication Proxy
C. vSphere Web Client
D. vSphere
E. SXi Dump Collector
【多选题】
What two debugging levels can a virtual machine be configured to? (Choose two.)___
A. Verbose
B. Debugging
C. Statistics
D. Trivia
【多选题】
What are three benefits of using a few large-capacity LUNs instead of many small-capacity LUNs? (Choose three.) ___
A. Better performance because there is less contention for a single volume.
B. More flexibility for resizing virtual disks.
C. Less wasted storage space.
D. More flexibility to create virtual machines without adding new LUNs.
E. Fewer VMFS datastores to manage.
【多选题】
Which two configurable options are available in Boot Options for a virtual machine? (Choose two.)___
A. Tools Upgrades
B. Encryption
C. Firmware
D. Force BIOS setup
【多选题】
Which three VMware-recommended best practices should an administrator follow before upgrading to vSphere 6.5? (Choose three.)___
A. Disconnect ESXi host from vCenter.
B. VMware Tools are installed in the virtual machine.
C. Ensure that the system hardware complies with ESXi requirements.
D. Back up the host.
E. Check the interoperability of any other software integrated with vSphere.
【多选题】
What are two requirements to enable EVC in vSphere DRS cluster? (Choose two.)___
A. CPUs must be from the same vendor.
B. EVC must use the lowest possible baseline supported by the hardware.
C. CPUs must be in the same family and of the same speed.
D. No VMs may be running in the cluster.
【多选题】
What three conditions could result in VMware Flash Read Cache being unable to claim a disk? (Choose three.)___
A. The disk is not listed in the VMware hardware compatibility guide.
B. The disk is not detected as an SSD.
C. The disk is not detected as local.
D. The disk is in use by VMFs.
【多选题】
Boot from SAN is supported on which three storage technologies? (Choose three.)___
A. VMware vSAN
B. FCoE
C. NFS 4.1
D. iSCSI
E. FC
【多选题】
Which two components are part of storage I/O multipathing on ESXi? (Choose two.)___
A. SATP
B. VASA
C. PSP
D. VAAI
【多选题】
Which two statements are true about Highly Available vSphere Auto Deploy infrastructure? (Choose two.)___
A. It helps prevent data loss.
B. It is a prerequisite for using vSphere Auto Deploy with stateful install.
C. It requires two or more Auto
D. eploy servers.
【多选题】
The virtual machine log rotation size can be changed for all VMs by which two interfaces? (Choose two.)___
A. PowerCLI
B. vSphere Web Client
C. ESXi host client
D. esxcli
【多选题】
Which two configuration options can exclude virtual disks from snapshot operations? (Choose two.)___
A. Use RDM in virtual mode for virtual disk.
B. Use virtual disks in Independent – Persistent mode.
C. Use a virtual disk larger than 2 TB in size.
D. Use RDM in physical mode for virtual disk.
【多选题】
Which two storage configurations on the source server are unsupported with VMware Converter? (Choose two.)___
A. Linux LVM
B. software RAID
C. GPT/MBR hybrid disks
D. Windows basic volumes
E. Windows dynamic volumes
【多选题】
Which two statements about vCenter HA are correct? (Choose two.)___
A. ESXi 5.5 or later is required.
B. vCenter HA network latency between nodes must be less than 50 ms.
C. NFS datastore is supported.
D. It must be deployed on a 3
E. SXi host cluster with DRS enabled.
【多选题】
An attempt to delete NFS datastore from a ESXi host returns the error: Sysinfo error on operation returned the following status:< Busy> Which two statements could explain this failure? (Choose two.)___
A. NFS datastore is a part of Storage DRS Cluster.
B. NFS.VolumeRemountFrequency value is set to 30.
C. Storage I/O Control is enabled on NFS datastore.
D. NFS datastore has running or registered virtual machines.
【多选题】
An administrator finds that the Microsoft Exchange virtual machines are exhibiting network latency. What two in-guest changes can help decrease latency? (Choose two.)___
A. LRO
B. TSO
C. SR-IOV
D. PVRDMA
【多选题】
Which two types of iSCSI adapters require VMkernel networking configuration? (Choose two.)___
A. dependent hardware
B. in-guest
C. software
D. independent hardware
【多选题】
Which two statements are true for NFS v4.1 firewall behavior? (Choose two.)___
A. It closes port 2049.
B. It sets allowed. All flag to TRUE.
C. It sets allowed. All flag to FALSE.
D. It opens port 2049.
【多选题】
A vSphere Administrator attempts to enable Fault Tolerance for a virtual machine but receives the following error: Secondary VM could not be powered on as there are no compatible hosts that can accommodate it. What two options could cause this error? (Choose two.)___
A. The other ESXi host(s) are in Maintenance Mode.
B. Hardware virtualization is not enabled on the other ESXi host(s).
C. The other ESXi host(s) are in Quarantine Mode.
D. Hardware MMU is enabled on the other
E. SXi host(s).
【多选题】
Storage capabilities be populated in what two ways? (Choose two.)___
A. The administrator can use tags to describe capabilities.
B. Default capabilities are provided by vCenter Server.
C. Datastores can advertise their capabilities through VAAI.
D. Datastores can advertise their capabilities through VASA.
【多选题】
In network troubleshooting it is important to know what upstream switch the ESXi host is connected to. Which two features does ESXi provide to help identify the upstream switch? (Choose two.)___
A. Promiscuous mode
B. DPM
C. LLDP
D. CDP
【多选题】
Virtual Volumes supports which three VMware features? (Choose three.)___
A. Instant Clones
B. Distributed Resource Scheduler
C. Linked Clones
D. vMotion
E. Storage Distributed Resource Scheduler
【多选题】
vSphere DRS helps to balance virtual machines with available resources in a vSphere cluster. What three types of resources can be taken into account for balancing? (Choose three.)___
A. CPU
B. physical NIC saturation of an ESXi host
C. virtual NIC saturation of a virtual machine
D. RAM
E. storage latency
